[linux-2.6-block.git] / block / blk-lib.c

// 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;
}
EXPORT_SYMBOL_GPL(blk_next_bio);

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;
	}

	/* In case the discard granularity isn't set by buggy device driver */
	if (WARN_ON_ONCE(!q->limits.discard_granularity)) {
		char dev_name[BDEVNAME_SIZE];

		bdevname(bdev, dev_name);
		pr_err_ratelimited("%s: Error: discard_granularity is 0.\n", dev_name);
		return -EOPNOTSUPP;
	}

	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_is_partition(bdev))
		part_offset = bdev->bd_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);

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_VECS);
}

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);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
f31e7e40 DM	2	/*
	3	* Functions related to generic helpers functions
	4	*/
	5	#include <linux/kernel.h>
	6	#include <linux/module.h>
	7	#include <linux/bio.h>
	8	#include <linux/blkdev.h>
	9	#include <linux/scatterlist.h>
	10
	11	#include "blk.h"
	12
a2d6b3a2	13	struct bio blk_next_bio(struct bio bio, unsigned int nr_pages, gfp_t gfp)
f31e7e40	14	{
9082e87b CH	15	struct bio *new = bio_alloc(gfp, nr_pages);
	16
	17	if (bio) {
	18	bio_chain(bio, new);
4e49ea4a	19	submit_bio(bio);
9082e87b	20	}
5dba3089	21
9082e87b	22	return new;
f31e7e40	23	}
c28a6147	24	EXPORT_SYMBOL_GPL(blk_next_bio);
f31e7e40	25
38f25255	26	int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
288dab8a	27	sector_t nr_sects, gfp_t gfp_mask, int flags,
469e3216	28	struct bio **biop)
f31e7e40	29	{
f31e7e40	30	struct request_queue *q = bdev_get_queue(bdev);
38f25255	31	struct bio bio = biop;
ef295ecf	32	unsigned int op;
9b15d109	33	sector_t bs_mask, part_offset = 0;
f31e7e40 DM	34
	35	if (!q)
	36	return -ENXIO;
288dab8a	37
a13553c7 ID	38	if (bdev_read_only(bdev))
	39	return -EPERM;
	40
288dab8a CH	41	if (flags & BLKDEV_DISCARD_SECURE) {
	42	if (!blk_queue_secure_erase(q))
	43	return -EOPNOTSUPP;
	44	op = REQ_OP_SECURE_ERASE;
	45	} else {
	46	if (!blk_queue_discard(q))
	47	return -EOPNOTSUPP;
	48	op = REQ_OP_DISCARD;
	49	}
f31e7e40	50
b35fd742 CL	51	/* In case the discard granularity isn't set by buggy device driver */
	52	if (WARN_ON_ONCE(!q->limits.discard_granularity)) {
	53	char dev_name[BDEVNAME_SIZE];
	54
	55	bdevname(bdev, dev_name);
	56	pr_err_ratelimited("%s: Error: discard_granularity is 0.\n", dev_name);
	57	return -EOPNOTSUPP;
	58	}
	59
28b2be20 DW	60	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	61	if ((sector \| nr_sects) & bs_mask)
	62	return -EINVAL;
	63
ba5d7385 ML	64	if (!nr_sects)
ba5d7385 ML	65	return -EINVAL;
a22c4d7e	66
9b15d109	67	/* In case the discard request is in a partition */
fa01b1e9	68	if (bdev_is_partition(bdev))
29ff57c6	69	part_offset = bdev->bd_start_sect;
9b15d109	70
ba5d7385	71	while (nr_sects) {
9b15d109 CL	72	sector_t granularity_aligned_lba, req_sects;
	73	sector_t sector_mapped = sector + part_offset;
	74
	75	granularity_aligned_lba = round_up(sector_mapped,
	76	q->limits.discard_granularity >> SECTOR_SHIFT);
	77
	78	/*
	79	* Check whether the discard bio starts at a discard_granularity
	80	* aligned LBA,
	81	* - If no: set (granularity_aligned_lba - sector_mapped) to
	82	* bi_size of the first split bio, then the second bio will
	83	* start at a discard_granularity aligned LBA on the device.
	84	* - If yes: use bio_aligned_discard_max_sectors() as the max
	85	* possible bi_size of the first split bio. Then when this bio
	86	* is split in device drive, the split ones are very probably
	87	* to be aligned to discard_granularity of the device's queue.
	88	*/
	89	if (granularity_aligned_lba == sector_mapped)
	90	req_sects = min_t(sector_t, nr_sects,
	91	bio_aligned_discard_max_sectors(q));
	92	else
	93	req_sects = min_t(sector_t, nr_sects,
	94	granularity_aligned_lba - sector_mapped);
c6e66634	95
4800bf7b DC	96	WARN_ON_ONCE((req_sects << 9) > UINT_MAX);
4800bf7b DC	97
a2d6b3a2	98	bio = blk_next_bio(bio, 0, gfp_mask);
4f024f37	99	bio->bi_iter.bi_sector = sector;
74d46992	100	bio_set_dev(bio, bdev);
288dab8a	101	bio_set_op_attrs(bio, op, 0);
f31e7e40	102
4f024f37	103	bio->bi_iter.bi_size = req_sects << 9;
ba5d7385	104	sector += req_sects;
c6e66634	105	nr_sects -= req_sects;
f31e7e40	106
c8123f8c JA	107	/*
	108	* We can loop for a long time in here, if someone does
	109	* full device discards (like mkfs). Be nice and allow
	110	* us to schedule out to avoid softlocking if preempt
	111	* is disabled.
	112	*/
	113	cond_resched();
5dba3089	114	}
38f25255 CH	115
	116	*biop = bio;
	117	return 0;
	118	}
	119	EXPORT_SYMBOL(__blkdev_issue_discard);
	120
	121	/**
	122	* blkdev_issue_discard - queue a discard
	123	* @bdev: blockdev to issue discard for
	124	* @sector: start sector
	125	* @nr_sects: number of sectors to discard
	126	* @gfp_mask: memory allocation flags (for bio_alloc)
e554911c	127	* @flags: BLKDEV_DISCARD_* flags to control behaviour
38f25255 CH	128	*
	129	* Description:
	130	* Issue a discard request for the sectors in question.
	131	*/
	132	int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
	133	sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
	134	{
38f25255 CH	135	struct bio *bio = NULL;
	136	struct blk_plug plug;
	137	int ret;
	138
38f25255	139	blk_start_plug(&plug);
288dab8a	140	ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,
38f25255	141	&bio);
bbd848e0	142	if (!ret && bio) {
4e49ea4a	143	ret = submit_bio_wait(bio);
48920ff2	144	if (ret == -EOPNOTSUPP)
bbd848e0	145	ret = 0;
05bd92dd	146	bio_put(bio);
bbd848e0	147	}
0cfbcafc	148	blk_finish_plug(&plug);
f31e7e40	149
bbd848e0	150	return ret;
f31e7e40 DM	151	}
f31e7e40 DM	152	EXPORT_SYMBOL(blkdev_issue_discard);
3f14d792	153
a6f0788e CK	154	static int __blkdev_issue_write_zeroes(struct block_device *bdev,
a6f0788e CK	155	sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
d928be9f	156	struct bio **biop, unsigned flags)
a6f0788e CK	157	{
	158	struct bio bio = biop;
	159	unsigned int max_write_zeroes_sectors;
	160	struct request_queue *q = bdev_get_queue(bdev);
	161
	162	if (!q)
	163	return -ENXIO;
	164
a13553c7 ID	165	if (bdev_read_only(bdev))
	166	return -EPERM;
	167
a6f0788e CK	168	/* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
	169	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);
	170
	171	if (max_write_zeroes_sectors == 0)
	172	return -EOPNOTSUPP;
	173
	174	while (nr_sects) {
a2d6b3a2	175	bio = blk_next_bio(bio, 0, gfp_mask);
a6f0788e	176	bio->bi_iter.bi_sector = sector;
74d46992	177	bio_set_dev(bio, bdev);
d928be9f CH	178	bio->bi_opf = REQ_OP_WRITE_ZEROES;
	179	if (flags & BLKDEV_ZERO_NOUNMAP)
	180	bio->bi_opf \|= REQ_NOUNMAP;
a6f0788e CK	181
	182	if (nr_sects > max_write_zeroes_sectors) {
	183	bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
	184	nr_sects -= max_write_zeroes_sectors;
	185	sector += max_write_zeroes_sectors;
	186	} else {
	187	bio->bi_iter.bi_size = nr_sects << 9;
	188	nr_sects = 0;
	189	}
	190	cond_resched();
	191	}
	192
	193	*biop = bio;
	194	return 0;
	195	}
	196
615d22a5 DLM	197	/*
	198	* Convert a number of 512B sectors to a number of pages.
	199	* The result is limited to a number of pages that can fit into a BIO.
	200	* Also make sure that the result is always at least 1 (page) for the cases
	201	* where nr_sects is lower than the number of sectors in a page.
	202	*/
	203	static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
	204	{
09c2c359	205	sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512);
615d22a5	206
a8affc03	207	return min(pages, (sector_t)BIO_MAX_VECS);
615d22a5 DLM	208	}
615d22a5 DLM	209
425a4dba ID	210	static int __blkdev_issue_zero_pages(struct block_device *bdev,
	211	sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
	212	struct bio **biop)
	213	{
	214	struct request_queue *q = bdev_get_queue(bdev);
	215	struct bio bio = biop;
	216	int bi_size = 0;
	217	unsigned int sz;
	218
	219	if (!q)
	220	return -ENXIO;
	221
a13553c7 ID	222	if (bdev_read_only(bdev))
	223	return -EPERM;
	224
425a4dba	225	while (nr_sects != 0) {
a2d6b3a2 DLM	226	bio = blk_next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
a2d6b3a2 DLM	227	gfp_mask);
425a4dba ID	228	bio->bi_iter.bi_sector = sector;
	229	bio_set_dev(bio, bdev);
	230	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
	231
	232	while (nr_sects != 0) {
	233	sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
	234	bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
	235	nr_sects -= bi_size >> 9;
	236	sector += bi_size >> 9;
	237	if (bi_size < sz)
	238	break;
	239	}
	240	cond_resched();
	241	}
	242
	243	*biop = bio;
	244	return 0;
	245	}
	246
3f14d792	247	/**
e73c23ff	248	* __blkdev_issue_zeroout - generate number of zero filed write bios
3f14d792 DM	249	* @bdev: blockdev to issue
	250	* @sector: start sector
	251	* @nr_sects: number of sectors to write
	252	* @gfp_mask: memory allocation flags (for bio_alloc)
e73c23ff	253	* @biop: pointer to anchor bio
ee472d83	254	* @flags: controls detailed behavior
3f14d792 DM	255	*
3f14d792 DM	256	* Description:
ee472d83 CH	257	* Zero-fill a block range, either using hardware offload or by explicitly
	258	* writing zeroes to the device.
	259	*
	260	* If a device is using logical block provisioning, the underlying space will
	261	* not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
cb365b96 CH	262	*
	263	* If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
	264	* -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
3f14d792	265	*/
e73c23ff CK	266	int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
e73c23ff CK	267	sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
ee472d83	268	unsigned flags)
3f14d792	269	{
18edc8ea	270	int ret;
28b2be20 DW	271	sector_t bs_mask;
	272
	273	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	274	if ((sector \| nr_sects) & bs_mask)
	275	return -EINVAL;
3f14d792	276
a6f0788e	277	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
d928be9f	278	biop, flags);
cb365b96	279	if (ret != -EOPNOTSUPP \|\| (flags & BLKDEV_ZERO_NOFALLBACK))
425a4dba	280	return ret;
3f14d792	281
425a4dba ID	282	return __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
425a4dba ID	283	biop);
3f14d792	284	}
e73c23ff	285	EXPORT_SYMBOL(__blkdev_issue_zeroout);
579e8f3c MP	286
	287	/**
	288	* blkdev_issue_zeroout - zero-fill a block range
	289	* @bdev: blockdev to write
	290	* @sector: start sector
	291	* @nr_sects: number of sectors to write
	292	* @gfp_mask: memory allocation flags (for bio_alloc)
ee472d83	293	* @flags: controls detailed behavior
579e8f3c MP	294	*
579e8f3c MP	295	* Description:
ee472d83 CH	296	* Zero-fill a block range, either using hardware offload or by explicitly
	297	* writing zeroes to the device. See __blkdev_issue_zeroout() for the
	298	* valid values for %flags.
579e8f3c	299	*/
579e8f3c	300	int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
ee472d83	301	sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
579e8f3c	302	{
d5ce4c31 ID	303	int ret = 0;
	304	sector_t bs_mask;
	305	struct bio *bio;
e73c23ff	306	struct blk_plug plug;
d5ce4c31	307	bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);
d93ba7a5	308
d5ce4c31 ID	309	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
	310	if ((sector \| nr_sects) & bs_mask)
	311	return -EINVAL;
	312
	313	retry:
	314	bio = NULL;
e73c23ff	315	blk_start_plug(&plug);
d5ce4c31 ID	316	if (try_write_zeroes) {
	317	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
	318	gfp_mask, &bio, flags);
	319	} else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
	320	ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
	321	gfp_mask, &bio);
	322	} else {
	323	/* No zeroing offload support */
	324	ret = -EOPNOTSUPP;
	325	}
e73c23ff CK	326	if (ret == 0 && bio) {
	327	ret = submit_bio_wait(bio);
	328	bio_put(bio);
	329	}
	330	blk_finish_plug(&plug);
d5ce4c31 ID	331	if (ret && try_write_zeroes) {
	332	if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
	333	try_write_zeroes = false;
	334	goto retry;
	335	}
	336	if (!bdev_write_zeroes_sectors(bdev)) {
	337	/*
	338	* Zeroing offload support was indicated, but the
	339	* device reported ILLEGAL REQUEST (for some devices
	340	* there is no non-destructive way to verify whether
	341	* WRITE ZEROES is actually supported).
	342	*/
	343	ret = -EOPNOTSUPP;
	344	}
	345	}
579e8f3c	346
e73c23ff	347	return ret;
579e8f3c	348	}
3f14d792	349	EXPORT_SYMBOL(blkdev_issue_zeroout);