| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Ram backed block device driver. |
| * |
| * Copyright (C) 2007 Nick Piggin |
| * Copyright (C) 2007 Novell Inc. |
| * |
| * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright |
| * of their respective owners. |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/initrd.h> |
| #include <linux/module.h> |
| #include <linux/moduleparam.h> |
| #include <linux/major.h> |
| #include <linux/blkdev.h> |
| #include <linux/bio.h> |
| #include <linux/highmem.h> |
| #include <linux/mutex.h> |
| #include <linux/radix-tree.h> |
| #include <linux/fs.h> |
| #include <linux/slab.h> |
| #include <linux/backing-dev.h> |
| |
| #include <linux/uaccess.h> |
| |
| #define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) |
| #define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT) |
| |
| /* |
| * Each block ramdisk device has a radix_tree brd_pages of pages that stores |
| * the pages containing the block device's contents. A brd page's ->index is |
| * its offset in PAGE_SIZE units. This is similar to, but in no way connected |
| * with, the kernel's pagecache or buffer cache (which sit above our block |
| * device). |
| */ |
| struct brd_device { |
| int brd_number; |
| |
| struct request_queue *brd_queue; |
| struct gendisk *brd_disk; |
| struct list_head brd_list; |
| |
| /* |
| * Backing store of pages and lock to protect it. This is the contents |
| * of the block device. |
| */ |
| spinlock_t brd_lock; |
| struct radix_tree_root brd_pages; |
| }; |
| |
| /* |
| * Look up and return a brd's page for a given sector. |
| */ |
| static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) |
| { |
| pgoff_t idx; |
| struct page *page; |
| |
| /* |
| * The page lifetime is protected by the fact that we have opened the |
| * device node -- brd pages will never be deleted under us, so we |
| * don't need any further locking or refcounting. |
| * |
| * This is strictly true for the radix-tree nodes as well (ie. we |
| * don't actually need the rcu_read_lock()), however that is not a |
| * documented feature of the radix-tree API so it is better to be |
| * safe here (we don't have total exclusion from radix tree updates |
| * here, only deletes). |
| */ |
| rcu_read_lock(); |
| idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */ |
| page = radix_tree_lookup(&brd->brd_pages, idx); |
| rcu_read_unlock(); |
| |
| BUG_ON(page && page->index != idx); |
| |
| return page; |
| } |
| |
| /* |
| * Look up and return a brd's page for a given sector. |
| * If one does not exist, allocate an empty page, and insert that. Then |
| * return it. |
| */ |
| static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) |
| { |
| pgoff_t idx; |
| struct page *page; |
| gfp_t gfp_flags; |
| |
| page = brd_lookup_page(brd, sector); |
| if (page) |
| return page; |
| |
| /* |
| * Must use NOIO because we don't want to recurse back into the |
| * block or filesystem layers from page reclaim. |
| */ |
| gfp_flags = GFP_NOIO | __GFP_ZERO | __GFP_HIGHMEM; |
| page = alloc_page(gfp_flags); |
| if (!page) |
| return NULL; |
| |
| if (radix_tree_preload(GFP_NOIO)) { |
| __free_page(page); |
| return NULL; |
| } |
| |
| spin_lock(&brd->brd_lock); |
| idx = sector >> PAGE_SECTORS_SHIFT; |
| page->index = idx; |
| if (radix_tree_insert(&brd->brd_pages, idx, page)) { |
| __free_page(page); |
| page = radix_tree_lookup(&brd->brd_pages, idx); |
| BUG_ON(!page); |
| BUG_ON(page->index != idx); |
| } |
| spin_unlock(&brd->brd_lock); |
| |
| radix_tree_preload_end(); |
| |
| return page; |
| } |
| |
| /* |
| * Free all backing store pages and radix tree. This must only be called when |
| * there are no other users of the device. |
| */ |
| #define FREE_BATCH 16 |
| static void brd_free_pages(struct brd_device *brd) |
| { |
| unsigned long pos = 0; |
| struct page *pages[FREE_BATCH]; |
| int nr_pages; |
| |
| do { |
| int i; |
| |
| nr_pages = radix_tree_gang_lookup(&brd->brd_pages, |
| (void **)pages, pos, FREE_BATCH); |
| |
| for (i = 0; i < nr_pages; i++) { |
| void *ret; |
| |
| BUG_ON(pages[i]->index < pos); |
| pos = pages[i]->index; |
| ret = radix_tree_delete(&brd->brd_pages, pos); |
| BUG_ON(!ret || ret != pages[i]); |
| __free_page(pages[i]); |
| } |
| |
| pos++; |
| |
| /* |
| * It takes 3.4 seconds to remove 80GiB ramdisk. |
| * So, we need cond_resched to avoid stalling the CPU. |
| */ |
| cond_resched(); |
| |
| /* |
| * This assumes radix_tree_gang_lookup always returns as |
| * many pages as possible. If the radix-tree code changes, |
| * so will this have to. |
| */ |
| } while (nr_pages == FREE_BATCH); |
| } |
| |
| /* |
| * copy_to_brd_setup must be called before copy_to_brd. It may sleep. |
| */ |
| static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n) |
| { |
| unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
| size_t copy; |
| |
| copy = min_t(size_t, n, PAGE_SIZE - offset); |
| if (!brd_insert_page(brd, sector)) |
| return -ENOSPC; |
| if (copy < n) { |
| sector += copy >> SECTOR_SHIFT; |
| if (!brd_insert_page(brd, sector)) |
| return -ENOSPC; |
| } |
| return 0; |
| } |
| |
| /* |
| * Copy n bytes from src to the brd starting at sector. Does not sleep. |
| */ |
| static void copy_to_brd(struct brd_device *brd, const void *src, |
| sector_t sector, size_t n) |
| { |
| struct page *page; |
| void *dst; |
| unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
| size_t copy; |
| |
| copy = min_t(size_t, n, PAGE_SIZE - offset); |
| page = brd_lookup_page(brd, sector); |
| BUG_ON(!page); |
| |
| dst = kmap_atomic(page); |
| memcpy(dst + offset, src, copy); |
| kunmap_atomic(dst); |
| |
| if (copy < n) { |
| src += copy; |
| sector += copy >> SECTOR_SHIFT; |
| copy = n - copy; |
| page = brd_lookup_page(brd, sector); |
| BUG_ON(!page); |
| |
| dst = kmap_atomic(page); |
| memcpy(dst, src, copy); |
| kunmap_atomic(dst); |
| } |
| } |
| |
| /* |
| * Copy n bytes to dst from the brd starting at sector. Does not sleep. |
| */ |
| static void copy_from_brd(void *dst, struct brd_device *brd, |
| sector_t sector, size_t n) |
| { |
| struct page *page; |
| void *src; |
| unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
| size_t copy; |
| |
| copy = min_t(size_t, n, PAGE_SIZE - offset); |
| page = brd_lookup_page(brd, sector); |
| if (page) { |
| src = kmap_atomic(page); |
| memcpy(dst, src + offset, copy); |
| kunmap_atomic(src); |
| } else |
| memset(dst, 0, copy); |
| |
| if (copy < n) { |
| dst += copy; |
| sector += copy >> SECTOR_SHIFT; |
| copy = n - copy; |
| page = brd_lookup_page(brd, sector); |
| if (page) { |
| src = kmap_atomic(page); |
| memcpy(dst, src, copy); |
| kunmap_atomic(src); |
| } else |
| memset(dst, 0, copy); |
| } |
| } |
| |
| /* |
| * Process a single bvec of a bio. |
| */ |
| static int brd_do_bvec(struct brd_device *brd, struct page *page, |
| unsigned int len, unsigned int off, unsigned int op, |
| sector_t sector) |
| { |
| void *mem; |
| int err = 0; |
| |
| if (op_is_write(op)) { |
| err = copy_to_brd_setup(brd, sector, len); |
| if (err) |
| goto out; |
| } |
| |
| mem = kmap_atomic(page); |
| if (!op_is_write(op)) { |
| copy_from_brd(mem + off, brd, sector, len); |
| flush_dcache_page(page); |
| } else { |
| flush_dcache_page(page); |
| copy_to_brd(brd, mem + off, sector, len); |
| } |
| kunmap_atomic(mem); |
| |
| out: |
| return err; |
| } |
| |
| static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio) |
| { |
| struct brd_device *brd = bio->bi_disk->private_data; |
| struct bio_vec bvec; |
| sector_t sector; |
| struct bvec_iter iter; |
| |
| sector = bio->bi_iter.bi_sector; |
| if (bio_end_sector(bio) > get_capacity(bio->bi_disk)) |
| goto io_error; |
| |
| bio_for_each_segment(bvec, bio, iter) { |
| unsigned int len = bvec.bv_len; |
| int err; |
| |
| err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, |
| bio_op(bio), sector); |
| if (err) |
| goto io_error; |
| sector += len >> SECTOR_SHIFT; |
| } |
| |
| bio_endio(bio); |
| return BLK_QC_T_NONE; |
| io_error: |
| bio_io_error(bio); |
| return BLK_QC_T_NONE; |
| } |
| |
| static int brd_rw_page(struct block_device *bdev, sector_t sector, |
| struct page *page, unsigned int op) |
| { |
| struct brd_device *brd = bdev->bd_disk->private_data; |
| int err; |
| |
| if (PageTransHuge(page)) |
| return -ENOTSUPP; |
| err = brd_do_bvec(brd, page, PAGE_SIZE, 0, op, sector); |
| page_endio(page, op_is_write(op), err); |
| return err; |
| } |
| |
| static const struct block_device_operations brd_fops = { |
| .owner = THIS_MODULE, |
| .rw_page = brd_rw_page, |
| }; |
| |
| /* |
| * And now the modules code and kernel interface. |
| */ |
| static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT; |
| module_param(rd_nr, int, 0444); |
| MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); |
| |
| unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE; |
| module_param(rd_size, ulong, 0444); |
| MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); |
| |
| static int max_part = 1; |
| module_param(max_part, int, 0444); |
| MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR); |
| MODULE_ALIAS("rd"); |
| |
| #ifndef MODULE |
| /* Legacy boot options - nonmodular */ |
| static int __init ramdisk_size(char *str) |
| { |
| rd_size = simple_strtol(str, NULL, 0); |
| return 1; |
| } |
| __setup("ramdisk_size=", ramdisk_size); |
| #endif |
| |
| /* |
| * The device scheme is derived from loop.c. Keep them in synch where possible |
| * (should share code eventually). |
| */ |
| static LIST_HEAD(brd_devices); |
| static DEFINE_MUTEX(brd_devices_mutex); |
| |
| static struct brd_device *brd_alloc(int i) |
| { |
| struct brd_device *brd; |
| struct gendisk *disk; |
| |
| brd = kzalloc(sizeof(*brd), GFP_KERNEL); |
| if (!brd) |
| goto out; |
| brd->brd_number = i; |
| spin_lock_init(&brd->brd_lock); |
| INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC); |
| |
| brd->brd_queue = blk_alloc_queue(GFP_KERNEL); |
| if (!brd->brd_queue) |
| goto out_free_dev; |
| |
| blk_queue_make_request(brd->brd_queue, brd_make_request); |
| blk_queue_max_hw_sectors(brd->brd_queue, 1024); |
| |
| /* This is so fdisk will align partitions on 4k, because of |
| * direct_access API needing 4k alignment, returning a PFN |
| * (This is only a problem on very small devices <= 4M, |
| * otherwise fdisk will align on 1M. Regardless this call |
| * is harmless) |
| */ |
| blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE); |
| disk = brd->brd_disk = alloc_disk(max_part); |
| if (!disk) |
| goto out_free_queue; |
| disk->major = RAMDISK_MAJOR; |
| disk->first_minor = i * max_part; |
| disk->fops = &brd_fops; |
| disk->private_data = brd; |
| disk->flags = GENHD_FL_EXT_DEVT; |
| sprintf(disk->disk_name, "ram%d", i); |
| set_capacity(disk, rd_size * 2); |
| brd->brd_queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO; |
| |
| /* Tell the block layer that this is not a rotational device */ |
| blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue); |
| blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, brd->brd_queue); |
| |
| return brd; |
| |
| out_free_queue: |
| blk_cleanup_queue(brd->brd_queue); |
| out_free_dev: |
| kfree(brd); |
| out: |
| return NULL; |
| } |
| |
| static void brd_free(struct brd_device *brd) |
| { |
| put_disk(brd->brd_disk); |
| blk_cleanup_queue(brd->brd_queue); |
| brd_free_pages(brd); |
| kfree(brd); |
| } |
| |
| static struct brd_device *brd_init_one(int i, bool *new) |
| { |
| struct brd_device *brd; |
| |
| *new = false; |
| list_for_each_entry(brd, &brd_devices, brd_list) { |
| if (brd->brd_number == i) |
| goto out; |
| } |
| |
| brd = brd_alloc(i); |
| if (brd) { |
| brd->brd_disk->queue = brd->brd_queue; |
| add_disk(brd->brd_disk); |
| list_add_tail(&brd->brd_list, &brd_devices); |
| } |
| *new = true; |
| out: |
| return brd; |
| } |
| |
| static void brd_del_one(struct brd_device *brd) |
| { |
| list_del(&brd->brd_list); |
| del_gendisk(brd->brd_disk); |
| brd_free(brd); |
| } |
| |
| static struct kobject *brd_probe(dev_t dev, int *part, void *data) |
| { |
| struct brd_device *brd; |
| struct kobject *kobj; |
| bool new; |
| |
| mutex_lock(&brd_devices_mutex); |
| brd = brd_init_one(MINOR(dev) / max_part, &new); |
| kobj = brd ? get_disk_and_module(brd->brd_disk) : NULL; |
| mutex_unlock(&brd_devices_mutex); |
| |
| if (new) |
| *part = 0; |
| |
| return kobj; |
| } |
| |
| static inline void brd_check_and_reset_par(void) |
| { |
| if (unlikely(!max_part)) |
| max_part = 1; |
| |
| /* |
| * make sure 'max_part' can be divided exactly by (1U << MINORBITS), |
| * otherwise, it is possiable to get same dev_t when adding partitions. |
| */ |
| if ((1U << MINORBITS) % max_part != 0) |
| max_part = 1UL << fls(max_part); |
| |
| if (max_part > DISK_MAX_PARTS) { |
| pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n", |
| DISK_MAX_PARTS, DISK_MAX_PARTS); |
| max_part = DISK_MAX_PARTS; |
| } |
| } |
| |
| static int __init brd_init(void) |
| { |
| struct brd_device *brd, *next; |
| int i; |
| |
| /* |
| * brd module now has a feature to instantiate underlying device |
| * structure on-demand, provided that there is an access dev node. |
| * |
| * (1) if rd_nr is specified, create that many upfront. else |
| * it defaults to CONFIG_BLK_DEV_RAM_COUNT |
| * (2) User can further extend brd devices by create dev node themselves |
| * and have kernel automatically instantiate actual device |
| * on-demand. Example: |
| * mknod /path/devnod_name b 1 X # 1 is the rd major |
| * fdisk -l /path/devnod_name |
| * If (X / max_part) was not already created it will be created |
| * dynamically. |
| */ |
| |
| if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) |
| return -EIO; |
| |
| brd_check_and_reset_par(); |
| |
| for (i = 0; i < rd_nr; i++) { |
| brd = brd_alloc(i); |
| if (!brd) |
| goto out_free; |
| list_add_tail(&brd->brd_list, &brd_devices); |
| } |
| |
| /* point of no return */ |
| |
| list_for_each_entry(brd, &brd_devices, brd_list) { |
| /* |
| * associate with queue just before adding disk for |
| * avoiding to mess up failure path |
| */ |
| brd->brd_disk->queue = brd->brd_queue; |
| add_disk(brd->brd_disk); |
| } |
| |
| blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS, |
| THIS_MODULE, brd_probe, NULL, NULL); |
| |
| pr_info("brd: module loaded\n"); |
| return 0; |
| |
| out_free: |
| list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { |
| list_del(&brd->brd_list); |
| brd_free(brd); |
| } |
| unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
| |
| pr_info("brd: module NOT loaded !!!\n"); |
| return -ENOMEM; |
| } |
| |
| static void __exit brd_exit(void) |
| { |
| struct brd_device *brd, *next; |
| |
| list_for_each_entry_safe(brd, next, &brd_devices, brd_list) |
| brd_del_one(brd); |
| |
| blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS); |
| unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
| |
| pr_info("brd: module unloaded\n"); |
| } |
| |
| module_init(brd_init); |
| module_exit(brd_exit); |
| |