From: Dave Chinner dchinner@redhat.com
commit 4800bf7bc8c725e955fcbc6191cc872f43f506d3 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- block/blk-lib.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -56,9 +56,11 @@ int __blkdev_issue_discard(struct block_ 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);