[PATCH v2 1/2] block: Read max write zeroes once for __blkdev_issue_write_zeroes()
From: John Garry <john.g.garry@oracle.com>
Date: 2024-08-15 16:32:54
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
As reported in [0], we may get a hang when formatting a XFS FS on a RAID0
drive.
Commit 73a768d5f955 ("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 (local)
Fixes: 73a768d5f955 ("block: factor out a blk_write_zeroes_limit helper")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
block/blk-lib.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 9f735efa6c94..83eb7761c2bf 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c@@ -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;
--
2.31.1