block/blk-lib.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Functions related to generic helpers functions
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/scatterlist.h>

 #include "blk.h"

 struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp)
 {
 	struct bio *new = bio_alloc(gfp, nr_pages);

 	if (bio) {
 		bio_chain(bio, new);
 		submit_bio(bio);
 	}

 	return new;
 }

 int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, int flags,
 		struct bio **biop)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 	struct bio *bio = *biop;
 	unsigned int op;
 	sector_t bs_mask, part_offset = 0;

 	if (!q)
 		return -ENXIO;

 	if (bdev_read_only(bdev))
 		return -EPERM;

 	if (flags & BLKDEV_DISCARD_SECURE) {
 		if (!blk_queue_secure_erase(q))
 			return -EOPNOTSUPP;
 		op = REQ_OP_SECURE_ERASE;
 	} else {
 		if (!blk_queue_discard(q))
 			return -EOPNOTSUPP;
 		op = REQ_OP_DISCARD;
 	}

 	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
 	if ((sector | nr_sects) & bs_mask)
 		return -EINVAL;

 	if (!nr_sects)
 		return -EINVAL;

 	/* In case the discard request is in a partition */
 	if (bdev->bd_partno)
 		part_offset = bdev->bd_part->start_sect;

 	while (nr_sects) {
 		sector_t granularity_aligned_lba, req_sects;
 		sector_t sector_mapped = sector + part_offset;

 		granularity_aligned_lba = round_up(sector_mapped,
 				q->limits.discard_granularity >> SECTOR_SHIFT);

 		/*
 		 * Check whether the discard bio starts at a discard_granularity
 		 * aligned LBA,
 		 * - If no: set (granularity_aligned_lba - sector_mapped) to
 		 *   bi_size of the first split bio, then the second bio will
 		 *   start at a discard_granularity aligned LBA on the device.
 		 * - If yes: use bio_aligned_discard_max_sectors() as the max
 		 *   possible bi_size of the first split bio. Then when this bio
 		 *   is split in device drive, the split ones are very probably
 		 *   to be aligned to discard_granularity of the device's queue.
 		 */
 		if (granularity_aligned_lba == sector_mapped)
 			req_sects = min_t(sector_t, nr_sects,
 					  bio_aligned_discard_max_sectors(q));
 		else
 			req_sects = min_t(sector_t, nr_sects,
 					  granularity_aligned_lba - sector_mapped);

 		WARN_ON_ONCE((req_sects << 9) > UINT_MAX);

 		bio = blk_next_bio(bio, 0, gfp_mask);
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio_set_op_attrs(bio, op, 0);

 		bio->bi_iter.bi_size = req_sects << 9;
 		sector += req_sects;
 		nr_sects -= req_sects;

 		/*
 		 * We can loop for a long time in here, if someone does
 		 * full device discards (like mkfs). Be nice and allow
 		 * us to schedule out to avoid softlocking if preempt
 		 * is disabled.
 		 */
 		cond_resched();
 	}

 	*biop = bio;
 	return 0;
 }
 EXPORT_SYMBOL(__blkdev_issue_discard);

 /**
  * blkdev_issue_discard - queue a discard
  * @bdev:	blockdev to issue discard for
  * @sector:	start sector
  * @nr_sects:	number of sectors to discard
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @flags:	BLKDEV_DISCARD_* flags to control behaviour
  *
  * Description:
  *    Issue a discard request for the sectors in question.
  */
 int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
 {
 	struct bio *bio = NULL;
 	struct blk_plug plug;
 	int ret;

 	blk_start_plug(&plug);
 	ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,
 			&bio);
 	if (!ret && bio) {
 		ret = submit_bio_wait(bio);
 		if (ret == -EOPNOTSUPP)
 			ret = 0;
 		bio_put(bio);
 	}
 	blk_finish_plug(&plug);

 	return ret;
 }
 EXPORT_SYMBOL(blkdev_issue_discard);

 /**
  * __blkdev_issue_write_same - generate number of bios with same page
  * @bdev:	target blockdev
  * @sector:	start sector
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @page:	page containing data to write
  * @biop:	pointer to anchor bio
  *
  * Description:
  *  Generate and issue number of bios(REQ_OP_WRITE_SAME) with same page.
  */
 static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct page *page,
 		struct bio **biop)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 	unsigned int max_write_same_sectors;
 	struct bio *bio = *biop;
 	sector_t bs_mask;

 	if (!q)
 		return -ENXIO;

 	if (bdev_read_only(bdev))
 		return -EPERM;

 	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
 	if ((sector | nr_sects) & bs_mask)
 		return -EINVAL;

 	if (!bdev_write_same(bdev))
 		return -EOPNOTSUPP;

 	/* Ensure that max_write_same_sectors doesn't overflow bi_size */
 	max_write_same_sectors = bio_allowed_max_sectors(q);

 	while (nr_sects) {
 		bio = blk_next_bio(bio, 1, gfp_mask);
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio->bi_vcnt = 1;
 		bio->bi_io_vec->bv_page = page;
 		bio->bi_io_vec->bv_offset = 0;
 		bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
 		bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);

 		if (nr_sects > max_write_same_sectors) {
 			bio->bi_iter.bi_size = max_write_same_sectors << 9;
 			nr_sects -= max_write_same_sectors;
 			sector += max_write_same_sectors;
 		} else {
 			bio->bi_iter.bi_size = nr_sects << 9;
 			nr_sects = 0;
 		}
 		cond_resched();
 	}

 	*biop = bio;
 	return 0;
 }

 /**
  * blkdev_issue_write_same - queue a write same operation
  * @bdev:	target blockdev
  * @sector:	start sector
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @page:	page containing data
  *
  * Description:
  *    Issue a write same request for the sectors in question.
  */
 int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 				sector_t nr_sects, gfp_t gfp_mask,
 				struct page *page)
 {
 	struct bio *bio = NULL;
 	struct blk_plug plug;
 	int ret;

 	blk_start_plug(&plug);
 	ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, page,
 			&bio);
 	if (ret == 0 && bio) {
 		ret = submit_bio_wait(bio);
 		bio_put(bio);
 	}
 	blk_finish_plug(&plug);
 	return ret;
 }
 EXPORT_SYMBOL(blkdev_issue_write_same);

 static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
 		struct bio **biop, unsigned flags)
 {
 	struct bio *bio = *biop;
 	unsigned int max_write_zeroes_sectors;
 	struct request_queue *q = bdev_get_queue(bdev);

 	if (!q)
 		return -ENXIO;

 	if (bdev_read_only(bdev))
 		return -EPERM;

 	/* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
 	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);

 	if (max_write_zeroes_sectors == 0)
 		return -EOPNOTSUPP;

 	while (nr_sects) {
 		bio = blk_next_bio(bio, 0, gfp_mask);
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio->bi_opf = REQ_OP_WRITE_ZEROES;
 		if (flags & BLKDEV_ZERO_NOUNMAP)
 			bio->bi_opf |= REQ_NOUNMAP;

 		if (nr_sects > max_write_zeroes_sectors) {
 			bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
 			nr_sects -= max_write_zeroes_sectors;
 			sector += max_write_zeroes_sectors;
 		} else {
 			bio->bi_iter.bi_size = nr_sects << 9;
 			nr_sects = 0;
 		}
 		cond_resched();
 	}

 	*biop = bio;
 	return 0;
 }

 /*
  * Convert a number of 512B sectors to a number of pages.
  * The result is limited to a number of pages that can fit into a BIO.
  * Also make sure that the result is always at least 1 (page) for the cases
  * where nr_sects is lower than the number of sectors in a page.
  */
 static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
 {
 	sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512);

 	return min(pages, (sector_t)BIO_MAX_PAGES);
 }

 static int __blkdev_issue_zero_pages(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
 		struct bio **biop)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 	struct bio *bio = *biop;
 	int bi_size = 0;
 	unsigned int sz;

 	if (!q)
 		return -ENXIO;

 	if (bdev_read_only(bdev))
 		return -EPERM;

 	while (nr_sects != 0) {
 		bio = blk_next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
 				   gfp_mask);
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);

 		while (nr_sects != 0) {
 			sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
 			bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
 			nr_sects -= bi_size >> 9;
 			sector += bi_size >> 9;
 			if (bi_size < sz)
 				break;
 		}
 		cond_resched();
 	}

 	*biop = bio;
 	return 0;
 }

 /**
  * __blkdev_issue_zeroout - generate number of zero filed write bios
  * @bdev:	blockdev to issue
  * @sector:	start sector
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @biop:	pointer to anchor bio
  * @flags:	controls detailed behavior
  *
  * Description:
  *  Zero-fill a block range, either using hardware offload or by explicitly
  *  writing zeroes to the device.
  *
  *  If a device is using logical block provisioning, the underlying space will
  *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
  *
  *  If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
  *  -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
  */
 int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
 		unsigned flags)
 {
 	int ret;
 	sector_t bs_mask;

 	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
 	if ((sector | nr_sects) & bs_mask)
 		return -EINVAL;

 	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
 			biop, flags);
 	if (ret != -EOPNOTSUPP || (flags & BLKDEV_ZERO_NOFALLBACK))
 		return ret;

 	return __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
 					 biop);
 }
 EXPORT_SYMBOL(__blkdev_issue_zeroout);

 /**
  * blkdev_issue_zeroout - zero-fill a block range
  * @bdev:	blockdev to write
  * @sector:	start sector
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @flags:	controls detailed behavior
  *
  * Description:
  *  Zero-fill a block range, either using hardware offload or by explicitly
  *  writing zeroes to the device.  See __blkdev_issue_zeroout() for the
  *  valid values for %flags.
  */
 int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
 {
 	int ret = 0;
 	sector_t bs_mask;
 	struct bio *bio;
 	struct blk_plug plug;
 	bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);

 	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
 	if ((sector | nr_sects) & bs_mask)
 		return -EINVAL;

 retry:
 	bio = NULL;
 	blk_start_plug(&plug);
 	if (try_write_zeroes) {
 		ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
 						  gfp_mask, &bio, flags);
 	} else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
 		ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
 						gfp_mask, &bio);
 	} else {
 		/* No zeroing offload support */
 		ret = -EOPNOTSUPP;
 	}
 	if (ret == 0 && bio) {
 		ret = submit_bio_wait(bio);
 		bio_put(bio);
 	}
 	blk_finish_plug(&plug);
 	if (ret && try_write_zeroes) {
 		if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
 			try_write_zeroes = false;
 			goto retry;
 		}
 		if (!bdev_write_zeroes_sectors(bdev)) {
 			/*
 			 * Zeroing offload support was indicated, but the
 			 * device reported ILLEGAL REQUEST (for some devices
 			 * there is no non-destructive way to verify whether
 			 * WRITE ZEROES is actually supported).
 			 */
 			ret = -EOPNOTSUPP;
 		}
 	}

 	return ret;
 }
 EXPORT_SYMBOL(blkdev_issue_zeroout);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Functions related to generic helpers functions
	*/
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/bio.h>
	#include <linux/blkdev.h>
	#include <linux/scatterlist.h>

	#include "blk.h"

	struct bio blk_next_bio(struct bio bio, unsigned int nr_pages, gfp_t gfp)
	{
	struct bio *new = bio_alloc(gfp, nr_pages);

	if (bio) {
	bio_chain(bio, new);
	submit_bio(bio);
	}

	return new;
	}

	int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask, int flags,
	struct bio **biop)
	{
	struct request_queue *q = bdev_get_queue(bdev);
	struct bio bio = biop;
	unsigned int op;
	sector_t bs_mask, part_offset = 0;

	if (!q)
	return -ENXIO;

	if (bdev_read_only(bdev))
	return -EPERM;

	if (flags & BLKDEV_DISCARD_SECURE) {
	if (!blk_queue_secure_erase(q))
	return -EOPNOTSUPP;
	op = REQ_OP_SECURE_ERASE;
	} else {
	if (!blk_queue_discard(q))
	return -EOPNOTSUPP;
	op = REQ_OP_DISCARD;
	}

	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	if ((sector \| nr_sects) & bs_mask)
	return -EINVAL;

	if (!nr_sects)
	return -EINVAL;

	/* In case the discard request is in a partition */
	if (bdev->bd_partno)
	part_offset = bdev->bd_part->start_sect;

	while (nr_sects) {
	sector_t granularity_aligned_lba, req_sects;
	sector_t sector_mapped = sector + part_offset;

	granularity_aligned_lba = round_up(sector_mapped,
	q->limits.discard_granularity >> SECTOR_SHIFT);

	/*
	* Check whether the discard bio starts at a discard_granularity
	* aligned LBA,
	* - If no: set (granularity_aligned_lba - sector_mapped) to
	* bi_size of the first split bio, then the second bio will
	* start at a discard_granularity aligned LBA on the device.
	* - If yes: use bio_aligned_discard_max_sectors() as the max
	* possible bi_size of the first split bio. Then when this bio
	* is split in device drive, the split ones are very probably
	* to be aligned to discard_granularity of the device's queue.
	*/
	if (granularity_aligned_lba == sector_mapped)
	req_sects = min_t(sector_t, nr_sects,
	bio_aligned_discard_max_sectors(q));
	else
	req_sects = min_t(sector_t, nr_sects,
	granularity_aligned_lba - sector_mapped);

	WARN_ON_ONCE((req_sects << 9) > UINT_MAX);

	bio = blk_next_bio(bio, 0, gfp_mask);
	bio->bi_iter.bi_sector = sector;
	bio_set_dev(bio, bdev);
	bio_set_op_attrs(bio, op, 0);

	bio->bi_iter.bi_size = req_sects << 9;
	sector += req_sects;
	nr_sects -= req_sects;

	/*
	* We can loop for a long time in here, if someone does
	* full device discards (like mkfs). Be nice and allow
	* us to schedule out to avoid softlocking if preempt
	* is disabled.
	*/
	cond_resched();
	}

	*biop = bio;
	return 0;
	}
	EXPORT_SYMBOL(__blkdev_issue_discard);

	/**
	* blkdev_issue_discard - queue a discard
	* @bdev: blockdev to issue discard for
	* @sector: start sector
	* @nr_sects: number of sectors to discard
	* @gfp_mask: memory allocation flags (for bio_alloc)
	* @flags: BLKDEV_DISCARD_* flags to control behaviour
	*
	* Description:
	* Issue a discard request for the sectors in question.
	*/
	int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
	{
	struct bio *bio = NULL;
	struct blk_plug plug;
	int ret;

	blk_start_plug(&plug);
	ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,
	&bio);
	if (!ret && bio) {
	ret = submit_bio_wait(bio);
	if (ret == -EOPNOTSUPP)
	ret = 0;
	bio_put(bio);
	}
	blk_finish_plug(&plug);

	return ret;
	}
	EXPORT_SYMBOL(blkdev_issue_discard);

	/**
	* __blkdev_issue_write_same - generate number of bios with same page
	* @bdev: target blockdev
	* @sector: start sector
	* @nr_sects: number of sectors to write
	* @gfp_mask: memory allocation flags (for bio_alloc)
	* @page: page containing data to write
	* @biop: pointer to anchor bio
	*
	* Description:
	* Generate and issue number of bios(REQ_OP_WRITE_SAME) with same page.
	*/
	static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask, struct page *page,
	struct bio **biop)
	{
	struct request_queue *q = bdev_get_queue(bdev);
	unsigned int max_write_same_sectors;
	struct bio bio = biop;
	sector_t bs_mask;

	if (!q)
	return -ENXIO;

	if (bdev_read_only(bdev))
	return -EPERM;

	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	if ((sector \| nr_sects) & bs_mask)
	return -EINVAL;

	if (!bdev_write_same(bdev))
	return -EOPNOTSUPP;

	/* Ensure that max_write_same_sectors doesn't overflow bi_size */
	max_write_same_sectors = bio_allowed_max_sectors(q);

	while (nr_sects) {
	bio = blk_next_bio(bio, 1, gfp_mask);
	bio->bi_iter.bi_sector = sector;
	bio_set_dev(bio, bdev);
	bio->bi_vcnt = 1;
	bio->bi_io_vec->bv_page = page;
	bio->bi_io_vec->bv_offset = 0;
	bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
	bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);

	if (nr_sects > max_write_same_sectors) {
	bio->bi_iter.bi_size = max_write_same_sectors << 9;
	nr_sects -= max_write_same_sectors;
	sector += max_write_same_sectors;
	} else {
	bio->bi_iter.bi_size = nr_sects << 9;
	nr_sects = 0;
	}
	cond_resched();
	}

	*biop = bio;
	return 0;
	}

	/**
	* blkdev_issue_write_same - queue a write same operation
	* @bdev: target blockdev
	* @sector: start sector
	* @nr_sects: number of sectors to write
	* @gfp_mask: memory allocation flags (for bio_alloc)
	* @page: page containing data
	*
	* Description:
	* Issue a write same request for the sectors in question.
	*/
	int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask,
	struct page *page)
	{
	struct bio *bio = NULL;
	struct blk_plug plug;
	int ret;

	blk_start_plug(&plug);
	ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, page,
	&bio);
	if (ret == 0 && bio) {
	ret = submit_bio_wait(bio);
	bio_put(bio);
	}
	blk_finish_plug(&plug);
	return ret;
	}
	EXPORT_SYMBOL(blkdev_issue_write_same);

	static int __blkdev_issue_write_zeroes(struct block_device *bdev,
	sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
	struct bio **biop, unsigned flags)
	{
	struct bio bio = biop;
	unsigned int max_write_zeroes_sectors;
	struct request_queue *q = bdev_get_queue(bdev);

	if (!q)
	return -ENXIO;

	if (bdev_read_only(bdev))
	return -EPERM;

	/* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);

	if (max_write_zeroes_sectors == 0)
	return -EOPNOTSUPP;

	while (nr_sects) {
	bio = blk_next_bio(bio, 0, gfp_mask);
	bio->bi_iter.bi_sector = sector;
	bio_set_dev(bio, bdev);
	bio->bi_opf = REQ_OP_WRITE_ZEROES;
	if (flags & BLKDEV_ZERO_NOUNMAP)
	bio->bi_opf \|= REQ_NOUNMAP;

	if (nr_sects > max_write_zeroes_sectors) {
	bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
	nr_sects -= max_write_zeroes_sectors;
	sector += max_write_zeroes_sectors;
	} else {
	bio->bi_iter.bi_size = nr_sects << 9;
	nr_sects = 0;
	}
	cond_resched();
	}

	*biop = bio;
	return 0;
	}

	/*
	* Convert a number of 512B sectors to a number of pages.
	* The result is limited to a number of pages that can fit into a BIO.
	* Also make sure that the result is always at least 1 (page) for the cases
	* where nr_sects is lower than the number of sectors in a page.
	*/
	static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
	{
	sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512);

	return min(pages, (sector_t)BIO_MAX_PAGES);
	}

	static int __blkdev_issue_zero_pages(struct block_device *bdev,
	sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
	struct bio **biop)
	{
	struct request_queue *q = bdev_get_queue(bdev);
	struct bio bio = biop;
	int bi_size = 0;
	unsigned int sz;

	if (!q)
	return -ENXIO;

	if (bdev_read_only(bdev))
	return -EPERM;

	while (nr_sects != 0) {
	bio = blk_next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
	gfp_mask);
	bio->bi_iter.bi_sector = sector;
	bio_set_dev(bio, bdev);
	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);

	while (nr_sects != 0) {
	sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
	bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
	nr_sects -= bi_size >> 9;
	sector += bi_size >> 9;
	if (bi_size < sz)
	break;
	}
	cond_resched();
	}

	*biop = bio;
	return 0;
	}

	/**
	* __blkdev_issue_zeroout - generate number of zero filed write bios
	* @bdev: blockdev to issue
	* @sector: start sector
	* @nr_sects: number of sectors to write
	* @gfp_mask: memory allocation flags (for bio_alloc)
	* @biop: pointer to anchor bio
	* @flags: controls detailed behavior
	*
	* Description:
	* Zero-fill a block range, either using hardware offload or by explicitly
	* writing zeroes to the device.
	*
	* If a device is using logical block provisioning, the underlying space will
	* not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
	*
	* If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
	* -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
	*/
	int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
	unsigned flags)
	{
	int ret;
	sector_t bs_mask;

	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	if ((sector \| nr_sects) & bs_mask)
	return -EINVAL;

	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
	biop, flags);
	if (ret != -EOPNOTSUPP \|\| (flags & BLKDEV_ZERO_NOFALLBACK))
	return ret;

	return __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
	biop);
	}
	EXPORT_SYMBOL(__blkdev_issue_zeroout);

	/**
	* blkdev_issue_zeroout - zero-fill a block range
	* @bdev: blockdev to write
	* @sector: start sector
	* @nr_sects: number of sectors to write
	* @gfp_mask: memory allocation flags (for bio_alloc)
	* @flags: controls detailed behavior
	*
	* Description:
	* Zero-fill a block range, either using hardware offload or by explicitly
	* writing zeroes to the device. See __blkdev_issue_zeroout() for the
	* valid values for %flags.
	*/
	int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
	sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
	{
	int ret = 0;
	sector_t bs_mask;
	struct bio *bio;
	struct blk_plug plug;
	bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);

	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	if ((sector \| nr_sects) & bs_mask)
	return -EINVAL;

	retry:
	bio = NULL;
	blk_start_plug(&plug);
	if (try_write_zeroes) {
	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
	gfp_mask, &bio, flags);
	} else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
	ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
	gfp_mask, &bio);
	} else {
	/* No zeroing offload support */
	ret = -EOPNOTSUPP;
	}
	if (ret == 0 && bio) {
	ret = submit_bio_wait(bio);
	bio_put(bio);
	}
	blk_finish_plug(&plug);
	if (ret && try_write_zeroes) {
	if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
	try_write_zeroes = false;
	goto retry;
	}
	if (!bdev_write_zeroes_sectors(bdev)) {
	/*
	* Zeroing offload support was indicated, but the
	* device reported ILLEGAL REQUEST (for some devices
	* there is no non-destructive way to verify whether
	* WRITE ZEROES is actually supported).
	*/
	ret = -EOPNOTSUPP;
	}
	}

	return ret;
	}
	EXPORT_SYMBOL(blkdev_issue_zeroout);