Commit 64b582ca authored by John Garry's avatar John Garry Committed by Jens Axboe
Browse files

block: Read max write zeroes once for __blkdev_issue_write_zeroes() 

As reported in [0], we may get a hang when formatting a XFS FS on a RAID0
drive.

Commit 73a768d5 ("block: factor out a blk_write_zeroes_limit helper")
changed __blkdev_issue_write_zeroes() to read the max write zeroes
value in the loop. This is not safe as max write zeroes may change in
value. Specifically for the case of [0], the value goes to 0, and we get
an infinite loop.

Lift the limit reading out of the loop.

[0] https://lore.kernel.org/linux-xfs/4d31268f-310b-4220-88a2-e191c3932a82@oracle.com/T/#t



Fixes: 73a768d5 ("block: factor out a blk_write_zeroes_limit helper")
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJohn Garry <john.g.garry@oracle.com>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240815163228.216051-2-john.g.garry@oracle.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b313a8c8

block/blk-lib.c

+18 −7
Original line number Diff line number Diff line
@@ -111,13 +111,20 @@ static sector_t bio_write_zeroes_limit(struct block_device *bdev) 
		(UINT_MAX >> SECTOR_SHIFT) & ~bs_mask);

}



/*

 * There is no reliable way for the SCSI subsystem to determine whether a

 * device supports a WRITE SAME operation without actually performing a write

 * to media. As a result, write_zeroes is enabled by default and will be

 * disabled if a zeroing operation subsequently fails. This means that this

 * queue limit is likely to change at runtime.

 */

static void __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 **biop, unsigned flags, sector_t limit)

{



	while (nr_sects) {

		unsigned int len = min_t(sector_t, nr_sects,

				bio_write_zeroes_limit(bdev));

		unsigned int len = min(nr_sects, limit);

		struct bio *bio;



		if ((flags & BLKDEV_ZERO_KILLABLE) &&
@@ -141,12 +148,14 @@ static void __blkdev_issue_write_zeroes(struct block_device *bdev, 
static int blkdev_issue_write_zeroes(struct block_device *bdev, sector_t sector,

		sector_t nr_sects, gfp_t gfp, unsigned flags)

{

	sector_t limit = bio_write_zeroes_limit(bdev);

	struct bio *bio = NULL;

	struct blk_plug plug;

	int ret = 0;



	blk_start_plug(&plug);

	__blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, &bio, flags);

	__blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, &bio,

			flags, limit);

	if (bio) {

		if ((flags & BLKDEV_ZERO_KILLABLE) &&

		    fatal_signal_pending(current)) {
@@ -165,7 +174,7 @@ static int blkdev_issue_write_zeroes(struct block_device *bdev, sector_t sector, 
	 * on an I/O error, in which case we'll turn any error into

	 * "not supported" here.

	 */

	if (ret && !bdev_write_zeroes_sectors(bdev))

	if (ret && !limit)

		return -EOPNOTSUPP;

	return ret;

}
@@ -265,12 +274,14 @@ int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, 
		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,

		unsigned flags)

{

	sector_t limit = bio_write_zeroes_limit(bdev);



	if (bdev_read_only(bdev))

		return -EPERM;



	if (bdev_write_zeroes_sectors(bdev)) {

	if (limit) {

		__blkdev_issue_write_zeroes(bdev, sector, nr_sects,

				gfp_mask, biop, flags);

				gfp_mask, biop, flags, limit);

	} else {

		if (flags & BLKDEV_ZERO_NOFALLBACK)

			return -EOPNOTSUPP;