From: Ming Lei ming.lei@redhat.com
Commit ba5d73851e71847ba7f7f4c27a1a6e1f5ab91c79 upstream.
Cleanup __blkdev_issue_discard() a bit:
- remove local variable of 'end_sect' - remove code block of 'fail'
Cc: Mike Snitzer snitzer@redhat.com Cc: Christoph Hellwig hch@lst.de Cc: Xiao Ni xni@redhat.com Cc: Mariusz Dabrowski mariusz.dabrowski@intel.com Tested-by: Rui Salvaterra rsalvaterra@gmail.com Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru --- block/blk-lib.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c index 1f196cf0aa5d..41088d5466c1 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -52,15 +52,12 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, if ((sector | nr_sects) & bs_mask) return -EINVAL;
- while (nr_sects) { - unsigned int req_sects = nr_sects; - sector_t end_sect; - - if (!req_sects) - goto fail; - req_sects = min(req_sects, bio_allowed_max_sectors(q)); + if (!nr_sects) + return -EINVAL;
- end_sect = sector + req_sects; + while (nr_sects) { + unsigned int req_sects = min_t(unsigned int, nr_sects, + bio_allowed_max_sectors(q));
bio = next_bio(bio, 0, gfp_mask); bio->bi_iter.bi_sector = sector; @@ -68,8 +65,8 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, bio_set_op_attrs(bio, op, 0);
bio->bi_iter.bi_size = req_sects << 9; + sector += req_sects; nr_sects -= req_sects; - sector = end_sect;
/* * We can loop for a long time in here, if someone does @@ -82,14 +79,6 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
*biop = bio; return 0; - -fail: - if (bio) { - submit_bio_wait(bio); - bio_put(bio); - } - *biop = NULL; - return -EOPNOTSUPP; } EXPORT_SYMBOL(__blkdev_issue_discard);
From: Dave Chinner dchinner@redhat.com
Commit 4800bf7bc8c725e955fcbc6191cc872f43f506d3 upstream.
-- snip --
Overflow in __blkdev_issue_discard() actually exists since 4.18 commit af097f5d199e2aa3ab3ef777f0716e487b8f7b08 ("block: break discard submissions into the user defined size"):
- req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9); + req_sects = min_t(sector_t, nr_sects, q->limits.max_discard_sectors)
Default max_discard_sectors could be bigger than UINT_MAX.
And finally 4.19 commit 744889b7cbb56a64f957e65ade7cb65fe3f35714 ("block: don't deal with discard limit in blkdev_issue_discard()") made problem worse:
- req_sects = min_t(sector_t, nr_sects, q->limits.max_discard_sectors); + req_sects = nr_sects;
Now BLKDISCARD ioctl fails unexpectedly if lower word of length is zero: ioctl(3, BLKDISCARD, [0, 0x20000000000]) = -1 EOPNOTSUPP (Operation not supported)
-- snip --
A discard cleanup merged into 4.20-rc2 causes fstests xfs/259 to fall into an endless loop in the discard code. The test is creating a device that is exactly 2^32 sectors in size to test mkfs boundary conditions around the 32 bit sector overflow region.
mkfs issues a discard for the entire device size by default, and hence this throws a sector count of 2^32 into blkdev_issue_discard(). It takes the number of sectors to discard as a sector_t - a 64 bit value.
The commit ba5d73851e71 ("block: cleanup __blkdev_issue_discard") takes this sector count and casts it to a 32 bit value before comapring it against the maximum allowed discard size the device has. This truncates away the upper 32 bits, and so if the lower 32 bits of the sector count is zero, it starts issuing discards of length 0. This causes the code to fall into an endless loop, issuing a zero length discards over and over again on the same sector.
Fixes: ba5d73851e71 ("block: cleanup __blkdev_issue_discard") Tested-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Dave Chinner dchinner@redhat.com
Killed pointless WARN_ON().
Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru --- block/blk-lib.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c index 41088d5466c1..0dbc9e2ab9a3 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -56,9 +56,11 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, return -EINVAL;
while (nr_sects) { - unsigned int req_sects = min_t(unsigned int, nr_sects, + sector_t req_sects = min_t(sector_t, nr_sects, bio_allowed_max_sectors(q));
+ WARN_ON_ONCE((req_sects << 9) > UINT_MAX); + bio = next_bio(bio, 0, gfp_mask); bio->bi_iter.bi_sector = sector; bio_set_dev(bio, bdev);
linux-stable-mirror@lists.linaro.org
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Konstantin Khlebnikov