| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * linux/mm/filemap.c |
| * |
| * Copyright (C) 1994-1999 Linus Torvalds |
| */ |
| |
| /* |
| * This file handles the generic file mmap semantics used by |
| * most "normal" filesystems (but you don't /have/ to use this: |
| * the NFS filesystem used to do this differently, for example) |
| */ |
| #include <linux/export.h> |
| #include <linux/compiler.h> |
| #include <linux/dax.h> |
| #include <linux/fs.h> |
| #include <linux/sched/signal.h> |
| #include <linux/uaccess.h> |
| #include <linux/capability.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/gfp.h> |
| #include <linux/mm.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/mman.h> |
| #include <linux/pagemap.h> |
| #include <linux/file.h> |
| #include <linux/uio.h> |
| #include <linux/error-injection.h> |
| #include <linux/hash.h> |
| #include <linux/writeback.h> |
| #include <linux/backing-dev.h> |
| #include <linux/pagevec.h> |
| #include <linux/security.h> |
| #include <linux/cpuset.h> |
| #include <linux/hugetlb.h> |
| #include <linux/memcontrol.h> |
| #include <linux/shmem_fs.h> |
| #include <linux/rmap.h> |
| #include <linux/delayacct.h> |
| #include <linux/psi.h> |
| #include <linux/ramfs.h> |
| #include <linux/page_idle.h> |
| #include <linux/migrate.h> |
| #include <asm/pgalloc.h> |
| #include <asm/tlbflush.h> |
| #include "internal.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/filemap.h> |
| |
| /* |
| * FIXME: remove all knowledge of the buffer layer from the core VM |
| */ |
| #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
| |
| #include <asm/mman.h> |
| |
| /* |
| * Shared mappings implemented 30.11.1994. It's not fully working yet, |
| * though. |
| * |
| * Shared mappings now work. 15.8.1995 Bruno. |
| * |
| * finished 'unifying' the page and buffer cache and SMP-threaded the |
| * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
| * |
| * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
| */ |
| |
| /* |
| * Lock ordering: |
| * |
| * ->i_mmap_rwsem (truncate_pagecache) |
| * ->private_lock (__free_pte->block_dirty_folio) |
| * ->swap_lock (exclusive_swap_page, others) |
| * ->i_pages lock |
| * |
| * ->i_rwsem |
| * ->invalidate_lock (acquired by fs in truncate path) |
| * ->i_mmap_rwsem (truncate->unmap_mapping_range) |
| * |
| * ->mmap_lock |
| * ->i_mmap_rwsem |
| * ->page_table_lock or pte_lock (various, mainly in memory.c) |
| * ->i_pages lock (arch-dependent flush_dcache_mmap_lock) |
| * |
| * ->mmap_lock |
| * ->invalidate_lock (filemap_fault) |
| * ->lock_page (filemap_fault, access_process_vm) |
| * |
| * ->i_rwsem (generic_perform_write) |
| * ->mmap_lock (fault_in_readable->do_page_fault) |
| * |
| * bdi->wb.list_lock |
| * sb_lock (fs/fs-writeback.c) |
| * ->i_pages lock (__sync_single_inode) |
| * |
| * ->i_mmap_rwsem |
| * ->anon_vma.lock (vma_adjust) |
| * |
| * ->anon_vma.lock |
| * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
| * |
| * ->page_table_lock or pte_lock |
| * ->swap_lock (try_to_unmap_one) |
| * ->private_lock (try_to_unmap_one) |
| * ->i_pages lock (try_to_unmap_one) |
| * ->lruvec->lru_lock (follow_page->mark_page_accessed) |
| * ->lruvec->lru_lock (check_pte_range->isolate_lru_page) |
| * ->private_lock (page_remove_rmap->set_page_dirty) |
| * ->i_pages lock (page_remove_rmap->set_page_dirty) |
| * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) |
| * ->inode->i_lock (page_remove_rmap->set_page_dirty) |
| * ->memcg->move_lock (page_remove_rmap->lock_page_memcg) |
| * bdi.wb->list_lock (zap_pte_range->set_page_dirty) |
| * ->inode->i_lock (zap_pte_range->set_page_dirty) |
| * ->private_lock (zap_pte_range->block_dirty_folio) |
| * |
| * ->i_mmap_rwsem |
| * ->tasklist_lock (memory_failure, collect_procs_ao) |
| */ |
| |
| static void page_cache_delete(struct address_space *mapping, |
| struct folio *folio, void *shadow) |
| { |
| XA_STATE(xas, &mapping->i_pages, folio->index); |
| long nr = 1; |
| |
| mapping_set_update(&xas, mapping); |
| |
| /* hugetlb pages are represented by a single entry in the xarray */ |
| if (!folio_test_hugetlb(folio)) { |
| xas_set_order(&xas, folio->index, folio_order(folio)); |
| nr = folio_nr_pages(folio); |
| } |
| |
| VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| |
| xas_store(&xas, shadow); |
| xas_init_marks(&xas); |
| |
| folio->mapping = NULL; |
| /* Leave page->index set: truncation lookup relies upon it */ |
| mapping->nrpages -= nr; |
| } |
| |
| static void filemap_unaccount_folio(struct address_space *mapping, |
| struct folio *folio) |
| { |
| long nr; |
| |
| VM_BUG_ON_FOLIO(folio_mapped(folio), folio); |
| if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) { |
| pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", |
| current->comm, folio_pfn(folio)); |
| dump_page(&folio->page, "still mapped when deleted"); |
| dump_stack(); |
| add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
| |
| if (mapping_exiting(mapping) && !folio_test_large(folio)) { |
| int mapcount = page_mapcount(&folio->page); |
| |
| if (folio_ref_count(folio) >= mapcount + 2) { |
| /* |
| * All vmas have already been torn down, so it's |
| * a good bet that actually the page is unmapped |
| * and we'd rather not leak it: if we're wrong, |
| * another bad page check should catch it later. |
| */ |
| page_mapcount_reset(&folio->page); |
| folio_ref_sub(folio, mapcount); |
| } |
| } |
| } |
| |
| /* hugetlb folios do not participate in page cache accounting. */ |
| if (folio_test_hugetlb(folio)) |
| return; |
| |
| nr = folio_nr_pages(folio); |
| |
| __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr); |
| if (folio_test_swapbacked(folio)) { |
| __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr); |
| if (folio_test_pmd_mappable(folio)) |
| __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr); |
| } else if (folio_test_pmd_mappable(folio)) { |
| __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr); |
| filemap_nr_thps_dec(mapping); |
| } |
| |
| /* |
| * At this point folio must be either written or cleaned by |
| * truncate. Dirty folio here signals a bug and loss of |
| * unwritten data - on ordinary filesystems. |
| * |
| * But it's harmless on in-memory filesystems like tmpfs; and can |
| * occur when a driver which did get_user_pages() sets page dirty |
| * before putting it, while the inode is being finally evicted. |
| * |
| * Below fixes dirty accounting after removing the folio entirely |
| * but leaves the dirty flag set: it has no effect for truncated |
| * folio and anyway will be cleared before returning folio to |
| * buddy allocator. |
| */ |
| if (WARN_ON_ONCE(folio_test_dirty(folio) && |
| mapping_can_writeback(mapping))) |
| folio_account_cleaned(folio, inode_to_wb(mapping->host)); |
| } |
| |
| /* |
| * Delete a page from the page cache and free it. Caller has to make |
| * sure the page is locked and that nobody else uses it - or that usage |
| * is safe. The caller must hold the i_pages lock. |
| */ |
| void __filemap_remove_folio(struct folio *folio, void *shadow) |
| { |
| struct address_space *mapping = folio->mapping; |
| |
| trace_mm_filemap_delete_from_page_cache(folio); |
| filemap_unaccount_folio(mapping, folio); |
| page_cache_delete(mapping, folio, shadow); |
| } |
| |
| void filemap_free_folio(struct address_space *mapping, struct folio *folio) |
| { |
| void (*free_folio)(struct folio *); |
| int refs = 1; |
| |
| free_folio = mapping->a_ops->free_folio; |
| if (free_folio) |
| free_folio(folio); |
| |
| if (folio_test_large(folio) && !folio_test_hugetlb(folio)) |
| refs = folio_nr_pages(folio); |
| folio_put_refs(folio, refs); |
| } |
| |
| /** |
| * filemap_remove_folio - Remove folio from page cache. |
| * @folio: The folio. |
| * |
| * This must be called only on folios that are locked and have been |
| * verified to be in the page cache. It will never put the folio into |
| * the free list because the caller has a reference on the page. |
| */ |
| void filemap_remove_folio(struct folio *folio) |
| { |
| struct address_space *mapping = folio->mapping; |
| |
| BUG_ON(!folio_test_locked(folio)); |
| spin_lock(&mapping->host->i_lock); |
| xa_lock_irq(&mapping->i_pages); |
| __filemap_remove_folio(folio, NULL); |
| xa_unlock_irq(&mapping->i_pages); |
| if (mapping_shrinkable(mapping)) |
| inode_add_lru(mapping->host); |
| spin_unlock(&mapping->host->i_lock); |
| |
| filemap_free_folio(mapping, folio); |
| } |
| |
| /* |
| * page_cache_delete_batch - delete several folios from page cache |
| * @mapping: the mapping to which folios belong |
| * @fbatch: batch of folios to delete |
| * |
| * The function walks over mapping->i_pages and removes folios passed in |
| * @fbatch from the mapping. The function expects @fbatch to be sorted |
| * by page index and is optimised for it to be dense. |
| * It tolerates holes in @fbatch (mapping entries at those indices are not |
| * modified). |
| * |
| * The function expects the i_pages lock to be held. |
| */ |
| static void page_cache_delete_batch(struct address_space *mapping, |
| struct folio_batch *fbatch) |
| { |
| XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index); |
| long total_pages = 0; |
| int i = 0; |
| struct folio *folio; |
| |
| mapping_set_update(&xas, mapping); |
| xas_for_each(&xas, folio, ULONG_MAX) { |
| if (i >= folio_batch_count(fbatch)) |
| break; |
| |
| /* A swap/dax/shadow entry got inserted? Skip it. */ |
| if (xa_is_value(folio)) |
| continue; |
| /* |
| * A page got inserted in our range? Skip it. We have our |
| * pages locked so they are protected from being removed. |
| * If we see a page whose index is higher than ours, it |
| * means our page has been removed, which shouldn't be |
| * possible because we're holding the PageLock. |
| */ |
| if (folio != fbatch->folios[i]) { |
| VM_BUG_ON_FOLIO(folio->index > |
| fbatch->folios[i]->index, folio); |
| continue; |
| } |
| |
| WARN_ON_ONCE(!folio_test_locked(folio)); |
| |
| folio->mapping = NULL; |
| /* Leave folio->index set: truncation lookup relies on it */ |
| |
| i++; |
| xas_store(&xas, NULL); |
| total_pages += folio_nr_pages(folio); |
| } |
| mapping->nrpages -= total_pages; |
| } |
| |
| void delete_from_page_cache_batch(struct address_space *mapping, |
| struct folio_batch *fbatch) |
| { |
| int i; |
| |
| if (!folio_batch_count(fbatch)) |
| return; |
| |
| spin_lock(&mapping->host->i_lock); |
| xa_lock_irq(&mapping->i_pages); |
| for (i = 0; i < folio_batch_count(fbatch); i++) { |
| struct folio *folio = fbatch->folios[i]; |
| |
| trace_mm_filemap_delete_from_page_cache(folio); |
| filemap_unaccount_folio(mapping, folio); |
| } |
| page_cache_delete_batch(mapping, fbatch); |
| xa_unlock_irq(&mapping->i_pages); |
| if (mapping_shrinkable(mapping)) |
| inode_add_lru(mapping->host); |
| spin_unlock(&mapping->host->i_lock); |
| |
| for (i = 0; i < folio_batch_count(fbatch); i++) |
| filemap_free_folio(mapping, fbatch->folios[i]); |
| } |
| |
| int filemap_check_errors(struct address_space *mapping) |
| { |
| int ret = 0; |
| /* Check for outstanding write errors */ |
| if (test_bit(AS_ENOSPC, &mapping->flags) && |
| test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
| ret = -ENOSPC; |
| if (test_bit(AS_EIO, &mapping->flags) && |
| test_and_clear_bit(AS_EIO, &mapping->flags)) |
| ret = -EIO; |
| return ret; |
| } |
| EXPORT_SYMBOL(filemap_check_errors); |
| |
| static int filemap_check_and_keep_errors(struct address_space *mapping) |
| { |
| /* Check for outstanding write errors */ |
| if (test_bit(AS_EIO, &mapping->flags)) |
| return -EIO; |
| if (test_bit(AS_ENOSPC, &mapping->flags)) |
| return -ENOSPC; |
| return 0; |
| } |
| |
| /** |
| * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range |
| * @mapping: address space structure to write |
| * @wbc: the writeback_control controlling the writeout |
| * |
| * Call writepages on the mapping using the provided wbc to control the |
| * writeout. |
| * |
| * Return: %0 on success, negative error code otherwise. |
| */ |
| int filemap_fdatawrite_wbc(struct address_space *mapping, |
| struct writeback_control *wbc) |
| { |
| int ret; |
| |
| if (!mapping_can_writeback(mapping) || |
| !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) |
| return 0; |
| |
| wbc_attach_fdatawrite_inode(wbc, mapping->host); |
| ret = do_writepages(mapping, wbc); |
| wbc_detach_inode(wbc); |
| return ret; |
| } |
| EXPORT_SYMBOL(filemap_fdatawrite_wbc); |
| |
| /** |
| * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
| * @mapping: address space structure to write |
| * @start: offset in bytes where the range starts |
| * @end: offset in bytes where the range ends (inclusive) |
| * @sync_mode: enable synchronous operation |
| * |
| * Start writeback against all of a mapping's dirty pages that lie |
| * within the byte offsets <start, end> inclusive. |
| * |
| * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
| * opposed to a regular memory cleansing writeback. The difference between |
| * these two operations is that if a dirty page/buffer is encountered, it must |
| * be waited upon, and not just skipped over. |
| * |
| * Return: %0 on success, negative error code otherwise. |
| */ |
| int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| loff_t end, int sync_mode) |
| { |
| struct writeback_control wbc = { |
| .sync_mode = sync_mode, |
| .nr_to_write = LONG_MAX, |
| .range_start = start, |
| .range_end = end, |
| }; |
| |
| return filemap_fdatawrite_wbc(mapping, &wbc); |
| } |
| |
| static inline int __filemap_fdatawrite(struct address_space *mapping, |
| int sync_mode) |
| { |
| return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
| } |
| |
| int filemap_fdatawrite(struct address_space *mapping) |
| { |
| return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
| } |
| EXPORT_SYMBOL(filemap_fdatawrite); |
| |
| int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| loff_t end) |
| { |
| return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
| } |
| EXPORT_SYMBOL(filemap_fdatawrite_range); |
| |
| /** |
| * filemap_flush - mostly a non-blocking flush |
| * @mapping: target address_space |
| * |
| * This is a mostly non-blocking flush. Not suitable for data-integrity |
| * purposes - I/O may not be started against all dirty pages. |
| * |
| * Return: %0 on success, negative error code otherwise. |
| */ |
| int filemap_flush(struct address_space *mapping) |
| { |
| return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
| } |
| EXPORT_SYMBOL(filemap_flush); |
| |
| /** |
| * filemap_range_has_page - check if a page exists in range. |
| * @mapping: address space within which to check |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Find at least one page in the range supplied, usually used to check if |
| * direct writing in this range will trigger a writeback. |
| * |
| * Return: %true if at least one page exists in the specified range, |
| * %false otherwise. |
| */ |
| bool filemap_range_has_page(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| struct page *page; |
| XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
| pgoff_t max = end_byte >> PAGE_SHIFT; |
| |
| if (end_byte < start_byte) |
| return false; |
| |
| rcu_read_lock(); |
| for (;;) { |
| page = xas_find(&xas, max); |
| if (xas_retry(&xas, page)) |
| continue; |
| /* Shadow entries don't count */ |
| if (xa_is_value(page)) |
| continue; |
| /* |
| * We don't need to try to pin this page; we're about to |
| * release the RCU lock anyway. It is enough to know that |
| * there was a page here recently. |
| */ |
| break; |
| } |
| rcu_read_unlock(); |
| |
| return page != NULL; |
| } |
| EXPORT_SYMBOL(filemap_range_has_page); |
| |
| static void __filemap_fdatawait_range(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| pgoff_t index = start_byte >> PAGE_SHIFT; |
| pgoff_t end = end_byte >> PAGE_SHIFT; |
| struct pagevec pvec; |
| int nr_pages; |
| |
| if (end_byte < start_byte) |
| return; |
| |
| pagevec_init(&pvec); |
| while (index <= end) { |
| unsigned i; |
| |
| nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, |
| end, PAGECACHE_TAG_WRITEBACK); |
| if (!nr_pages) |
| break; |
| |
| for (i = 0; i < nr_pages; i++) { |
| struct page *page = pvec.pages[i]; |
| |
| wait_on_page_writeback(page); |
| ClearPageError(page); |
| } |
| pagevec_release(&pvec); |
| cond_resched(); |
| } |
| } |
| |
| /** |
| * filemap_fdatawait_range - wait for writeback to complete |
| * @mapping: address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the given address space |
| * in the given range and wait for all of them. Check error status of |
| * the address space and return it. |
| * |
| * Since the error status of the address space is cleared by this function, |
| * callers are responsible for checking the return value and handling and/or |
| * reporting the error. |
| * |
| * Return: error status of the address space. |
| */ |
| int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
| loff_t end_byte) |
| { |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return filemap_check_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_range); |
| |
| /** |
| * filemap_fdatawait_range_keep_errors - wait for writeback to complete |
| * @mapping: address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the given address space in the |
| * given range and wait for all of them. Unlike filemap_fdatawait_range(), |
| * this function does not clear error status of the address space. |
| * |
| * Use this function if callers don't handle errors themselves. Expected |
| * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| * fsfreeze(8) |
| */ |
| int filemap_fdatawait_range_keep_errors(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return filemap_check_and_keep_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors); |
| |
| /** |
| * file_fdatawait_range - wait for writeback to complete |
| * @file: file pointing to address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the address space that file |
| * refers to, in the given range and wait for all of them. Check error |
| * status of the address space vs. the file->f_wb_err cursor and return it. |
| * |
| * Since the error status of the file is advanced by this function, |
| * callers are responsible for checking the return value and handling and/or |
| * reporting the error. |
| * |
| * Return: error status of the address space vs. the file->f_wb_err cursor. |
| */ |
| int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte) |
| { |
| struct address_space *mapping = file->f_mapping; |
| |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return file_check_and_advance_wb_err(file); |
| } |
| EXPORT_SYMBOL(file_fdatawait_range); |
| |
| /** |
| * filemap_fdatawait_keep_errors - wait for writeback without clearing errors |
| * @mapping: address space structure to wait for |
| * |
| * Walk the list of under-writeback pages of the given address space |
| * and wait for all of them. Unlike filemap_fdatawait(), this function |
| * does not clear error status of the address space. |
| * |
| * Use this function if callers don't handle errors themselves. Expected |
| * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| * fsfreeze(8) |
| * |
| * Return: error status of the address space. |
| */ |
| int filemap_fdatawait_keep_errors(struct address_space *mapping) |
| { |
| __filemap_fdatawait_range(mapping, 0, LLONG_MAX); |
| return filemap_check_and_keep_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_keep_errors); |
| |
| /* Returns true if writeback might be needed or already in progress. */ |
| static bool mapping_needs_writeback(struct address_space *mapping) |
| { |
| return mapping->nrpages; |
| } |
| |
| bool filemap_range_has_writeback(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
| pgoff_t max = end_byte >> PAGE_SHIFT; |
| struct folio *folio; |
| |
| if (end_byte < start_byte) |
| return false; |
| |
| rcu_read_lock(); |
| xas_for_each(&xas, folio, max) { |
| if (xas_retry(&xas, folio)) |
| continue; |
| if (xa_is_value(folio)) |
| continue; |
| if (folio_test_dirty(folio) || folio_test_locked(folio) || |
| folio_test_writeback(folio)) |
| break; |
| } |
| rcu_read_unlock(); |
| return folio != NULL; |
| } |
| EXPORT_SYMBOL_GPL(filemap_range_has_writeback); |
| |
| /** |
| * filemap_write_and_wait_range - write out & wait on a file range |
| * @mapping: the address_space for the pages |
| * @lstart: offset in bytes where the range starts |
| * @lend: offset in bytes where the range ends (inclusive) |
| * |
| * Write out and wait upon file offsets lstart->lend, inclusive. |
| * |
| * Note that @lend is inclusive (describes the last byte to be written) so |
| * that this function can be used to write to the very end-of-file (end = -1). |
| * |
| * Return: error status of the address space. |
| */ |
| int filemap_write_and_wait_range(struct address_space *mapping, |
| loff_t lstart, loff_t lend) |
| { |
| int err = 0, err2; |
| |
| if (mapping_needs_writeback(mapping)) { |
| err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| WB_SYNC_ALL); |
| /* |
| * Even if the above returned error, the pages may be |
| * written partially (e.g. -ENOSPC), so we wait for it. |
| * But the -EIO is special case, it may indicate the worst |
| * thing (e.g. bug) happened, so we avoid waiting for it. |
| */ |
| if (err != -EIO) |
| __filemap_fdatawait_range(mapping, lstart, lend); |
| } |
| err2 = filemap_check_errors(mapping); |
| if (!err) |
| err = err2; |
| return err; |
| } |
| EXPORT_SYMBOL(filemap_write_and_wait_range); |
| |
| void __filemap_set_wb_err(struct address_space *mapping, int err) |
| { |
| errseq_t eseq = errseq_set(&mapping->wb_err, err); |
| |
| trace_filemap_set_wb_err(mapping, eseq); |
| } |
| EXPORT_SYMBOL(__filemap_set_wb_err); |
| |
| /** |
| * file_check_and_advance_wb_err - report wb error (if any) that was previously |
| * and advance wb_err to current one |
| * @file: struct file on which the error is being reported |
| * |
| * When userland calls fsync (or something like nfsd does the equivalent), we |
| * want to report any writeback errors that occurred since the last fsync (or |
| * since the file was opened if there haven't been any). |
| * |
| * Grab the wb_err from the mapping. If it matches what we have in the file, |
| * then just quickly return 0. The file is all caught up. |
| * |
| * If it doesn't match, then take the mapping value, set the "seen" flag in |
| * it and try to swap it into place. If it works, or another task beat us |
| * to it with the new value, then update the f_wb_err and return the error |
| * portion. The error at this point must be reported via proper channels |
| * (a'la fsync, or NFS COMMIT operation, etc.). |
| * |
| * While we handle mapping->wb_err with atomic operations, the f_wb_err |
| * value is protected by the f_lock since we must ensure that it reflects |
| * the latest value swapped in for this file descriptor. |
| * |
| * Return: %0 on success, negative error code otherwise. |
| */ |
| int file_check_and_advance_wb_err(struct file *file) |
| { |
| int err = 0; |
| errseq_t old = READ_ONCE(file->f_wb_err); |
| struct address_space *mapping = file->f_mapping; |
| |
| /* Locklessly handle the common case where nothing has changed */ |
| if (errseq_check(&mapping->wb_err, old)) { |
| /* Something changed, must use slow path */ |
| spin_lock(&file->f_lock); |
| old = file->f_wb_err; |
| err = errseq_check_and_advance(&mapping->wb_err, |
| &file->f_wb_err); |
| trace_file_check_and_advance_wb_err(file, old); |
| spin_unlock(&file->f_lock); |
| } |
| |
| /* |
| * We're mostly using this function as a drop in replacement for |
| * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect |
| * that the legacy code would have had on these flags. |
| */ |
| clear_bit(AS_EIO, &mapping->flags); |
| clear_bit(AS_ENOSPC, &mapping->flags); |
| return err; |
| } |
| EXPORT_SYMBOL(file_check_and_advance_wb_err); |
| |
| /** |
| * file_write_and_wait_range - write out & wait on a file range |
| * @file: file pointing to address_space with pages |
| * @lstart: offset in bytes where the range starts |
| * @lend: offset in bytes where the range ends (inclusive) |
| * |
| * Write out and wait upon file offsets lstart->lend, inclusive. |
| * |
| * Note that @lend is inclusive (describes the last byte to be written) so |
| * that this function can be used to write to the very end-of-file (end = -1). |
| * |
| * After writing out and waiting on the data, we check and advance the |
| * f_wb_err cursor to the latest value, and return any errors detected there. |
| * |
| * Return: %0 on success, negative error code otherwise. |
| */ |
| int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend) |
| { |
| int err = 0, err2; |
| struct address_space *mapping = file->f_mapping; |
| |
| if (mapping_needs_writeback(mapping)) { |
| err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| WB_SYNC_ALL); |
| /* See comment of filemap_write_and_wait() */ |
| if (err != -EIO) |
| __filemap_fdatawait_range(mapping, lstart, lend); |
| } |
| err2 = file_check_and_advance_wb_err(file); |
| if (!err) |
| err = err2; |
| return err; |
| } |
| EXPORT_SYMBOL(file_write_and_wait_range); |
| |
| /** |
| * replace_page_cache_page - replace a pagecache page with a new one |
| * @old: page to be replaced |
| * @new: page to replace with |
| * |
| * This function replaces a page in the pagecache with a new one. On |
| * success it acquires the pagecache reference for the new page and |
| * drops it for the old page. Both the old and new pages must be |
| * locked. This function does not add the new page to the LRU, the |
| * caller must do that. |
| * |
| * The remove + add is atomic. This function cannot fail. |
| */ |
| void replace_page_cache_page(struct page *old, struct page *new) |
| { |
| struct folio *fold = page_folio(old); |
| struct folio *fnew = page_folio(new); |
| struct address_space *mapping = old->mapping; |
| void (*free_folio)(struct folio *) = mapping->a_ops->free_folio; |
| pgoff_t offset = old->index; |
| XA_STATE(xas, &mapping->i_pages, offset); |
| |
| VM_BUG_ON_PAGE(!PageLocked(old), old); |
| VM_BUG_ON_PAGE(!PageLocked(new), new); |
| VM_BUG_ON_PAGE(new->mapping, new); |
| |
| get_page(new); |
| new->mapping = mapping; |
| new->index = offset; |
| |
| mem_cgroup_migrate(fold, fnew); |
| |
| xas_lock_irq(&xas); |
| xas_store(&xas, new); |
| |
| old->mapping = NULL; |
| /* hugetlb pages do not participate in page cache accounting. */ |
| if (!PageHuge(old)) |
| __dec_lruvec_page_state(old, NR_FILE_PAGES); |
| if (!PageHuge(new)) |
| __inc_lruvec_page_state(new, NR_FILE_PAGES); |
| if (PageSwapBacked(old)) |
| __dec_lruvec_page_state(old, NR_SHMEM); |
| if (PageSwapBacked(new)) |
| __inc_lruvec_page_state(new, NR_SHMEM); |
| xas_unlock_irq(&xas); |
| if (free_folio) |
| free_folio(fold); |
| folio_put(fold); |
| } |
| EXPORT_SYMBOL_GPL(replace_page_cache_page); |
| |
| noinline int __filemap_add_folio(struct address_space *mapping, |
| struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp) |
| { |
| XA_STATE(xas, &mapping->i_pages, index); |
| int huge = folio_test_hugetlb(folio); |
| bool charged = false; |
| long nr = 1; |
| |
| VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio); |
| mapping_set_update(&xas, mapping); |
| |
| if (!huge) { |
| int error = mem_cgroup_charge(folio, NULL, gfp); |
| VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio); |
| if (error) |
| return error; |
| charged = true; |
| xas_set_order(&xas, index, folio_order(folio)); |
| nr = folio_nr_pages(folio); |
| } |
| |
| gfp &= GFP_RECLAIM_MASK; |
| folio_ref_add(folio, nr); |
| folio->mapping = mapping; |
| folio->index = xas.xa_index; |
| |
| do { |
| unsigned int order = xa_get_order(xas.xa, xas.xa_index); |
| void *entry, *old = NULL; |
| |
| if (order > folio_order(folio)) |
| xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index), |
| order, gfp); |
| xas_lock_irq(&xas); |
| xas_for_each_conflict(&xas, entry) { |
| old = entry; |
| if (!xa_is_value(entry)) { |
| xas_set_err(&xas, -EEXIST); |
| goto unlock; |
| } |
| } |
| |
| if (old) { |
| if (shadowp) |
| *shadowp = old; |
| /* entry may have been split before we acquired lock */ |
| order = xa_get_order(xas.xa, xas.xa_index); |
| if (order > folio_order(folio)) { |
| /* How to handle large swap entries? */ |
| BUG_ON(shmem_mapping(mapping)); |
| xas_split(&xas, old, order); |
| xas_reset(&xas); |
| } |
| } |
| |
| xas_store(&xas, folio); |
| if (xas_error(&xas)) |
| goto unlock; |
| |
| mapping->nrpages += nr; |
| |
| /* hugetlb pages do not participate in page cache accounting */ |
| if (!huge) { |
| __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr); |
| if (folio_test_pmd_mappable(folio)) |
| __lruvec_stat_mod_folio(folio, |
| NR_FILE_THPS, nr); |
| } |
| unlock: |
| xas_unlock_irq(&xas); |
| } while (xas_nomem(&xas, gfp)); |
| |
| if (xas_error(&xas)) |
| goto error; |
| |
| trace_mm_filemap_add_to_page_cache(folio); |
| return 0; |
| error: |
| if (charged) |
| mem_cgroup_uncharge(folio); |
| folio->mapping = NULL; |
| /* Leave page->index set: truncation relies upon it */ |
| folio_put_refs(folio, nr); |
| return xas_error(&xas); |
| } |
| ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO); |
| |
| int filemap_add_folio(struct address_space *mapping, struct folio *folio, |
| pgoff_t index, gfp_t gfp) |
| { |
| void *shadow = NULL; |
| int ret; |
| |
| __folio_set_locked(folio); |
| ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow); |
| if (unlikely(ret)) |
| __folio_clear_locked(folio); |
| else { |
| /* |
| * The folio might have been evicted from cache only |
| * recently, in which case it should be activated like |
| * any other repeatedly accessed folio. |
| * The exception is folios getting rewritten; evicting other |
| * data from the working set, only to cache data that will |
| * get overwritten with something else, is a waste of memory. |
| */ |
| WARN_ON_ONCE(folio_test_active(folio)); |
| if (!(gfp & __GFP_WRITE) && shadow) |
| workingset_refault(folio, shadow); |
| folio_add_lru(folio); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(filemap_add_folio); |
| |
| #ifdef CONFIG_NUMA |
| struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order) |
| { |
| int n; |
| struct folio *folio; |
| |
| if (cpuset_do_page_mem_spread()) { |
| unsigned int cpuset_mems_cookie; |
| do { |
| cpuset_mems_cookie = read_mems_allowed_begin(); |
| n = cpuset_mem_spread_node(); |
| folio = __folio_alloc_node(gfp, order, n); |
| } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie)); |
| |
| return folio; |
| } |
| return folio_alloc(gfp, order); |
| } |
| EXPORT_SYMBOL(filemap_alloc_folio); |
| #endif |
| |
| /* |
| * filemap_invalidate_lock_two - lock invalidate_lock for two mappings |
| * |
| * Lock exclusively invalidate_lock of any passed mapping that is not NULL. |
| * |
| * @mapping1: the first mapping to lock |
| * @mapping2: the second mapping to lock |
| */ |
| void filemap_invalidate_lock_two(struct address_space *mapping1, |
| struct address_space *mapping2) |
| { |
| if (mapping1 > mapping2) |
| swap(mapping1, mapping2); |
| if (mapping1) |
| down_write(&mapping1->invalidate_lock); |
| if (mapping2 && mapping1 != mapping2) |
| down_write_nested(&mapping2->invalidate_lock, 1); |
| } |
| EXPORT_SYMBOL(filemap_invalidate_lock_two); |
| |
| /* |
| * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings |
| * |
| * Unlock exclusive invalidate_lock of any passed mapping that is not NULL. |
| * |
| * @mapping1: the first mapping to unlock |
| * @mapping2: the second mapping to unlock |
| */ |
| void filemap_invalidate_unlock_two(struct address_space *mapping1, |
| struct address_space *mapping2) |
| { |
| if (mapping1) |
| up_write(&mapping1->invalidate_lock); |
| if (mapping2 && mapping1 != mapping2) |
| up_write(&mapping2->invalidate_lock); |
| } |
| EXPORT_SYMBOL(filemap_invalidate_unlock_two); |
| |
| /* |
| * In order to wait for pages to become available there must be |
| * waitqueues associated with pages. By using a hash table of |
| * waitqueues where the bucket discipline is to maintain all |
| * waiters on the same queue and wake all when any of the pages |
| * become available, and for the woken contexts to check to be |
| * sure the appropriate page became available, this saves space |
| * at a cost of "thundering herd" phenomena during rare hash |
| * collisions. |
| */ |
| #define PAGE_WAIT_TABLE_BITS 8 |
| #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) |
| static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; |
| |
| static wait_queue_head_t *folio_waitqueue(struct folio *folio) |
| { |
| return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)]; |
| } |
| |
| void __init pagecache_init(void) |
| { |
| int i; |
| |
| for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) |
| init_waitqueue_head(&folio_wait_table[i]); |
| |
| page_writeback_init(); |
| } |
| |
| /* |
| * The page wait code treats the "wait->flags" somewhat unusually, because |
| * we have multiple different kinds of waits, not just the usual "exclusive" |
| * one. |
| * |
| * We have: |
| * |
| * (a) no special bits set: |
| * |
| * We're just waiting for the bit to be released, and when a waker |
| * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up, |
| * and remove it from the wait queue. |
| * |
| * Simple and straightforward. |
| * |
| * (b) WQ_FLAG_EXCLUSIVE: |
| * |
| * The waiter is waiting to get the lock, and only one waiter should |
| * be woken up to avoid any thundering herd behavior. We'll set the |
| * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue. |
| * |
| * This is the traditional exclusive wait. |
| * |
| * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM: |
| * |
| * The waiter is waiting to get the bit, and additionally wants the |
| * lock to be transferred to it for fair lock behavior. If the lock |
| * cannot be taken, we stop walking the wait queue without waking |
| * the waiter. |
| * |
| * This is the "fair lock handoff" case, and in addition to setting |
| * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see |
| * that it now has the lock. |
| */ |
| static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) |
| { |
| unsigned int flags; |
| struct wait_page_key *key = arg; |
| struct wait_page_queue *wait_page |
| = container_of(wait, struct wait_page_queue, wait); |
| |
| if (!wake_page_match(wait_page, key)) |
| return 0; |
| |
| /* |
| * If it's a lock handoff wait, we get the bit for it, and |
| * stop walking (and do not wake it up) if we can't. |
| */ |
| flags = wait->flags; |
| if (flags & WQ_FLAG_EXCLUSIVE) { |
| if (test_bit(key->bit_nr, &key->folio->flags)) |
| return -1; |
| if (flags & WQ_FLAG_CUSTOM) { |
| if (test_and_set_bit(key->bit_nr, &key->folio->flags)) |
| return -1; |
| flags |= WQ_FLAG_DONE; |
| } |
| } |
| |
| /* |
| * We are holding the wait-queue lock, but the waiter that |
| * is waiting for this will be checking the flags without |
| * any locking. |
| * |
| * So update the flags atomically, and wake up the waiter |
| * afterwards to avoid any races. This store-release pairs |
| * with the load-acquire in folio_wait_bit_common(). |
| */ |
| smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN); |
| wake_up_state(wait->private, mode); |
| |
| /* |
| * Ok, we have successfully done what we're waiting for, |
| * and we can unconditionally remove the wait entry. |
| * |
| * Note that this pairs with the "finish_wait()" in the |
| * waiter, and has to be the absolute last thing we do. |
| * After this list_del_init(&wait->entry) the wait entry |
| * might be de-allocated and the process might even have |
| * exited. |
| */ |
| list_del_init_careful(&wait->entry); |
| return (flags & WQ_FLAG_EXCLUSIVE) != 0; |
| } |
| |
| static void folio_wake_bit(struct folio *folio, int bit_nr) |
| { |
| wait_queue_head_t *q = folio_waitqueue(folio); |
| struct wait_page_key key; |
| unsigned long flags; |
| wait_queue_entry_t bookmark; |
| |
| key.folio = folio; |
| key.bit_nr = bit_nr; |
| key.page_match = 0; |
| |
| bookmark.flags = 0; |
| bookmark.private = NULL; |
| bookmark.func = NULL; |
| INIT_LIST_HEAD(&bookmark.entry); |
| |
| spin_lock_irqsave(&q->lock, flags); |
| __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| |
| while (bookmark.flags & WQ_FLAG_BOOKMARK) { |
| /* |
| * Take a breather from holding the lock, |
| * allow pages that finish wake up asynchronously |
| * to acquire the lock and remove themselves |
| * from wait queue |
| */ |
| spin_unlock_irqrestore(&q->lock, flags); |
| cpu_relax(); |
| spin_lock_irqsave(&q->lock, flags); |
| __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| } |
| |
| /* |
| * It's possible to miss clearing waiters here, when we woke our page |
| * waiters, but the hashed waitqueue has waiters for other pages on it. |
| * That's okay, it's a rare case. The next waker will clear it. |
| * |
| * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE, |
| * other), the flag may be cleared in the course of freeing the page; |
| * but that is not required for correctness. |
| */ |
| if (!waitqueue_active(q) || !key.page_match) |
| folio_clear_waiters(folio); |
| |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| |
| static void folio_wake(struct folio *folio, int bit) |
| { |
| if (!folio_test_waiters(folio)) |
| return; |
| folio_wake_bit(folio, bit); |
| } |
| |
| /* |
| * A choice of three behaviors for folio_wait_bit_common(): |
| */ |
| enum behavior { |
| EXCLUSIVE, /* Hold ref to page and take the bit when woken, like |
| * __folio_lock() waiting on then setting PG_locked. |
| */ |
| SHARED, /* Hold ref to page and check the bit when woken, like |
| * folio_wait_writeback() waiting on PG_writeback. |
| */ |
| DROP, /* Drop ref to page before wait, no check when woken, |
| * like folio_put_wait_locked() on PG_locked. |
| */ |
| }; |
| |
| /* |
| * Attempt to check (or get) the folio flag, and mark us done |
| * if successful. |
| */ |
| static inline bool folio_trylock_flag(struct folio *folio, int bit_nr, |
| struct wait_queue_entry *wait) |
| { |
| if (wait->flags & WQ_FLAG_EXCLUSIVE) { |
| if (test_and_set_bit(bit_nr, &folio->flags)) |
| return false; |
| } else if (test_bit(bit_nr, &folio->flags)) |
| return false; |
| |
| wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE; |
| return true; |
| } |
| |
| /* How many times do we accept lock stealing from under a waiter? */ |
| int sysctl_page_lock_unfairness = 5; |
| |
| static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, |
| int state, enum behavior behavior) |
| { |
| wait_queue_head_t *q = folio_waitqueue(folio); |
| int unfairness = sysctl_page_lock_unfairness; |
| struct wait_page_queue wait_page; |
| wait_queue_entry_t *wait = &wait_page.wait; |
| bool thrashing = false; |
| unsigned long pflags; |
| bool in_thrashing; |
| |
| if (bit_nr == PG_locked && |
| !folio_test_uptodate(folio) && folio_test_workingset(folio)) { |
| delayacct_thrashing_start(&in_thrashing); |
| psi_memstall_enter(&pflags); |
| thrashing = true; |
| } |
| |
| init_wait(wait); |
| wait->func = wake_page_function; |
| wait_page.folio = folio; |
| wait_page.bit_nr = bit_nr; |
| |
| repeat: |
| wait->flags = 0; |
| if (behavior == EXCLUSIVE) { |
| wait->flags = WQ_FLAG_EXCLUSIVE; |
| if (--unfairness < 0) |
| wait->flags |= WQ_FLAG_CUSTOM; |
| } |
| |
| /* |
| * Do one last check whether we can get the |
| * page bit synchronously. |
| * |
| * Do the folio_set_waiters() marking before that |
| * to let any waker we _just_ missed know they |
| * need to wake us up (otherwise they'll never |
| * even go to the slow case that looks at the |
| * page queue), and add ourselves to the wait |
| * queue if we need to sleep. |
| * |
| * This part needs to be done under the queue |
| * lock to avoid races. |
| */ |
| spin_lock_irq(&q->lock); |
| folio_set_waiters(folio); |
| if (!folio_trylock_flag(folio, bit_nr, wait)) |
| __add_wait_queue_entry_tail(q, wait); |
| spin_unlock_irq(&q->lock); |
| |
| /* |
| * From now on, all the logic will be based on |
| * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to |
| * see whether the page bit testing has already |
| * been done by the wake function. |
| * |
| * We can drop our reference to the folio. |
| */ |
| if (behavior == DROP) |
| folio_put(folio); |
| |
| /* |
| * Note that until the "finish_wait()", or until |
| * we see the WQ_FLAG_WOKEN flag, we need to |
| * be very careful with the 'wait->flags', because |
| * we may race with a waker that sets them. |
| */ |
| for (;;) { |
| unsigned int flags; |
| |
| set_current_state(state); |
| |
| /* Loop until we've been woken or interrupted */ |
| flags = smp_load_acquire(&wait->flags); |
| if (!(flags & WQ_FLAG_WOKEN)) { |
| if (signal_pending_state(state, current)) |
| break; |
| |
| io_schedule(); |
| continue; |
| } |
| |
| /* If we were non-exclusive, we're done */ |
| if (behavior != EXCLUSIVE) |
| break; |
| |
| /* If the waker got the lock for us, we're done */ |
| if (flags & WQ_FLAG_DONE) |
| break; |
| |
| /* |
| * Otherwise, if we're getting the lock, we need to |
| * try to get it ourselves. |
| * |
| * And if that fails, we'll have to retry this all. |
| */ |
| if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0)))) |
| goto repeat; |
| |
| wait->flags |= WQ_FLAG_DONE; |
| break; |
| } |
| |
| /* |
| * If a signal happened, this 'finish_wait()' may remove the last |
| * waiter from the wait-queues, but the folio waiters bit will remain |
| * set. That's ok. The next wakeup will take care of it, and trying |
| * to do it here would be difficult and prone to races. |
| */ |
| finish_wait(q, wait); |
| |
| if (thrashing) { |
| delayacct_thrashing_end(&in_thrashing); |
| psi_memstall_leave(&pflags); |
| } |
| |
| /* |
| * NOTE! The wait->flags weren't stable until we've done the |
| * 'finish_wait()', and we could have exited the loop above due |
| * to a signal, and had a wakeup event happen after the signal |
| * test but before the 'finish_wait()'. |
| * |
| * So only after the finish_wait() can we reliably determine |
| * if we got woken up or not, so we can now figure out the final |
| * return value based on that state without races. |
| * |
| * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive |
| * waiter, but an exclusive one requires WQ_FLAG_DONE. |
| */ |
| if (behavior == EXCLUSIVE) |
| return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR; |
| |
| return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR; |
| } |
| |
| #ifdef CONFIG_MIGRATION |
| /** |
| * migration_entry_wait_on_locked - Wait for a migration entry to be removed |
| * @entry: migration swap entry. |
| * @ptep: mapped pte pointer. Will return with the ptep unmapped. Only required |
| * for pte entries, pass NULL for pmd entries. |
| * @ptl: already locked ptl. This function will drop the lock. |
| * |
| * Wait for a migration entry referencing the given page to be removed. This is |
| * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except |
| * this can be called without taking a reference on the page. Instead this |
| * should be called while holding the ptl for the migration entry referencing |
| * the page. |
| * |
| * Returns after unmapping and unlocking the pte/ptl with pte_unmap_unlock(). |
| * |
| * This follows the same logic as folio_wait_bit_common() so see the comments |
| * there. |
| */ |
| void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep, |
| spinlock_t *ptl) |
| { |
| struct wait_page_queue wait_page; |
| wait_queue_entry_t *wait = &wait_page.wait; |
| bool thrashing = false; |
| unsigned long pflags; |
| bool in_thrashing; |
| wait_queue_head_t *q; |
| struct folio *folio = page_folio(pfn_swap_entry_to_page(entry)); |
| |
| q = folio_waitqueue(folio); |
| if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) { |
| delayacct_thrashing_start(&in_thrashing); |
| psi_memstall_enter(&pflags); |
| thrashing = true; |
| } |
| |
| init_wait(wait); |
| wait->func = wake_page_function; |
| wait_page.folio = folio; |
| wait_page.bit_nr = PG_locked; |
| wait->flags = 0; |
| |
| spin_lock_irq(&q->lock); |
| folio_set_waiters(folio); |
| if (!folio_trylock_flag(folio, PG_locked, wait)) |
| __add_wait_queue_entry_tail(q, wait); |
| spin_unlock_irq(&q->lock); |
| |
| /* |
| * If a migration entry exists for the page the migration path must hold |
| * a valid reference to the page, and it must take the ptl to remove the |
| * migration entry. So the page is valid until the ptl is dropped. |
| */ |
| if (ptep) |
| pte_unmap_unlock(ptep, ptl); |
| else |
| spin_unlock(ptl); |
| |
| for (;;) { |
| unsigned int flags; |
| |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| |
| /* Loop until we've been woken or interrupted */ |
| flags = smp_load_acquire(&wait->flags); |
| if (!(flags & WQ_FLAG_WOKEN)) { |
| if (signal_pending_state(TASK_UNINTERRUPTIBLE, current)) |
| break; |
| |
| io_schedule(); |
| continue; |
| } |
| break; |
| } |
| |
| finish_wait(q, wait); |
| |
| if (thrashing) { |
| delayacct_thrashing_end(&in_thrashing); |
| psi_memstall_leave(&pflags); |
| } |
| } |
| #endif |
| |
| void folio_wait_bit(struct folio *folio, int bit_nr) |
| { |
| folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED); |
| } |
| EXPORT_SYMBOL(folio_wait_bit); |
| |
| int folio_wait_bit_killable(struct folio *folio, int bit_nr) |
| { |
| return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED); |
| } |
| EXPORT_SYMBOL(folio_wait_bit_killable); |
| |
| /** |
| * folio_put_wait_locked - Drop a reference and wait for it to be unlocked |
| * @folio: The folio to wait for. |
| * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc). |
| * |
| * The caller should hold a reference on @folio. They expect the page to |
| * become unlocked relatively soon, but do not wish to hold up migration |
| * (for example) by holding the reference while waiting for the folio to |
| * come unlocked. After this function returns, the caller should not |
| * dereference @folio. |
| * |
| * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal. |
| */ |
| static int folio_put_wait_locked(struct folio *folio, int state) |
| { |
| return folio_wait_bit_common(folio, PG_locked, state, DROP); |
| } |
| |
| /** |
| * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue |
| * @folio: Folio defining the wait queue of interest |
| * @waiter: Waiter to add to the queue |
| * |
| * Add an arbitrary @waiter to the wait queue for the nominated @folio. |
| */ |
| void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter) |
| { |
| wait_queue_head_t *q = folio_waitqueue(folio); |
| unsigned long flags; |
| |
| spin_lock_irqsave(&q->lock, flags); |
| __add_wait_queue_entry_tail(q, waiter); |
| folio_set_waiters(folio); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL_GPL(folio_add_wait_queue); |
| |
| #ifndef clear_bit_unlock_is_negative_byte |
| |
| /* |
| * PG_waiters is the high bit in the same byte as PG_lock. |
| * |
| * On x86 (and on many other architectures), we can clear PG_lock and |
| * test the sign bit at the same time. But if the architecture does |
| * not support that special operation, we just do this all by hand |
| * instead. |
| * |
| * The read of PG_waiters has to be after (or concurrently with) PG_locked |
| * being cleared, but a memory barrier should be unnecessary since it is |
| * in the same byte as PG_locked. |
| */ |
| static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) |
| { |
| clear_bit_unlock(nr, mem); |
| /* smp_mb__after_atomic(); */ |
| return test_bit(PG_waiters, mem); |
| } |
| |
| #endif |
| |
| /** |
| * folio_unlock - Unlock a locked folio. |
| * @folio: The folio. |
| * |
| * Unlocks the folio and wakes up any thread sleeping on the page lock. |
| * |
| * Context: May be called from interrupt or process context. May not be |
| * called from NMI context. |
| */ |
| void folio_unlock(struct folio *folio) |
| { |
| /* Bit 7 allows x86 to check the byte's sign bit */ |
| BUILD_BUG_ON(PG_waiters != 7); |
| BUILD_BUG_ON(PG_locked > 7); |
| VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0))) |
| folio_wake_bit(folio, PG_locked); |
| } |
| EXPORT_SYMBOL(folio_unlock); |
| |
| /** |
| * folio_end_private_2 - Clear PG_private_2 and wake any waiters. |
| * @folio: The folio. |
| * |
| * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for |
| * it. The folio reference held for PG_private_2 being set is released. |
| * |
| * This is, for example, used when a netfs folio is being written to a local |
| * disk cache, thereby allowing writes to the cache for the same folio to be |
| * serialised. |
| */ |
| void folio_end_private_2(struct folio *folio) |
| { |
| VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio); |
| clear_bit_unlock(PG_private_2, folio_flags(folio, 0)); |
| folio_wake_bit(folio, PG_private_2); |
| folio_put(folio); |
| } |
| EXPORT_SYMBOL(folio_end_private_2); |
| |
| /** |
| * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio. |
| * @folio: The folio to wait on. |
| * |
| * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio. |
| */ |
| void folio_wait_private_2(struct folio *folio) |
| { |
| while (folio_test_private_2(folio)) |
| folio_wait_bit(folio, PG_private_2); |
| } |
| EXPORT_SYMBOL(folio_wait_private_2); |
| |
| /** |
| * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio. |
| * @folio: The folio to wait on. |
| * |
| * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a |
| * fatal signal is received by the calling task. |
| * |
| * Return: |
| * - 0 if successful. |
| * - -EINTR if a fatal signal was encountered. |
| */ |
| int folio_wait_private_2_killable(struct folio *folio) |
| { |
| int ret = 0; |
| |
| while (folio_test_private_2(folio)) { |
| ret = folio_wait_bit_killable(folio, PG_private_2); |
| if (ret < 0) |
| break; |
| } |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(folio_wait_private_2_killable); |
| |
| /** |
| * folio_end_writeback - End writeback against a folio. |
| * @folio: The folio. |
| */ |
| void folio_end_writeback(struct folio *folio) |
| { |
| /* |
| * folio_test_clear_reclaim() could be used here but it is an |
| * atomic operation and overkill in this particular case. Failing |
| * to shuffle a folio marked for immediate reclaim is too mild |
| * a gain to justify taking an atomic operation penalty at the |
| * end of every folio writeback. |
| */ |
| if (folio_test_reclaim(folio)) { |
| folio_clear_reclaim(folio); |
| folio_rotate_reclaimable(folio); |
| } |
| |
| /* |
| * Writeback does not hold a folio reference of its own, relying |
| * on truncation to wait for the clearing of PG_writeback. |
| * But here we must make sure that the folio is not freed and |
| * reused before the folio_wake(). |
| */ |
| folio_get(folio); |
| if (!__folio_end_writeback(folio)) |
| BUG(); |
| |
| smp_mb__after_atomic(); |
| folio_wake(folio, PG_writeback); |
| acct_reclaim_writeback(folio); |
| folio_put(folio); |
| } |
| EXPORT_SYMBOL(folio_end_writeback); |
| |
| /* |
| * After completing I/O on a page, call this routine to update the page |
| * flags appropriately |
| */ |
| void page_endio(struct page *page, bool is_write, int err) |
| { |
| struct folio *folio = page_folio(page); |
| |
| if (!is_write) { |
| if (!err) { |
| folio_mark_uptodate(folio); |
| } else { |
| folio_clear_uptodate(folio); |
| folio_set_error(folio); |
| } |
| folio_unlock(folio); |
| } else { |
| if (err) { |
| struct address_space *mapping; |
| |
| folio_set_error(folio); |
| mapping = folio_mapping(folio); |
| if (mapping) |
| mapping_set_error(mapping, err); |
| } |
| folio_end_writeback(folio); |
| } |
| } |
| EXPORT_SYMBOL_GPL(page_endio); |
| |
| /** |
| * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it. |
| * @folio: The folio to lock |
| */ |
| void __folio_lock(struct folio *folio) |
| { |
| folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE, |
| EXCLUSIVE); |
| } |
| EXPORT_SYMBOL(__folio_lock); |
| |
| int __folio_lock_killable(struct folio *folio) |
| { |
| return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE, |
| EXCLUSIVE); |
| } |
| EXPORT_SYMBOL_GPL(__folio_lock_killable); |
| |
| static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait) |
| { |
| struct wait_queue_head *q = folio_waitqueue(folio); |
| int ret = 0; |
| |
| wait->folio = folio; |
| wait->bit_nr = PG_locked; |
| |
| spin_lock_irq(&q->lock); |
| __add_wait_queue_entry_tail(q, &wait->wait); |
| folio_set_waiters(folio); |
| ret = !folio_trylock(folio); |
| /* |
| * If we were successful now, we know we're still on the |
| * waitqueue as we're still under the lock. This means it's |
| * safe to remove and return success, we know the callback |
| * isn't going to trigger. |
| */ |
| if (!ret) |
| __remove_wait_queue(q, &wait->wait); |
| else |
| ret = -EIOCBQUEUED; |
| spin_unlock_irq(&q->lock); |
| return ret; |
| } |
| |
| /* |
| * Return values: |
| * true - folio is locked; mmap_lock is still held. |
| * false - folio is not locked. |
| * mmap_lock has been released (mmap_read_unlock(), unless flags had both |
| * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in |
| * which case mmap_lock is still held. |
| * |
| * If neither ALLOW_RETRY nor KILLABLE are set, will always return true |
| * with the folio locked and the mmap_lock unperturbed. |
| */ |
| bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm, |
| unsigned int flags) |
| { |
| if (fault_flag_allow_retry_first(flags)) { |
| /* |
| * CAUTION! In this case, mmap_lock is not released |
| * even though return 0. |
| */ |
| if (flags & FAULT_FLAG_RETRY_NOWAIT) |
| return false; |
| |
| mmap_read_unlock(mm); |
| if (flags & FAULT_FLAG_KILLABLE) |
| folio_wait_locked_killable(folio); |
| else |
| folio_wait_locked(folio); |
| return false; |
| } |
| if (flags & FAULT_FLAG_KILLABLE) { |
| bool ret; |
| |
| ret = __folio_lock_killable(folio); |
| if (ret) { |
| mmap_read_unlock(mm); |
| return false; |
| } |
| } else { |
| __folio_lock(folio); |
| } |
| |
| return true; |
| } |
| |
| /** |
| * page_cache_next_miss() - Find the next gap in the page cache. |
| * @mapping: Mapping. |
| * @index: Index. |
| * @max_scan: Maximum range to search. |
| * |
| * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the |
| * gap with the lowest index. |
| * |
| * This function may be called under the rcu_read_lock. However, this will |
| * not atomically search a snapshot of the cache at a single point in time. |
| * For example, if a gap is created at index 5, then subsequently a gap is |
| * created at index 10, page_cache_next_miss covering both indices may |
| * return 10 if called under the rcu_read_lock. |
| * |
| * Return: The index of the gap if found, otherwise an index outside the |
| * range specified (in which case 'return - index >= max_scan' will be true). |
| * In the rare case of index wrap-around, 0 will be returned. |
| */ |
| pgoff_t page_cache_next_miss(struct address_space *mapping, |
| pgoff_t index, unsigned long max_scan) |
| { |
| XA_STATE(xas, &mapping->i_pages, index); |
| |
| while (max_scan--) { |
| void *entry = xas_next(&xas); |
| if (!entry || xa_is_value(entry)) |
| break; |
| if (xas.xa_index == 0) |
| break; |
| } |
| |
| return xas.xa_index; |
| } |
| EXPORT_SYMBOL(page_cache_next_miss); |
| |
| /** |
| * page_cache_prev_miss() - Find the previous gap in the page cache. |
| * @mapping: Mapping. |
| * @index: Index. |
| * @max_scan: Maximum range to search. |
| * |
| * Search the range [max(index - max_scan + 1, 0), index] for the |
| * gap with the highest index. |
| * |
| * This function may be called under the rcu_read_lock. However, this will |
| * not atomically search a snapshot of the cache at a single point in time. |
| * For example, if a gap is created at index 10, then subsequently a gap is |
| * created at index 5, page_cache_prev_miss() covering both indices may |
| * return 5 if called under the rcu_read_lock. |
| * |
| * Return: The index of the gap if found, otherwise an index outside the |
| * range specified (in which case 'index - return >= max_scan' will be true). |
| * In the rare case of wrap-around, ULONG_MAX will be returned. |
| */ |
| pgoff_t page_cache_prev_miss(struct address_space *mapping, |
| pgoff_t index, unsigned long max_scan) |
| { |
| XA_STATE(xas, &mapping->i_pages, index); |
| |
| while (max_scan--) { |
| void *entry = xas_prev(&xas); |
| if (!entry || xa_is_value(entry)) |
| break; |
| if (xas.xa_index == ULONG_MAX) |
| break; |
| } |
| |
| return xas.xa_index; |
| } |
| EXPORT_SYMBOL(page_cache_prev_miss); |
| |
| /* |
| * Lockless page cache protocol: |
| * On the lookup side: |
| * 1. Load the folio from i_pages |
| * 2. Increment the refcount if it's not zero |
| * 3. If the folio is not found by xas_reload(), put the refcount and retry |
| * |
| * On the removal side: |
| * A. Freeze the page (by zeroing the refcount if nobody else has a reference) |
| * B. Remove the page from i_pages |
| * C. Return the page to the page allocator |
| * |
| * This means that any page may have its reference count temporarily |
| * increased by a speculative page cache (or fast GUP) lookup as it can |
| * be allocated by another user before the RCU grace period expires. |
| * Because the refcount temporarily acquired here may end up being the |
| * last refcount on the page, any page allocation must be freeable by |
| * folio_put(). |
| */ |
| |
| /* |
| * mapping_get_entry - Get a page cache entry. |
| * @mapping: the address_space to search |
| * @index: The page cache index. |
| * |
| * Looks up the page cache entry at @mapping & @index. If it is a folio, |
| * it is returned with an increased refcount. If it is a shadow entry |
| * of a previously evicted folio, or a swap entry from shmem/tmpfs, |
| * it is returned without further action. |
| * |
| * Return: The folio, swap or shadow entry, %NULL if nothing is found. |
| */ |
| static void *mapping_get_entry(struct address_space *mapping, pgoff_t index) |
| { |
| XA_STATE(xas, &mapping->i_pages, index); |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| repeat: |
| xas_reset(&xas); |
| folio = xas_load(&xas); |
| if (xas_retry(&xas, folio)) |
| goto repeat; |
| /* |
| * A shadow entry of a recently evicted page, or a swap entry from |
| * shmem/tmpfs. Return it without attempting to raise page count. |
| */ |
| if (!folio || xa_is_value(folio)) |
| goto out; |
| |
| if (!folio_try_get_rcu(folio)) |
| goto repeat; |
| |
| if (unlikely(folio != xas_reload(&xas))) { |
| folio_put(folio); |
| goto repeat; |
| } |
| out: |
| rcu_read_unlock(); |
| |
| return folio; |
| } |
| |
| /** |
| * __filemap_get_folio - Find and get a reference to a folio. |
| * @mapping: The address_space to search. |
| * @index: The page index. |
| * @fgp_flags: %FGP flags modify how the folio is returned. |
| * @gfp: Memory allocation flags to use if %FGP_CREAT is specified. |
| * |
| * Looks up the page cache entry at @mapping & @index. |
| * |
| * @fgp_flags can be zero or more of these flags: |
| * |
| * * %FGP_ACCESSED - The folio will be marked accessed. |
| * * %FGP_LOCK - The folio is returned locked. |
| * * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it |
| * instead of allocating a new folio to replace it. |
| * * %FGP_CREAT - If no page is present then a new page is allocated using |
| * @gfp and added to the page cache and the VM's LRU list. |
| * The page is returned locked and with an increased refcount. |
| * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the |
| * page is already in cache. If the page was allocated, unlock it before |
| * returning so the caller can do the same dance. |
| * * %FGP_WRITE - The page will be written to by the caller. |
| * * %FGP_NOFS - __GFP_FS will get cleared in gfp. |
| * * %FGP_NOWAIT - Don't get blocked by page lock. |
| * * %FGP_STABLE - Wait for the folio to be stable (finished writeback) |
| * |
| * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even |
| * if the %GFP flags specified for %FGP_CREAT are atomic. |
| * |
| * If there is a page cache page, it is returned with an increased refcount. |
| * |
| * Return: The found folio or %NULL otherwise. |
| */ |
| struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, |
| int fgp_flags, gfp_t gfp) |
| { |
| struct folio *folio; |
| |
| repeat: |
| folio = mapping_get_entry(mapping, index); |
| if (xa_is_value(folio)) { |
| if (fgp_flags & FGP_ENTRY) |
| return folio; |
| folio = NULL; |
| } |
| if (!folio) |
| goto no_page; |
| |
| if (fgp_flags & FGP_LOCK) { |
| if (fgp_flags & FGP_NOWAIT) { |
| if (!folio_trylock(folio)) { |
| folio_put(folio); |
| return NULL; |
| } |
| } else { |
| folio_lock(folio); |
| } |
| |
| /* Has the page been truncated? */ |
| if (unlikely(folio->mapping != mapping)) { |
| folio_unlock(folio); |
| folio_put(folio); |
| goto repeat; |
| } |
| VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); |
| } |
| |
| if (fgp_flags & FGP_ACCESSED) |
| folio_mark_accessed(folio); |
| else if (fgp_flags & FGP_WRITE) { |
| /* Clear idle flag for buffer write */ |
| if (folio_test_idle(folio)) |
| folio_clear_idle(folio); |
| } |
| |
| if (fgp_flags & FGP_STABLE) |
| folio_wait_stable(folio); |
| no_page: |
| if (!folio && (fgp_flags & FGP_CREAT)) { |
| int err; |
| if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping)) |
| gfp |= __GFP_WRITE; |
| if (fgp_flags & FGP_NOFS) |
| gfp &= ~__GFP_FS; |
| if (fgp_flags & FGP_NOWAIT) { |
| gfp &= ~GFP_KERNEL; |
| gfp |= GFP_NOWAIT | __GFP_NOWARN; |
| } |
| |
| folio = filemap_alloc_folio(gfp, 0); |
| if (!folio) |
| return NULL; |
| |
| if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) |
| fgp_flags |= FGP_LOCK; |
| |
| /* Init accessed so avoid atomic mark_page_accessed later */ |
| if (fgp_flags & FGP_ACCESSED) |
| __folio_set_referenced(folio); |
| |
| err = filemap_add_folio(mapping, folio, index, gfp); |
| if (unlikely(err)) { |
| folio_put(folio); |
| folio = NULL; |
| if (err == -EEXIST) |
| goto repeat; |
| } |
| |
| /* |
| * filemap_add_folio locks the page, and for mmap |
| * we expect an unlocked page. |
| */ |
| if (folio && (fgp_flags & FGP_FOR_MMAP)) |
| folio_unlock(folio); |
| } |
| |
| return folio; |
| } |
| EXPORT_SYMBOL(__filemap_get_folio); |
| |
| static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max, |
| xa_mark_t mark) |
| { |
| struct folio *folio; |
| |
| retry: |
| if (mark == XA_PRESENT) |
| folio = xas_find(xas, max); |
| else |
| folio = xas_find_marked(xas, max, mark); |
| |
| if (xas_retry(xas, folio)) |
| goto retry; |
| /* |
| * A shadow entry of a recently evicted page, a swap |
| * entry from shmem/tmpfs or a DAX entry. Return it |
| * without attempting to raise page count. |
| */ |
| if (!folio || xa_is_value(folio)) |
| return folio; |
| |
| if (!folio_try_get_rcu(folio)) |
| goto reset; |
| |
| if (unlikely(folio != xas_reload(xas))) { |
| folio_put(folio); |
| goto reset; |
| } |
| |
| return folio; |
| reset: |
| xas_reset(xas); |
| goto retry; |
| } |
| |
| /** |
| * find_get_entries - gang pagecache lookup |
| * @mapping: The address_space to search |
| * @start: The starting page cache index |
| * @end: The final page index (inclusive). |
| * @fbatch: Where the resulting entries are placed. |
| * @indices: The cache indices corresponding to the entries in @entries |
| * |
| * find_get_entries() will search for and return a batch of entries in |
| * the mapping. The entries are placed in @fbatch. find_get_entries() |
| * takes a reference on any actual folios it returns. |
| * |
| * The entries have ascending indexes. The indices may not be consecutive |
| * due to not-present entries or large folios. |
| * |
| * Any shadow entries of evicted folios, or swap entries from |
| * shmem/tmpfs, are included in the returned array. |
| * |
| * Return: The number of entries which were found. |
| */ |
| unsigned find_get_entries(struct address_space *mapping, pgoff_t start, |
| pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices) |
| { |
| XA_STATE(xas, &mapping->i_pages, start); |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) { |
| indices[fbatch->nr] = xas.xa_index; |
| if (!folio_batch_add(fbatch, folio)) |
| break; |
| } |
| rcu_read_unlock(); |
| |
| return folio_batch_count(fbatch); |
| } |
| |
| /** |
| * find_lock_entries - Find a batch of pagecache entries. |
| * @mapping: The address_space to search. |
| * @start: The starting page cache index. |
| * @end: The final page index (inclusive). |
| * @fbatch: Where the resulting entries are placed. |
| * @indices: The cache indices of the entries in @fbatch. |
| * |
| * find_lock_entries() will return a batch of entries from @mapping. |
| * Swap, shadow and DAX entries are included. Folios are returned |
| * locked and with an incremented refcount. Folios which are locked |
| * by somebody else or under writeback are skipped. Folios which are |
| * partially outside the range are not returned. |
| * |
| * The entries have ascending indexes. The indices may not be consecutive |
| * due to not-present entries, large folios, folios which could not be |
| * locked or folios under writeback. |
| * |
| * Return: The number of entries which were found. |
| */ |
| unsigned find_lock_entries(struct address_space *mapping, pgoff_t start, |
| pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices) |
| { |
| XA_STATE(xas, &mapping->i_pages, start); |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| while ((folio = find_get_entry(&xas, end, XA_PRESENT))) { |
| if (!xa_is_value(folio)) { |
| if (folio->index < start) |
| goto put; |
| if (folio->index + folio_nr_pages(folio) - 1 > end) |
| goto put; |
| if (!folio_trylock(folio)) |
| goto put; |
| if (folio->mapping != mapping || |
| folio_test_writeback(folio)) |
| goto unlock; |
| VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index), |
| folio); |
| } |
| indices[fbatch->nr] = xas.xa_index; |
| if (!folio_batch_add(fbatch, folio)) |
| break; |
| continue; |
| unlock: |
| folio_unlock(folio); |
| put: |
| folio_put(folio); |
| } |
| rcu_read_unlock(); |
| |
| return folio_batch_count(fbatch); |
| } |
| |
| /** |
| * filemap_get_folios - Get a batch of folios |
| * @mapping: The address_space to search |
| * @start: The starting page index |
| * @end: The final page index (inclusive) |
| * @fbatch: The batch to fill. |
| * |
| * Search for and return a batch of folios in the mapping starting at |
| * index @start and up to index @end (inclusive). The folios are returned |
| * in @fbatch with an elevated reference count. |
| * |
| * The first folio may start before @start; if it does, it will contain |
| * @start. The final folio may extend beyond @end; if it does, it will |
| * contain @end. The folios have ascending indices. There may be gaps |
| * between the folios if there are indices which have no folio in the |
| * page cache. If folios are added to or removed from the page cache |
| * while this is running, they may or may not be found by this call. |
| * |
| * Return: The number of folios which were found. |
| * We also update @start to index the next folio for the traversal. |
| */ |
| unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start, |
| pgoff_t end, struct folio_batch *fbatch) |
| { |
| XA_STATE(xas, &mapping->i_pages, *start); |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) { |
| /* Skip over shadow, swap and DAX entries */ |
| if (xa_is_value(folio)) |
| continue; |
| if (!folio_batch_add(fbatch, folio)) { |
| unsigned long nr = folio_nr_pages(folio); |
| |
| if (folio_test_hugetlb(folio)) |
| nr = 1; |
| *start = folio->index + nr; |
| goto out; |
| } |
| } |
| |
| /* |
| * We come here when there is no page beyond @end. We take care to not |
| * overflow the index @start as it confuses some of the callers. This |
| * breaks the iteration when there is a page at index -1 but that is |
| * already broken anyway. |
| */ |
| if (end == (pgoff_t)-1) |
| *start = (pgoff_t)-1; |
| else |
| *start = end + 1; |
| out: |
| rcu_read_unlock(); |
| |
| return folio_batch_count(fbatch); |
| } |
| EXPORT_SYMBOL(filemap_get_folios); |
| |
| static inline |
| bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max) |
| { |
| if (!folio_test_large(folio) || folio_test_hugetlb(folio)) |
| return false; |
| if (index >= max) |
| return false; |
| return index < folio->index + folio_nr_pages(folio) - 1; |
| } |
| |
| /** |
| * filemap_get_folios_contig - Get a batch of contiguous folios |
| * @mapping: The address_space to search |
| * @start: The starting page index |
| * @end: The final page index (inclusive) |
| * @fbatch: The batch to fill |
| * |
| * filemap_get_folios_contig() works exactly like filemap_get_folios(), |
| * except the returned folios are guaranteed to be contiguous. This may |
| * not return all contiguous folios if the batch gets filled up. |
| * |
| * Return: The number of folios found. |
| * Also update @start to be positioned for traversal of the next folio. |
| */ |
| |
| unsigned filemap_get_folios_contig(struct address_space *mapping, |
| pgoff_t *start, pgoff_t end, struct folio_batch *fbatch) |
| { |
| XA_STATE(xas, &mapping->i_pages, *start); |
| unsigned long nr; |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| |
| for (folio = xas_load(&xas); folio && xas.xa_index <= end; |
| folio = xas_next(&xas)) { |
| if (xas_retry(&xas, folio)) |
| continue; |
| /* |
| * If the entry has been swapped out, we can stop looking. |
| * No current caller is looking for DAX entries. |
| */ |
| if (xa_is_value(folio)) |
| goto update_start; |
| |
| if (!folio_try_get_rcu(folio)) |
| goto retry; |
| |
| if (unlikely(folio != xas_reload(&xas))) |
| goto put_folio; |
| |
| if (!folio_batch_add(fbatch, folio)) { |
| nr = folio_nr_pages(folio); |
| |
| if (folio_test_hugetlb(folio)) |
| nr = 1; |
| *start = folio->index + nr; |
| goto out; |
| } |
| continue; |
| put_folio: |
| folio_put(folio); |
| |
| retry: |
| xas_reset(&xas); |
| } |
| |
| update_start: |
| nr = folio_batch_count(fbatch); |
| |
| if (nr) { |
| folio = fbatch->folios[nr - 1]; |
| if (folio_test_hugetlb(folio)) |
| *start = folio->index + 1; |
| else |
| *start = folio->index + folio_nr_pages(folio); |
| } |
| out: |
| rcu_read_unlock(); |
| return folio_batch_count(fbatch); |
| } |
| EXPORT_SYMBOL(filemap_get_folios_contig); |
| |
| /** |
| * find_get_pages_range_tag - Find and return head pages matching @tag. |
| * @mapping: the address_space to search |
| * @index: the starting page index |
| * @end: The final page index (inclusive) |
| * @tag: the tag index |
| * @nr_pages: the maximum number of pages |
| * @pages: where the resulting pages are placed |
| * |
| * Like find_get_pages_range(), except we only return head pages which are |
| * tagged with @tag. @index is updated to the index immediately after the |
| * last page we return, ready for the next iteration. |
| * |
| * Return: the number of pages which were found. |
| */ |
| unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, |
| pgoff_t end, xa_mark_t tag, unsigned int nr_pages, |
| struct page **pages) |
| { |
| XA_STATE(xas, &mapping->i_pages, *index); |
| struct folio *folio; |
| unsigned ret = 0; |
| |
| if (unlikely(!nr_pages)) |
| return 0; |
| |
| rcu_read_lock(); |
| while ((folio = find_get_entry(&xas, end, tag))) { |
| /* |
| * Shadow entries should never be tagged, but this iteration |
| * is lockless so there is a window for page reclaim to evict |
| * a page we saw tagged. Skip over it. |
| */ |
| if (xa_is_value(folio)) |
| continue; |
| |
| pages[ret] = &folio->page; |
| if (++ret == nr_pages) { |
| *index = folio->index + folio_nr_pages(folio); |
| goto out; |
| } |
| } |
| |
| /* |
| * We come here when we got to @end. We take care to not overflow the |
| * index @index as it confuses some of the callers. This breaks the |
| * iteration when there is a page at index -1 but that is already |
| * broken anyway. |
| */ |
| if (end == (pgoff_t)-1) |
| *index = (pgoff_t)-1; |
| else |
| *index = end + 1; |
| out: |
| rcu_read_unlock(); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(find_get_pages_range_tag); |
| |
| /* |
| * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
| * a _large_ part of the i/o request. Imagine the worst scenario: |
| * |
| * ---R__________________________________________B__________ |
| * ^ reading here ^ bad block(assume 4k) |
| * |
| * read(R) => miss => readahead(R...B) => media error => frustrating retries |
| * => failing the whole request => read(R) => read(R+1) => |
| * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
| * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
| * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
| * |
| * It is going insane. Fix it by quickly scaling down the readahead size. |
| */ |
| static void shrink_readahead_size_eio(struct file_ra_state *ra) |
| { |
| ra->ra_pages /= 4; |
| } |
| |
| /* |
| * filemap_get_read_batch - Get a batch of folios for read |
| * |
| * Get a batch of folios which represent a contiguous range of bytes in |
| * the file. No exceptional entries will be returned. If @index is in |
| * the middle of a folio, the entire folio will be returned. The last |
| * folio in the batch may have the readahead flag set or the uptodate flag |
| * clear so that the caller can take the appropriate action. |
| */ |
| static void filemap_get_read_batch(struct address_space *mapping, |
| pgoff_t index, pgoff_t max, struct folio_batch *fbatch) |
| { |
| XA_STATE(xas, &mapping->i_pages, index); |
| struct folio *folio; |
| |
| rcu_read_lock(); |
| for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) { |
| if (xas_retry(&xas, folio)) |
| continue; |
| if (xas.xa_index > max || xa_is_value(folio)) |
| break; |
| if (xa_is_sibling(folio)) |
| break; |
| if (!folio_try_get_rcu(folio)) |
| goto retry; |
| |
| if (unlikely(folio != xas_reload(&xas))) |
| goto put_folio; |
| |
| if (!folio_batch_add(fbatch, folio)) |
| break; |
| if (!folio_test_uptodate(folio)) |
| break; |
| if (folio_test_readahead(folio)) |
| break; |
| xas_advance(&xas, folio->index + folio_nr_pages(folio) - 1); |
| continue; |
| put_folio: |
| folio_put(folio); |
| retry: |
| xas_reset(&xas); |
| } |
| rcu_read_unlock(); |
| } |
| |
| static int filemap_read_folio(struct file *file, filler_t filler, |
| struct folio *folio) |
| { |
| bool workingset = folio_test_workingset(folio); |
| unsigned long pflags; |
| int error; |
| |
| /* |
| * A previous I/O error may have been due to temporary failures, |
| * eg. multipath errors. PG_error will be set again if read_folio |
| * fails. |
| */ |
| folio_clear_error(folio); |
| |
| /* Start the actual read. The read will unlock the page. */ |
| if (unlikely(workingset)) |
| psi_memstall_enter(&pflags); |
| error = filler(file, folio); |
| if (unlikely(workingset)) |
| psi_memstall_leave(&pflags); |
| if (error) |
| return error; |
| |
| error = folio_wait_locked_killable(folio); |
| if (error) |
| return error; |
| if (folio_test_uptodate(folio)) |
| return 0; |
| if (file) |
| shrink_readahead_size_eio(&file->f_ra); |
| return -EIO; |
| } |
| |
| static bool filemap_range_uptodate(struct address_space *mapping, |
| loff_t pos, struct iov_iter *iter, struct folio *folio) |
| { |
| int count; |
| |
| if (folio_test_uptodate(folio)) |
| return true; |
| /* pipes can't handle partially uptodate pages */ |
| if (iov_iter_is_pipe(iter)) |
| return false; |
| if (!mapping->a_ops->is_partially_uptodate) |
| return false; |
| if (mapping->host->i_blkbits >= folio_shift(folio)) |
| return false; |
| |
| count = iter->count; |
| if (folio_pos(folio) > pos) { |
| count -= folio_pos(folio) - pos; |
| pos = 0; |
| } else { |
| pos -= folio_pos(folio); |
| } |
| |
| return mapping->a_ops->is_partially_uptodate(folio, pos, count); |
| } |
| |
| static int filemap_update_page(struct kiocb *iocb, |
| struct address_space *mapping, struct iov_iter *iter, |
| struct folio *folio) |
| { |
| int error; |
| |
| if (iocb->ki_flags & IOCB_NOWAIT) { |
| if (!filemap_invalidate_trylock_shared(mapping)) |
| return -EAGAIN; |
| } else { |
| filemap_invalidate_lock_shared(mapping); |
| } |
| |
| if (!folio_trylock(folio)) { |
| error = -EAGAIN; |
| if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) |
| goto unlock_mapping; |
| if (!(iocb->ki_flags & IOCB_WAITQ)) { |
| filemap_invalidate_unlock_shared(mapping); |
| /* |
| * This is where we usually end up waiting for a |
| * previously submitted readahead to finish. |
| */ |
| folio_put_wait_locked(folio, TASK_KILLABLE); |
| return AOP_TRUNCATED_PAGE; |
| } |
| error = __folio_lock_async(folio, iocb->ki_waitq); |
| if (error) |
| goto unlock_mapping; |
| } |
| |
| error = AOP_TRUNCATED_PAGE; |
| if (!folio->mapping) |
| goto unlock; |
| |
| error = 0; |
| if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, folio)) |
| goto unlock; |
| |
| error = -EAGAIN; |
| if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) |
| goto unlock; |
| |
| error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio, |
| folio); |
| goto unlock_mapping; |
| unlock: |
| folio_unlock(folio); |
| unlock_mapping: |
| filemap_invalidate_unlock_shared(mapping); |
| if (error == AOP_TRUNCATED_PAGE) |
| folio_put(folio); |
| return error; |
| } |
| |
| static int filemap_create_folio(struct file *file, |
| struct address_space *mapping, pgoff_t index, |
| struct folio_batch *fbatch) |
| { |
| struct folio *folio; |
| int error; |
| |
| folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0); |
| if (!folio) |
| return -ENOMEM; |
| |
| /* |
| * Protect against truncate / hole punch. Grabbing invalidate_lock |
| * here assures we cannot instantiate and bring uptodate new |
| * pagecache folios after evicting page cache during truncate |
| * and before actually freeing blocks. Note that we could |
| * release invalidate_lock after inserting the folio into |
| * the page cache as the locked folio would then be enough to |
| * synchronize with hole punching. But there are code paths |
| * such as filemap_update_page() filling in partially uptodate |
| * pages or ->readahead() that need to hold invalidate_lock |
| * while mapping blocks for IO so let's hold the lock here as |
| * well to keep locking rules simple. |
| */ |
| filemap_invalidate_lock_shared(mapping); |
| error = filemap_add_folio(mapping, folio, index, |
| mapping_gfp_constraint(mapping, GFP_KERNEL)); |
| if (error == -EEXIST) |
| error = AOP_TRUNCATED_PAGE; |
| if (error) |
| goto error; |
| |
| error = filemap_read_folio(file, mapping->a_ops->read_folio, folio); |
| if (error) |
| goto error; |
| |
| filemap_invalidate_unlock_shared(mapping); |
| folio_batch_add(fbatch, folio); |
| return 0; |
| error: |
| filemap_invalidate_unlock_shared(mapping); |
| folio_put(folio); |
| return error; |
| } |
| |
| static int filemap_readahead(struct kiocb *iocb, struct file *file, |
| struct address_space *mapping, struct folio *folio, |
| pgoff_t last_index) |
| { |
| DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index); |
| |
| if (iocb->ki_flags & IOCB_NOIO) |
| return -EAGAIN; |
| page_cache_async_ra(&ractl, folio, last_index - folio->index); |
| return 0; |
| } |
| |
| static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter, |
| struct folio_batch *fbatch) |
| { |
| struct file *filp = iocb->ki_filp; |
| struct address_space *mapping = filp->f_mapping; |
| struct file_ra_state *ra = &filp->f_ra; |
| pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; |
| pgoff_t last_index; |
| struct folio *folio; |
| int err = 0; |
| |
| /* "last_index" is the index of the page beyond the end of the read */ |
| last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE); |
| retry: |
| if (fatal_signal_pending(current)) |
| return -EINTR; |
| |
| filemap_get_read_batch(mapping, index, last_index - 1, fbatch); |
| if (!folio_batch_count(fbatch)) { |
| if (iocb->ki_flags & IOCB_NOIO) |
| return -EAGAIN; |
| page_cache_sync_readahead(mapping, ra, filp, index, |
| last_index - index); |
| filemap_get_read_batch(mapping, index, last_index - 1, fbatch); |
| } |
| if (!folio_batch_count(fbatch)) { |
| if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) |
| return -EAGAIN; |
| err = filemap_create_folio(filp, mapping, |
| iocb->ki_pos >> PAGE_SHIFT, fbatch); |
| if (err == AOP_TRUNCATED_PAGE) |
| goto retry; |
| return err; |
| } |
| |
| folio = fbatch->folios[folio_batch_count(fbatch) - 1]; |
| if (folio_test_readahead(folio)) { |
| err = filemap_readahead(iocb, filp, mapping, folio, last_index); |
| if (err) |
| goto err; |
| } |
| if (!folio_test_uptodate(folio)) { |
| if ((iocb->ki_flags & IOCB_WAITQ) && |
| folio_batch_count(fbatch) > 1) |
| iocb->ki_flags |= IOCB_NOWAIT; |
| err = filemap_update_page(iocb, mapping, iter, folio); |
| if (err) |
| goto err; |
| } |
| |
| return 0; |
| err: |
| if (err < 0) |
| folio_put(folio); |
| if (likely(--fbatch->nr)) |
| return 0; |
| if (err == AOP_TRUNCATED_PAGE) |
| goto retry; |
| return err; |
| } |
| |
| static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio) |
| { |
| unsigned int shift = folio_shift(folio); |
| |
| return (pos1 >> shift == pos2 >> shift); |
| } |
| |
| /** |
| * filemap_read - Read data from the page cache. |
| * @iocb: The iocb to read. |
| * @iter: Destination for the data. |
| * @already_read: Number of bytes already read by the caller. |
| * |
| * Copies data from the page cache. If the data is not currently present, |
| * uses the readahead and read_folio address_space operations to fetch it. |
| * |
| * Return: Total number of bytes copied, including those already read by |
| * the caller. If an error happens before any bytes are copied, returns |
| * a negative error number. |
| */ |
| ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, |
| ssize_t already_read) |
| { |
| struct file *filp = iocb->ki_filp; |
| struct file_ra_state *ra = &filp->f_ra; |
| struct address_space *mapping = filp->f_mapping; |
| struct inode *inode = mapping->host; |
| struct folio_batch fbatch; |
| int i, error = 0; |
| bool writably_mapped; |
| loff_t isize, end_offset; |
| |
| if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes)) |
| return 0; |
| if (unlikely(!iov_iter_count(iter))) |
| return 0; |
| |
| iov_iter_truncate(iter, inode->i_sb->s_maxbytes); |
| folio_batch_init(&fbatch); |
| |
| do { |
| cond_resched(); |
| |
| /* |
| * If we've already successfully copied some data, then we |
| * can no longer safely return -EIOCBQUEUED. Hence mark |
| * an async read NOWAIT at that point. |
| */ |
| if ((iocb->ki_flags & IOCB_WAITQ) && already_read) |
| iocb->ki_flags |= IOCB_NOWAIT; |
| |
| if (unlikely(iocb->ki_pos >= i_size_read(inode))) |
| break; |
| |
| error = filemap_get_pages(iocb, iter, &fbatch); |
| if (error < 0) |
| break; |
| |
| /* |
| * i_size must be checked after we know the pages are Uptodate. |
| * |
| * Checking i_size after the check allows us to calculate |
| * the correct value for "nr", which means the zero-filled |
| * part of the page is not copied back to userspace (unless |
| * another truncate extends the file - this is desired though). |
| */ |
| isize = i_size_read(inode); |
| if (unlikely(iocb->ki_pos >= isize)) |
| goto put_folios; |
| end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count); |
| |
| /* |
| * Once we start copying data, we don't want to be touching any |
| * cachelines that might be contended: |
| */ |
| writably_mapped = mapping_writably_mapped(mapping); |
| |
| /* |
| * When a read accesses the same folio several times, only |
| * mark it as accessed the first time. |
| */ |
| if (!pos_same_folio(iocb->ki_pos, ra->prev_pos - 1, |
| fbatch.folios[0])) |
| folio_mark_accessed(fbatch.folios[0]); |
| |
| for (i = 0; i < folio_batch_count(&fbatch); i++) { |
| struct folio *folio = fbatch.folios[i]; |
| size_t fsize = folio_size(folio); |
| size_t offset = iocb->ki_pos & (fsize - 1); |
| size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos, |
| fsize - offset); |
| size_t copied; |
| |
| if (end_offset < folio_pos(folio)) |
| break; |
| if (i > 0) |
| folio_mark_accessed(folio); |
| /* |
| * If users can be writing to this folio using arbitrary |
| * virtual addresses, take care of potential aliasing |
| * before reading the folio on the kernel side. |
| */ |
| if (writably_mapped) |
| flush_dcache_folio(folio); |
| |
| copied = copy_folio_to_iter(folio, offset, bytes, iter); |
| |
| already_read += copied; |
| iocb->ki_pos += copied; |
| ra->prev_pos = iocb->ki_pos; |
| |
| if (copied < bytes) { |
| error = -EFAULT; |
| break; |
| } |
| } |
| put_folios: |
| for (i = 0; i < folio_batch_count(&fbatch); i++) |
| folio_put(fbatch.folios[i]); |
| folio_batch_init(&fbatch); |
| } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error); |
| |
| file_accessed(filp); |
| |
| return already_read ? already_read : error; |
| } |
| EXPORT_SYMBOL_GPL(filemap_read); |
| |
| /** |
| * generic_file_read_iter - generic filesystem read routine |
| * @iocb: kernel I/O control block |
| * @iter: destination for the data read |
| * |
| * This is the "read_iter()" routine for all filesystems |
| * that can use the page cache directly. |
| * |
| * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall |
| * be returned when no data can be read without waiting for I/O requests |
| * to complete; it doesn't prevent readahead. |
| * |
| * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O |
| * requests shall be made for the read or for readahead. When no data |
| * can be read, -EAGAIN shall be returned. When readahead would be |
| * triggered, a partial, possibly empty read shall be returned. |
| * |
| * Return: |
| * * number of bytes copied, even for partial reads |
| * * negative error code (or 0 if IOCB_NOIO) if nothing was read |
| */ |
| ssize_t |
| generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
| { |
| size_t count = iov_iter_count(iter); |
| ssize_t retval = 0; |
| |
| if (!count) |
| return 0; /* skip atime */ |
| |
| if (iocb->ki_flags & IOCB_DIRECT) { |
| struct file *file = iocb->ki_filp; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| |
| if (iocb->ki_flags & IOCB_NOWAIT) { |
| if (filemap_range_needs_writeback(mapping, iocb->ki_pos, |
| iocb->ki_pos + count - 1)) |
| return -EAGAIN; |
| } else { |
| retval = filemap_write_and_wait_range(mapping, |
| iocb->ki_pos, |
| iocb->ki_pos + count - 1); |
| if (retval < 0) |
| return retval; |
| } |
| |
| file_accessed(file); |
| |
| retval = mapping->a_ops->direct_IO(iocb, iter); |
| if (retval >= 0) { |
| iocb->ki_pos += retval; |
| count -= retval; |
| } |
| if (retval != -EIOCBQUEUED) |
| iov_iter_revert(iter, count - iov_iter_count(iter)); |
| |
| /* |
| * Btrfs can have a short DIO read if we encounter |
| * compressed extents, so if there was an error, or if |
| * we've already read everything we wanted to, or if |
| * there was a short read because we hit EOF, go ahead |
| * and return. Otherwise fallthrough to buffered io for |
| * the rest of the read. Buffered reads will not work for |
| * DAX files, so don't bother trying. |
| */ |
| if (retval < 0 || !count || IS_DAX(inode)) |
| return retval; |
| if (iocb->ki_pos >= i_size_read(inode)) |
| return retval; |
| } |
| |
| return filemap_read(iocb, iter, retval); |
| } |
| EXPORT_SYMBOL(generic_file_read_iter); |
| |
| static inline loff_t folio_seek_hole_data(struct xa_state *xas, |
| struct address_space *mapping, struct folio *folio, |
| loff_t start, loff_t end, bool seek_data) |
| { |
| const struct address_space_operations *ops = mapping->a_ops; |
| size_t offset, bsz = i_blocksize(mapping->host); |
| |
| if (xa_is_value(folio) || folio_test_uptodate(folio)) |
| return seek_data ? start : end; |
| if (!ops->is_partially_uptodate) |
| return seek_data ? end : start; |
| |
| xas_pause(xas); |
| rcu_read_unlock(); |
| folio_lock(folio); |
| if (unlikely(folio->mapping != mapping)) |
| goto unlock; |
| |
| offset = offset_in_folio(folio, start) & ~(bsz - 1); |
| |
| do { |
| if (ops->is_partially_uptodate(folio, offset, bsz) == |
| seek_data) |
| break; |
| start = (start + bsz) & ~(bsz - 1); |
| offset += bsz; |
| } while (offset < folio_size(folio)); |
| unlock: |
| folio_unlock(folio); |
| rcu_read_lock(); |
| return start; |
| } |
| |
| static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio) |
| { |
| if (xa_is_value(folio)) |
| return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index); |
| return folio_size(folio); |
| } |
| |
| /** |
| * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache. |
| * @mapping: Address space to search. |
| * @start: First byte to consider. |
| * @end: Limit of search (exclusive). |
| * @whence: Either SEEK_HOLE or SEEK_DATA. |
| * |
| * If the page cache knows which blocks contain holes and which blocks |
| * contain data, your filesystem can use this function to implement |
| * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are |
| * entirely memory-based such as tmpfs, and filesystems which support |
| * unwritten extents. |
| * |
| * Return: The requested offset on success, or -ENXIO if @whence specifies |
| * SEEK_DATA and there is no data after @start. There is an implicit hole |
| * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start |
| * and @end contain data. |
| */ |
| loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, |
| loff_t end, int whence) |
| { |
| XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); |
| pgoff_t max = (end - 1) >> PAGE_SHIFT; |
| bool seek_data = (whence == SEEK_DATA); |
| struct folio *folio; |
| |
| if (end <= start) |
| return -ENXIO; |
| |
| rcu_read_lock(); |
| while ((folio = find_get_entry(&xas, max, XA_PRESENT))) { |
| loff_t pos = (u64)xas.xa_index << PAGE_SHIFT; |
| size_t seek_size; |
| |
| if (start < pos) { |
| if (!seek_data) |
| goto unlock; |
| start = pos; |
| } |
| |
| seek_size = seek_folio_size(&xas, folio); |
| pos = round_up((u64)pos + 1, seek_size); |
| start = folio_seek_hole_data(&xas, mapping, folio, start, pos, |
| seek_data); |
| if (start < pos) |
| goto unlock; |
| if (start >= end) |
| break; |
| if (seek_size > PAGE_SIZE) |
| xas_set(&xas, pos >> PAGE_SHIFT); |
| if (!xa_is_value(folio)) |
| folio_put(folio); |
| } |
| if (seek_data) |
| start = -ENXIO; |
| unlock: |
| rcu_read_unlock(); |
| if (folio && !xa_is_value(folio)) |
| folio_put(folio); |
| if (start > end) |
| return end; |
| return start; |
| } |
| |
| #ifdef CONFIG_MMU |
| #define MMAP_LOTSAMISS (100) |
| /* |
| * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock |
| * @vmf - the vm_fault for this fault. |
| * @folio - the folio to lock. |
| * @fpin - the pointer to the file we may pin (or is already pinned). |
| * |
| * This works similar to lock_folio_or_retry in that it can drop the |
| * mmap_lock. It differs in that it actually returns the folio locked |
| * if it returns 1 and 0 if it couldn't lock the folio. If we did have |
| * to drop the mmap_lock then fpin will point to the pinned file and |
| * needs to be fput()'ed at a later point. |
| */ |
| static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio, |
| struct file **fpin) |
| { |
| if (folio_trylock(folio)) |
| return 1; |
| |
| /* |
| * NOTE! This will make us return with VM_FAULT_RETRY, but with |
| * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT |
| * is supposed to work. We have way too many special cases.. |
| */ |
| if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
| return 0; |
| |
| *fpin = maybe_unlock_mmap_for_io(vmf, *fpin); |
| if (vmf->flags & FAULT_FLAG_KILLABLE) { |
| if (__folio_lock_killable(folio)) { |
| /* |
| * We didn't have the right flags to drop the mmap_lock, |
| * but all fault_handlers only check for fatal signals |
| * if we return VM_FAULT_RETRY, so we need to drop the |
| * mmap_lock here and return 0 if we don't have a fpin. |
| */ |
| if (*fpin == NULL) |
| mmap_read_unlock(vmf->vma->vm_mm); |
| return 0; |
| } |
| } else |
| __folio_lock(folio); |
| |
| return 1; |
| } |
| |
| /* |
| * Synchronous readahead happens when we don't even find a page in the page |
| * cache at all. We don't want to perform IO under the mmap sem, so if we have |
| * to drop the mmap sem we return the file that was pinned in order for us to do |
| * that. If we didn't pin a file then we return NULL. The file that is |
| * returned needs to be fput()'ed when we're done with it. |
| */ |
| static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) |
| { |
| struct file *file = vmf->vma->vm_file; |
| struct file_ra_state *ra = &file->f_ra; |
| struct address_space *mapping = file->f_mapping; |
| DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff); |
| struct file *fpin = NULL; |
| unsigned long vm_flags = vmf->vma->vm_flags; |
| unsigned int mmap_miss; |
| |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| /* Use the readahead code, even if readahead is disabled */ |
| if (vm_flags & VM_HUGEPAGE) { |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1); |
| ra->size = HPAGE_PMD_NR; |
| /* |
| * Fetch two PMD folios, so we get the chance to actually |
| * readahead, unless we've been told not to. |
| */ |
| if (!(vm_flags & VM_RAND_READ)) |
| ra->size *= 2; |
| ra->async_size = HPAGE_PMD_NR; |
| page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER); |
| return fpin; |
| } |
| #endif |
| |
| /* If we don't want any read-ahead, don't bother */ |
| if (vm_flags & VM_RAND_READ) |
| return fpin; |
| if (!ra->ra_pages) |
| return fpin; |
| |
| if (vm_flags & VM_SEQ_READ) { |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| page_cache_sync_ra(&ractl, ra->ra_pages); |
| return fpin; |
| } |
| |
| /* Avoid banging the cache line if not needed */ |
| mmap_miss = READ_ONCE(ra->mmap_miss); |
| if (mmap_miss < MMAP_LOTSAMISS * 10) |
| WRITE_ONCE(ra->mmap_miss, ++mmap_miss); |
| |
| /* |
| * Do we miss much more than hit in this file? If so, |
| * stop bothering with read-ahead. It will only hurt. |
| */ |
| if (mmap_miss > MMAP_LOTSAMISS) |
| return fpin; |
| |
| /* |
| * mmap read-around |
| */ |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); |
| ra->size = ra->ra_pages; |
| ra->async_size = ra->ra_pages / 4; |
| ractl._index = ra->start; |
| page_cache_ra_order(&ractl, ra, 0); |
| return fpin; |
| } |
| |
| /* |
| * Asynchronous readahead happens when we find the page and PG_readahead, |
| * so we want to possibly extend the readahead further. We return the file that |
| * was pinned if we have to drop the mmap_lock in order to do IO. |
| */ |
| static struct file *do_async_mmap_readahead(struct vm_fault *vmf, |
| struct folio *folio) |
| { |
| struct file *file = vmf->vma->vm_file; |
| struct file_ra_state *ra = &file->f_ra; |
| DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff); |
| struct file *fpin = NULL; |
| unsigned int mmap_miss; |
| |
| /* If we don't want any read-ahead, don't bother */ |
| if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) |
| return fpin; |
| |
| mmap_miss = READ_ONCE(ra->mmap_miss); |
| if (mmap_miss) |
| WRITE_ONCE(ra->mmap_miss, --mmap_miss); |
| |
| if (folio_test_readahead(folio)) { |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| page_cache_async_ra(&ractl, folio, ra->ra_pages); |
| } |
| return fpin; |
| } |
| |
| /** |
| * filemap_fault - read in file data for page fault handling |
| * @vmf: struct vm_fault containing details of the fault |
| * |
| * filemap_fault() is invoked via the vma operations vector for a |
| * mapped memory region to read in file data during a page fault. |
| * |
| * The goto's are kind of ugly, but this streamlines the normal case of having |
| * it in the page cache, and handles the special cases reasonably without |
| * having a lot of duplicated code. |
| * |
| * vma->vm_mm->mmap_lock must be held on entry. |
| * |
| * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock |
| * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap(). |
| * |
| * If our return value does not have VM_FAULT_RETRY set, the mmap_lock |
| * has not been released. |
| * |
| * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. |
| * |
| * Return: bitwise-OR of %VM_FAULT_ codes. |
| */ |
| vm_fault_t filemap_fault(struct vm_fault *vmf) |
| { |
| int error; |
| struct file *file = vmf->vma->vm_file; |
| struct file *fpin = NULL; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| pgoff_t max_idx, index = vmf->pgoff; |
| struct folio *folio; |
| vm_fault_t ret = 0; |
| bool mapping_locked = false; |
| |
| max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| if (unlikely(index >= max_idx)) |
| return VM_FAULT_SIGBUS; |
| |
| /* |
| * Do we have something in the page cache already? |
| */ |
| folio = filemap_get_folio(mapping, index); |
| if (likely(folio)) { |
| /* |
| * We found the page, so try async readahead before waiting for |
| * the lock. |
| */ |
| if (!(vmf->flags & FAULT_FLAG_TRIED)) |
| fpin = do_async_mmap_readahead(vmf, folio); |
| if (unlikely(!folio_test_uptodate(folio))) { |
| filemap_invalidate_lock_shared(mapping); |
| mapping_locked = true; |
| } |
| } else { |
| /* No page in the page cache at all */ |
| count_vm_event(PGMAJFAULT); |
| count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); |
| ret = VM_FAULT_MAJOR; |
| fpin = do_sync_mmap_readahead(vmf); |
| retry_find: |
| /* |
| * See comment in filemap_create_folio() why we need |
| * invalidate_lock |
| */ |
| if (!mapping_locked) { |
| filemap_invalidate_lock_shared(mapping); |
| mapping_locked = true; |
| } |
| folio = __filemap_get_folio(mapping, index, |
| FGP_CREAT|FGP_FOR_MMAP, |
| vmf->gfp_mask); |
| if (!folio) { |
| if (fpin) |
| goto out_retry; |
| filemap_invalidate_unlock_shared(mapping); |
| return VM_FAULT_OOM; |
| } |
| } |
| |
| if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin)) |
| goto out_retry; |
| |
| /* Did it get truncated? */ |
| if (unlikely(folio->mapping != mapping)) { |
| folio_unlock(folio); |
| folio_put(folio); |
| goto retry_find; |
| } |
| VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); |
| |
| /* |
| * We have a locked page in the page cache, now we need to check |
| * that it's up-to-date. If not, it is going to be due to an error. |
| */ |
| if (unlikely(!folio_test_uptodate(folio))) { |
| /* |
| * The page was in cache and uptodate and now it is not. |
| * Strange but possible since we didn't hold the page lock all |
| * the time. Let's drop everything get the invalidate lock and |
| * try again. |
| */ |
| if (!mapping_locked) { |
| folio_unlock(folio); |
| folio_put(folio); |
| goto retry_find; |
| } |
| goto page_not_uptodate; |
| } |
| |
| /* |
| * We've made it this far and we had to drop our mmap_lock, now is the |
| * time to return to the upper layer and have it re-find the vma and |
| * redo the fault. |
| */ |
| if (fpin) { |
| folio_unlock(folio); |
| goto out_retry; |
| } |
| if (mapping_locked) |
| filemap_invalidate_unlock_shared(mapping); |
| |
| /* |
| * Found the page and have a reference on it. |
| * We must recheck i_size under page lock. |
| */ |
| max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| if (unlikely(index >= max_idx)) { |
| folio_unlock(folio); |
| folio_put(folio); |
| return VM_FAULT_SIGBUS; |
| } |
| |
| vmf->page = folio_file_page(folio, index); |
| return ret | VM_FAULT_LOCKED; |
| |
| page_not_uptodate: |
| /* |
| * Umm, take care of errors if the page isn't up-to-date. |
| * Try to re-read it _once_. We do this synchronously, |
| * because there really aren't any performance issues here |
| * and we need to check for errors. |
| */ |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| error = filemap_read_folio(file, mapping->a_ops->read_folio, folio); |
| if (fpin) |
| goto out_retry; |
| folio_put(folio); |
| |
| if (!error || error == AOP_TRUNCATED_PAGE) |
| goto retry_find; |
| filemap_invalidate_unlock_shared(mapping); |
| |
| return VM_FAULT_SIGBUS; |
| |
| out_retry: |
| /* |
| * We dropped the mmap_lock, we need to return to the fault handler to |
| * re-find the vma and come back and find our hopefully still populated |
| * page. |
| */ |
| if (folio) |
| folio_put(folio); |
| if (mapping_locked) |
| filemap_invalidate_unlock_shared(mapping); |
| if (fpin) |
| fput(fpin); |
| return ret | VM_FAULT_RETRY; |
| } |
| EXPORT_SYMBOL(filemap_fault); |
| |
| static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) |
| { |
| struct mm_struct *mm = vmf->vma->vm_mm; |
| |
| /* Huge page is mapped? No need to proceed. */ |
| if (pmd_trans_huge(*vmf->pmd)) { |
| unlock_page(page); |
| put_page(page); |
| return true; |
| } |
| |
| if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { |
| vm_fault_t ret = do_set_pmd(vmf, page); |
| if (!ret) { |
| /* The page is mapped successfully, reference consumed. */ |
| unlock_page(page); |
| return true; |
| } |
| } |
| |
| if (pmd_none(*vmf->pmd)) |
| pmd_install(mm, vmf->pmd, &vmf->prealloc_pte); |
| |
| /* See comment in handle_pte_fault() */ |
| if (pmd_devmap_trans_unstable(vmf->pmd)) { |
| unlock_page(page); |
| put_page(page); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static struct folio *next_uptodate_page(struct folio *folio, |
| struct address_space *mapping, |
| struct xa_state *xas, pgoff_t end_pgoff) |
| { |
| unsigned long max_idx; |
| |
| do { |
| if (!folio) |
| return NULL; |
| if (xas_retry(xas, folio)) |
| continue; |
| if (xa_is_value(folio)) |
| continue; |
| if (folio_test_locked(folio)) |
| continue; |
| if (!folio_try_get_rcu(folio)) |
| continue; |
| /* Has the page moved or been split? */ |
| if (unlikely(folio != xas_reload(xas))) |
| goto skip; |
| if (!folio_test_uptodate(folio) || folio_test_readahead(folio)) |
| goto skip; |
| if (!folio_trylock(folio)) |
| goto skip; |
| if (folio->mapping != mapping) |
| goto unlock; |
| if (!folio_test_uptodate(folio)) |
| goto unlock; |
| max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); |
| if (xas->xa_index >= max_idx) |
| goto unlock; |
| return folio; |
| unlock: |
| folio_unlock(folio); |
| skip: |
| folio_put(folio); |
| } while ((folio = xas_next_entry(xas, end_pgoff)) != NULL); |
| |
| return NULL; |
| } |
| |
| static inline struct folio *first_map_page(struct address_space *mapping, |
| struct xa_state *xas, |
| pgoff_t end_pgoff) |
| { |
| return next_uptodate_page(xas_find(xas, end_pgoff), |
|