crypto/async_tx/async_xor.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * xor offload engine api
  *
  * Copyright © 2006, Intel Corporation.
  *
  *      Dan Williams <dan.j.williams@intel.com>
  *
  *      with architecture considerations by:
  *      Neil Brown <neilb@suse.de>
  *      Jeff Garzik <jeff@garzik.org>
  */
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/raid/xor.h>
 #include <linux/async_tx.h>

 /* do_async_xor - dma map the pages and perform the xor with an engine */
 static __async_inline struct dma_async_tx_descriptor *
 do_async_xor(struct dma_chan *chan, struct dmaengine_unmap_data *unmap,
 	     struct async_submit_ctl *submit)
 {
 	struct dma_device *dma = chan->device;
 	struct dma_async_tx_descriptor *tx = NULL;
 	dma_async_tx_callback cb_fn_orig = submit->cb_fn;
 	void *cb_param_orig = submit->cb_param;
 	enum async_tx_flags flags_orig = submit->flags;
 	enum dma_ctrl_flags dma_flags = 0;
 	int src_cnt = unmap->to_cnt;
 	int xor_src_cnt;
 	dma_addr_t dma_dest = unmap->addr[unmap->to_cnt];
 	dma_addr_t *src_list = unmap->addr;

 	while (src_cnt) {
 		dma_addr_t tmp;

 		submit->flags = flags_orig;
 		xor_src_cnt = min(src_cnt, (int)dma->max_xor);
 		/* if we are submitting additional xors, leave the chain open
 		 * and clear the callback parameters
 		 */
 		if (src_cnt > xor_src_cnt) {
 			submit->flags &= ~ASYNC_TX_ACK;
 			submit->flags |= ASYNC_TX_FENCE;
 			submit->cb_fn = NULL;
 			submit->cb_param = NULL;
 		} else {
 			submit->cb_fn = cb_fn_orig;
 			submit->cb_param = cb_param_orig;
 		}
 		if (submit->cb_fn)
 			dma_flags |= DMA_PREP_INTERRUPT;
 		if (submit->flags & ASYNC_TX_FENCE)
 			dma_flags |= DMA_PREP_FENCE;

 		/* Drivers force forward progress in case they can not provide a
 		 * descriptor
 		 */
 		tmp = src_list[0];
 		if (src_list > unmap->addr)
 			src_list[0] = dma_dest;
 		tx = dma->device_prep_dma_xor(chan, dma_dest, src_list,
 					      xor_src_cnt, unmap->len,
 					      dma_flags);

 		if (unlikely(!tx))
 			async_tx_quiesce(&submit->depend_tx);

 		/* spin wait for the preceding transactions to complete */
 		while (unlikely(!tx)) {
 			dma_async_issue_pending(chan);
 			tx = dma->device_prep_dma_xor(chan, dma_dest,
 						      src_list,
 						      xor_src_cnt, unmap->len,
 						      dma_flags);
 		}
 		src_list[0] = tmp;

 		dma_set_unmap(tx, unmap);
 		async_tx_submit(chan, tx, submit);
 		submit->depend_tx = tx;

 		if (src_cnt > xor_src_cnt) {
 			/* drop completed sources */
 			src_cnt -= xor_src_cnt;
 			/* use the intermediate result a source */
 			src_cnt++;
 			src_list += xor_src_cnt - 1;
 		} else
 			break;
 	}

 	return tx;
 }

 static void
 do_sync_xor_offs(struct page *dest, unsigned int offset,
 		struct page **src_list, unsigned int *src_offs,
 	    int src_cnt, size_t len, struct async_submit_ctl *submit)
 {
 	int i;
 	int xor_src_cnt = 0;
 	int src_off = 0;
 	void *dest_buf;
 	void **srcs;

 	if (submit->scribble)
 		srcs = submit->scribble;
 	else
 		srcs = (void **) src_list;

 	/* convert to buffer pointers */
 	for (i = 0; i < src_cnt; i++)
 		if (src_list[i])
 			srcs[xor_src_cnt++] = page_address(src_list[i]) +
 				(src_offs ? src_offs[i] : offset);
 	src_cnt = xor_src_cnt;
 	/* set destination address */
 	dest_buf = page_address(dest) + offset;

 	if (submit->flags & ASYNC_TX_XOR_ZERO_DST)
 		memset(dest_buf, 0, len);

 	while (src_cnt > 0) {
 		/* process up to 'MAX_XOR_BLOCKS' sources */
 		xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
 		xor_blocks(xor_src_cnt, len, dest_buf, &srcs[src_off]);

 		/* drop completed sources */
 		src_cnt -= xor_src_cnt;
 		src_off += xor_src_cnt;
 	}

 	async_tx_sync_epilog(submit);
 }

 static inline bool
 dma_xor_aligned_offsets(struct dma_device *device, unsigned int offset,
 		unsigned int *src_offs, int src_cnt, int len)
 {
 	int i;

 	if (!is_dma_xor_aligned(device, offset, 0, len))
 		return false;

 	if (!src_offs)
 		return true;

 	for (i = 0; i < src_cnt; i++) {
 		if (!is_dma_xor_aligned(device, src_offs[i], 0, len))
 			return false;
 	}
 	return true;
 }

 /**
  * async_xor_offs - attempt to xor a set of blocks with a dma engine.
  * @dest: destination page
  * @offset: dst offset to start transaction
  * @src_list: array of source pages
  * @src_offs: array of source pages offset, NULL means common src/dst offset
  * @src_cnt: number of source pages
  * @len: length in bytes
  * @submit: submission / completion modifiers
  *
  * honored flags: ASYNC_TX_ACK, ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DST
  *
  * xor_blocks always uses the dest as a source so the
  * ASYNC_TX_XOR_ZERO_DST flag must be set to not include dest data in
  * the calculation.  The assumption with dma engines is that they only
  * use the destination buffer as a source when it is explicitly specified
  * in the source list.
  *
  * src_list note: if the dest is also a source it must be at index zero.
  * The contents of this array will be overwritten if a scribble region
  * is not specified.
  */
 struct dma_async_tx_descriptor *
 async_xor_offs(struct page *dest, unsigned int offset,
 		struct page **src_list, unsigned int *src_offs,
 		int src_cnt, size_t len, struct async_submit_ctl *submit)
 {
 	struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR,
 						      &dest, 1, src_list,
 						      src_cnt, len);
 	struct dma_device *device = chan ? chan->device : NULL;
 	struct dmaengine_unmap_data *unmap = NULL;

 	BUG_ON(src_cnt <= 1);

 	if (device)
 		unmap = dmaengine_get_unmap_data(device->dev, src_cnt+1, GFP_NOWAIT);

 	if (unmap && dma_xor_aligned_offsets(device, offset,
 				src_offs, src_cnt, len)) {
 		struct dma_async_tx_descriptor *tx;
 		int i, j;

 		/* run the xor asynchronously */
 		pr_debug("%s (async): len: %zu\n", __func__, len);

 		unmap->len = len;
 		for (i = 0, j = 0; i < src_cnt; i++) {
 			if (!src_list[i])
 				continue;
 			unmap->to_cnt++;
 			unmap->addr[j++] = dma_map_page(device->dev, src_list[i],
 					src_offs ? src_offs[i] : offset,
 					len, DMA_TO_DEVICE);
 		}

 		/* map it bidirectional as it may be re-used as a source */
 		unmap->addr[j] = dma_map_page(device->dev, dest, offset, len,
 					      DMA_BIDIRECTIONAL);
 		unmap->bidi_cnt = 1;

 		tx = do_async_xor(chan, unmap, submit);
 		dmaengine_unmap_put(unmap);
 		return tx;
 	} else {
 		dmaengine_unmap_put(unmap);
 		/* run the xor synchronously */
 		pr_debug("%s (sync): len: %zu\n", __func__, len);
 		WARN_ONCE(chan, "%s: no space for dma address conversion\n",
 			  __func__);

 		/* in the sync case the dest is an implied source
 		 * (assumes the dest is the first source)
 		 */
 		if (submit->flags & ASYNC_TX_XOR_DROP_DST) {
 			src_cnt--;
 			src_list++;
 			if (src_offs)
 				src_offs++;
 		}

 		/* wait for any prerequisite operations */
 		async_tx_quiesce(&submit->depend_tx);

 		do_sync_xor_offs(dest, offset, src_list, src_offs,
 				src_cnt, len, submit);

 		return NULL;
 	}
 }
 EXPORT_SYMBOL_GPL(async_xor_offs);

 /**
  * async_xor - attempt to xor a set of blocks with a dma engine.
  * @dest: destination page
  * @src_list: array of source pages
  * @offset: common src/dst offset to start transaction
  * @src_cnt: number of source pages
  * @len: length in bytes
  * @submit: submission / completion modifiers
  *
  * honored flags: ASYNC_TX_ACK, ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DST
  *
  * xor_blocks always uses the dest as a source so the
  * ASYNC_TX_XOR_ZERO_DST flag must be set to not include dest data in
  * the calculation.  The assumption with dma engines is that they only
  * use the destination buffer as a source when it is explicitly specified
  * in the source list.
  *
  * src_list note: if the dest is also a source it must be at index zero.
  * The contents of this array will be overwritten if a scribble region
  * is not specified.
  */
 struct dma_async_tx_descriptor *
 async_xor(struct page *dest, struct page **src_list, unsigned int offset,
 	  int src_cnt, size_t len, struct async_submit_ctl *submit)
 {
 	return async_xor_offs(dest, offset, src_list, NULL,
 			src_cnt, len, submit);
 }
 EXPORT_SYMBOL_GPL(async_xor);

 static int page_is_zero(struct page *p, unsigned int offset, size_t len)
 {
 	return !memchr_inv(page_address(p) + offset, 0, len);
 }

 static inline struct dma_chan *
 xor_val_chan(struct async_submit_ctl *submit, struct page *dest,
 		 struct page **src_list, int src_cnt, size_t len)
 {
 	#ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
 	return NULL;
 	#endif
 	return async_tx_find_channel(submit, DMA_XOR_VAL, &dest, 1, src_list,
 				     src_cnt, len);
 }

 /**
  * async_xor_val_offs - attempt a xor parity check with a dma engine.
  * @dest: destination page used if the xor is performed synchronously
  * @offset: des offset in pages to start transaction
  * @src_list: array of source pages
  * @src_offs: array of source pages offset, NULL means common src/det offset
  * @src_cnt: number of source pages
  * @len: length in bytes
  * @result: 0 if sum == 0 else non-zero
  * @submit: submission / completion modifiers
  *
  * honored flags: ASYNC_TX_ACK
  *
  * src_list note: if the dest is also a source it must be at index zero.
  * The contents of this array will be overwritten if a scribble region
  * is not specified.
  */
 struct dma_async_tx_descriptor *
 async_xor_val_offs(struct page *dest, unsigned int offset,
 		struct page **src_list, unsigned int *src_offs,
 		int src_cnt, size_t len, enum sum_check_flags *result,
 		struct async_submit_ctl *submit)
 {
 	struct dma_chan *chan = xor_val_chan(submit, dest, src_list, src_cnt, len);
 	struct dma_device *device = chan ? chan->device : NULL;
 	struct dma_async_tx_descriptor *tx = NULL;
 	struct dmaengine_unmap_data *unmap = NULL;

 	BUG_ON(src_cnt <= 1);

 	if (device)
 		unmap = dmaengine_get_unmap_data(device->dev, src_cnt, GFP_NOWAIT);

 	if (unmap && src_cnt <= device->max_xor &&
 	    dma_xor_aligned_offsets(device, offset, src_offs, src_cnt, len)) {
 		unsigned long dma_prep_flags = 0;
 		int i;

 		pr_debug("%s: (async) len: %zu\n", __func__, len);

 		if (submit->cb_fn)
 			dma_prep_flags |= DMA_PREP_INTERRUPT;
 		if (submit->flags & ASYNC_TX_FENCE)
 			dma_prep_flags |= DMA_PREP_FENCE;

 		for (i = 0; i < src_cnt; i++) {
 			unmap->addr[i] = dma_map_page(device->dev, src_list[i],
 					src_offs ? src_offs[i] : offset,
 					len, DMA_TO_DEVICE);
 			unmap->to_cnt++;
 		}
 		unmap->len = len;

 		tx = device->device_prep_dma_xor_val(chan, unmap->addr, src_cnt,
 						     len, result,
 						     dma_prep_flags);
 		if (unlikely(!tx)) {
 			async_tx_quiesce(&submit->depend_tx);

 			while (!tx) {
 				dma_async_issue_pending(chan);
 				tx = device->device_prep_dma_xor_val(chan,
 					unmap->addr, src_cnt, len, result,
 					dma_prep_flags);
 			}
 		}
 		dma_set_unmap(tx, unmap);
 		async_tx_submit(chan, tx, submit);
 	} else {
 		enum async_tx_flags flags_orig = submit->flags;

 		pr_debug("%s: (sync) len: %zu\n", __func__, len);
 		WARN_ONCE(device && src_cnt <= device->max_xor,
 			  "%s: no space for dma address conversion\n",
 			  __func__);

 		submit->flags |= ASYNC_TX_XOR_DROP_DST;
 		submit->flags &= ~ASYNC_TX_ACK;

 		tx = async_xor_offs(dest, offset, src_list, src_offs,
 				src_cnt, len, submit);

 		async_tx_quiesce(&tx);

 		*result = !page_is_zero(dest, offset, len) << SUM_CHECK_P;

 		async_tx_sync_epilog(submit);
 		submit->flags = flags_orig;
 	}
 	dmaengine_unmap_put(unmap);

 	return tx;
 }
 EXPORT_SYMBOL_GPL(async_xor_val_offs);

 /**
  * async_xor_val - attempt a xor parity check with a dma engine.
  * @dest: destination page used if the xor is performed synchronously
  * @src_list: array of source pages
  * @offset: offset in pages to start transaction
  * @src_cnt: number of source pages
  * @len: length in bytes
  * @result: 0 if sum == 0 else non-zero
  * @submit: submission / completion modifiers
  *
  * honored flags: ASYNC_TX_ACK
  *
  * src_list note: if the dest is also a source it must be at index zero.
  * The contents of this array will be overwritten if a scribble region
  * is not specified.
  */
 struct dma_async_tx_descriptor *
 async_xor_val(struct page *dest, struct page **src_list, unsigned int offset,
 	      int src_cnt, size_t len, enum sum_check_flags *result,
 	      struct async_submit_ctl *submit)
 {
 	return async_xor_val_offs(dest, offset, src_list, NULL, src_cnt,
 			len, result, submit);
 }
 EXPORT_SYMBOL_GPL(async_xor_val);

 MODULE_AUTHOR("Intel Corporation");
 MODULE_DESCRIPTION("asynchronous xor/xor-zero-sum api");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* xor offload engine api
	*
	* Copyright © 2006, Intel Corporation.
	*
	* Dan Williams <dan.j.williams@intel.com>
	*
	* with architecture considerations by:
	* Neil Brown <neilb@suse.de>
	* Jeff Garzik <jeff@garzik.org>
	*/
	#include <linux/kernel.h>
	#include <linux/interrupt.h>
	#include <linux/module.h>
	#include <linux/mm.h>
	#include <linux/dma-mapping.h>
	#include <linux/raid/xor.h>
	#include <linux/async_tx.h>

	/* do_async_xor - dma map the pages and perform the xor with an engine */
	static __async_inline struct dma_async_tx_descriptor *
	do_async_xor(struct dma_chan chan, struct dmaengine_unmap_data unmap,
	struct async_submit_ctl *submit)
	{
	struct dma_device *dma = chan->device;
	struct dma_async_tx_descriptor *tx = NULL;
	dma_async_tx_callback cb_fn_orig = submit->cb_fn;
	void *cb_param_orig = submit->cb_param;
	enum async_tx_flags flags_orig = submit->flags;
	enum dma_ctrl_flags dma_flags = 0;
	int src_cnt = unmap->to_cnt;
	int xor_src_cnt;
	dma_addr_t dma_dest = unmap->addr[unmap->to_cnt];
	dma_addr_t *src_list = unmap->addr;

	while (src_cnt) {
	dma_addr_t tmp;

	submit->flags = flags_orig;
	xor_src_cnt = min(src_cnt, (int)dma->max_xor);
	/* if we are submitting additional xors, leave the chain open
	* and clear the callback parameters
	*/
	if (src_cnt > xor_src_cnt) {
	submit->flags &= ~ASYNC_TX_ACK;
	submit->flags \|= ASYNC_TX_FENCE;
	submit->cb_fn = NULL;
	submit->cb_param = NULL;
	} else {
	submit->cb_fn = cb_fn_orig;
	submit->cb_param = cb_param_orig;
	}
	if (submit->cb_fn)
	dma_flags \|= DMA_PREP_INTERRUPT;
	if (submit->flags & ASYNC_TX_FENCE)
	dma_flags \|= DMA_PREP_FENCE;

	/* Drivers force forward progress in case they can not provide a
	* descriptor
	*/
	tmp = src_list[0];
	if (src_list > unmap->addr)
	src_list[0] = dma_dest;
	tx = dma->device_prep_dma_xor(chan, dma_dest, src_list,
	xor_src_cnt, unmap->len,
	dma_flags);

	if (unlikely(!tx))
	async_tx_quiesce(&submit->depend_tx);

	/* spin wait for the preceding transactions to complete */
	while (unlikely(!tx)) {
	dma_async_issue_pending(chan);
	tx = dma->device_prep_dma_xor(chan, dma_dest,
	src_list,
	xor_src_cnt, unmap->len,
	dma_flags);
	}
	src_list[0] = tmp;

	dma_set_unmap(tx, unmap);
	async_tx_submit(chan, tx, submit);
	submit->depend_tx = tx;

	if (src_cnt > xor_src_cnt) {
	/* drop completed sources */
	src_cnt -= xor_src_cnt;
	/* use the intermediate result a source */
	src_cnt++;
	src_list += xor_src_cnt - 1;
	} else
	break;
	}

	return tx;
	}

	static void
	do_sync_xor_offs(struct page *dest, unsigned int offset,
	struct page *src_list, unsigned int src_offs,
	int src_cnt, size_t len, struct async_submit_ctl *submit)
	{
	int i;
	int xor_src_cnt = 0;
	int src_off = 0;
	void *dest_buf;
	void **srcs;

	if (submit->scribble)
	srcs = submit->scribble;
	else
	srcs = (void **) src_list;

	/* convert to buffer pointers */
	for (i = 0; i < src_cnt; i++)
	if (src_list[i])
	srcs[xor_src_cnt++] = page_address(src_list[i]) +
	(src_offs ? src_offs[i] : offset);
	src_cnt = xor_src_cnt;
	/* set destination address */
	dest_buf = page_address(dest) + offset;

	if (submit->flags & ASYNC_TX_XOR_ZERO_DST)
	memset(dest_buf, 0, len);

	while (src_cnt > 0) {
	/* process up to 'MAX_XOR_BLOCKS' sources */
	xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
	xor_blocks(xor_src_cnt, len, dest_buf, &srcs[src_off]);

	/* drop completed sources */
	src_cnt -= xor_src_cnt;
	src_off += xor_src_cnt;
	}

	async_tx_sync_epilog(submit);
	}

	static inline bool
	dma_xor_aligned_offsets(struct dma_device *device, unsigned int offset,
	unsigned int *src_offs, int src_cnt, int len)
	{
	int i;

	if (!is_dma_xor_aligned(device, offset, 0, len))
	return false;

	if (!src_offs)
	return true;

	for (i = 0; i < src_cnt; i++) {
	if (!is_dma_xor_aligned(device, src_offs[i], 0, len))
	return false;
	}
	return true;
	}

	/**
	* async_xor_offs - attempt to xor a set of blocks with a dma engine.
	* @dest: destination page
	* @offset: dst offset to start transaction
	* @src_list: array of source pages
	* @src_offs: array of source pages offset, NULL means common src/dst offset
	* @src_cnt: number of source pages
	* @len: length in bytes
	* @submit: submission / completion modifiers
	*
	* honored flags: ASYNC_TX_ACK, ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DST
	*
	* xor_blocks always uses the dest as a source so the
	* ASYNC_TX_XOR_ZERO_DST flag must be set to not include dest data in
	* the calculation. The assumption with dma engines is that they only
	* use the destination buffer as a source when it is explicitly specified
	* in the source list.
	*
	* src_list note: if the dest is also a source it must be at index zero.
	* The contents of this array will be overwritten if a scribble region
	* is not specified.
	*/
	struct dma_async_tx_descriptor *
	async_xor_offs(struct page *dest, unsigned int offset,
	struct page *src_list, unsigned int src_offs,
	int src_cnt, size_t len, struct async_submit_ctl *submit)
	{
	struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR,
	&dest, 1, src_list,
	src_cnt, len);
	struct dma_device *device = chan ? chan->device : NULL;
	struct dmaengine_unmap_data *unmap = NULL;

	BUG_ON(src_cnt <= 1);

	if (device)
	unmap = dmaengine_get_unmap_data(device->dev, src_cnt+1, GFP_NOWAIT);

	if (unmap && dma_xor_aligned_offsets(device, offset,
	src_offs, src_cnt, len)) {
	struct dma_async_tx_descriptor *tx;
	int i, j;

	/* run the xor asynchronously */
	pr_debug("%s (async): len: %zu\n", __func__, len);

	unmap->len = len;
	for (i = 0, j = 0; i < src_cnt; i++) {
	if (!src_list[i])
	continue;
	unmap->to_cnt++;
	unmap->addr[j++] = dma_map_page(device->dev, src_list[i],
	src_offs ? src_offs[i] : offset,
	len, DMA_TO_DEVICE);
	}

	/* map it bidirectional as it may be re-used as a source */
	unmap->addr[j] = dma_map_page(device->dev, dest, offset, len,
	DMA_BIDIRECTIONAL);
	unmap->bidi_cnt = 1;

	tx = do_async_xor(chan, unmap, submit);
	dmaengine_unmap_put(unmap);
	return tx;
	} else {
	dmaengine_unmap_put(unmap);
	/* run the xor synchronously */
	pr_debug("%s (sync): len: %zu\n", __func__, len);
	WARN_ONCE(chan, "%s: no space for dma address conversion\n",
	__func__);

	/* in the sync case the dest is an implied source
	* (assumes the dest is the first source)
	*/
	if (submit->flags & ASYNC_TX_XOR_DROP_DST) {
	src_cnt--;
	src_list++;
	if (src_offs)
	src_offs++;
	}

	/* wait for any prerequisite operations */
	async_tx_quiesce(&submit->depend_tx);

	do_sync_xor_offs(dest, offset, src_list, src_offs,
	src_cnt, len, submit);

	return NULL;
	}
	}
	EXPORT_SYMBOL_GPL(async_xor_offs);

	/**
	* async_xor - attempt to xor a set of blocks with a dma engine.
	* @dest: destination page
	* @src_list: array of source pages
	* @offset: common src/dst offset to start transaction
	* @src_cnt: number of source pages
	* @len: length in bytes
	* @submit: submission / completion modifiers
	*
	* honored flags: ASYNC_TX_ACK, ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DST
	*
	* xor_blocks always uses the dest as a source so the
	* ASYNC_TX_XOR_ZERO_DST flag must be set to not include dest data in
	* the calculation. The assumption with dma engines is that they only
	* use the destination buffer as a source when it is explicitly specified
	* in the source list.
	*
	* src_list note: if the dest is also a source it must be at index zero.
	* The contents of this array will be overwritten if a scribble region
	* is not specified.
	*/
	struct dma_async_tx_descriptor *
	async_xor(struct page dest, struct page *src_list, unsigned int offset,
	int src_cnt, size_t len, struct async_submit_ctl *submit)
	{
	return async_xor_offs(dest, offset, src_list, NULL,
	src_cnt, len, submit);
	}
	EXPORT_SYMBOL_GPL(async_xor);

	static int page_is_zero(struct page *p, unsigned int offset, size_t len)
	{
	return !memchr_inv(page_address(p) + offset, 0, len);
	}

	static inline struct dma_chan *
	xor_val_chan(struct async_submit_ctl submit, struct page dest,
	struct page **src_list, int src_cnt, size_t len)
	{
	#ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
	return NULL;
	#endif
	return async_tx_find_channel(submit, DMA_XOR_VAL, &dest, 1, src_list,
	src_cnt, len);
	}

	/**
	* async_xor_val_offs - attempt a xor parity check with a dma engine.
	* @dest: destination page used if the xor is performed synchronously
	* @offset: des offset in pages to start transaction
	* @src_list: array of source pages
	* @src_offs: array of source pages offset, NULL means common src/det offset
	* @src_cnt: number of source pages
	* @len: length in bytes
	* @result: 0 if sum == 0 else non-zero
	* @submit: submission / completion modifiers
	*
	* honored flags: ASYNC_TX_ACK
	*
	* src_list note: if the dest is also a source it must be at index zero.
	* The contents of this array will be overwritten if a scribble region
	* is not specified.
	*/
	struct dma_async_tx_descriptor *
	async_xor_val_offs(struct page *dest, unsigned int offset,
	struct page *src_list, unsigned int src_offs,
	int src_cnt, size_t len, enum sum_check_flags *result,
	struct async_submit_ctl *submit)
	{
	struct dma_chan *chan = xor_val_chan(submit, dest, src_list, src_cnt, len);
	struct dma_device *device = chan ? chan->device : NULL;
	struct dma_async_tx_descriptor *tx = NULL;
	struct dmaengine_unmap_data *unmap = NULL;

	BUG_ON(src_cnt <= 1);

	if (device)
	unmap = dmaengine_get_unmap_data(device->dev, src_cnt, GFP_NOWAIT);

	if (unmap && src_cnt <= device->max_xor &&
	dma_xor_aligned_offsets(device, offset, src_offs, src_cnt, len)) {
	unsigned long dma_prep_flags = 0;
	int i;

	pr_debug("%s: (async) len: %zu\n", __func__, len);

	if (submit->cb_fn)
	dma_prep_flags \|= DMA_PREP_INTERRUPT;
	if (submit->flags & ASYNC_TX_FENCE)
	dma_prep_flags \|= DMA_PREP_FENCE;

	for (i = 0; i < src_cnt; i++) {
	unmap->addr[i] = dma_map_page(device->dev, src_list[i],
	src_offs ? src_offs[i] : offset,
	len, DMA_TO_DEVICE);
	unmap->to_cnt++;
	}
	unmap->len = len;

	tx = device->device_prep_dma_xor_val(chan, unmap->addr, src_cnt,
	len, result,
	dma_prep_flags);
	if (unlikely(!tx)) {
	async_tx_quiesce(&submit->depend_tx);

	while (!tx) {
	dma_async_issue_pending(chan);
	tx = device->device_prep_dma_xor_val(chan,
	unmap->addr, src_cnt, len, result,
	dma_prep_flags);
	}
	}
	dma_set_unmap(tx, unmap);
	async_tx_submit(chan, tx, submit);
	} else {
	enum async_tx_flags flags_orig = submit->flags;

	pr_debug("%s: (sync) len: %zu\n", __func__, len);
	WARN_ONCE(device && src_cnt <= device->max_xor,
	"%s: no space for dma address conversion\n",
	__func__);

	submit->flags \|= ASYNC_TX_XOR_DROP_DST;
	submit->flags &= ~ASYNC_TX_ACK;

	tx = async_xor_offs(dest, offset, src_list, src_offs,
	src_cnt, len, submit);

	async_tx_quiesce(&tx);

	*result = !page_is_zero(dest, offset, len) << SUM_CHECK_P;

	async_tx_sync_epilog(submit);
	submit->flags = flags_orig;
	}
	dmaengine_unmap_put(unmap);

	return tx;
	}
	EXPORT_SYMBOL_GPL(async_xor_val_offs);

	/**
	* async_xor_val - attempt a xor parity check with a dma engine.
	* @dest: destination page used if the xor is performed synchronously
	* @src_list: array of source pages
	* @offset: offset in pages to start transaction
	* @src_cnt: number of source pages
	* @len: length in bytes
	* @result: 0 if sum == 0 else non-zero
	* @submit: submission / completion modifiers
	*
	* honored flags: ASYNC_TX_ACK
	*
	* src_list note: if the dest is also a source it must be at index zero.
	* The contents of this array will be overwritten if a scribble region
	* is not specified.
	*/
	struct dma_async_tx_descriptor *
	async_xor_val(struct page dest, struct page *src_list, unsigned int offset,
	int src_cnt, size_t len, enum sum_check_flags *result,
	struct async_submit_ctl *submit)
	{
	return async_xor_val_offs(dest, offset, src_list, NULL, src_cnt,
	len, result, submit);
	}
	EXPORT_SYMBOL_GPL(async_xor_val);

	MODULE_AUTHOR("Intel Corporation");
	MODULE_DESCRIPTION("asynchronous xor/xor-zero-sum api");
	MODULE_LICENSE("GPL");