On Wed, Nov 14, 2018 at 08:43:37AM +1100, Dave Chinner wrote: > From: Dave Chinner <[email protected]> > > 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") > Signed-off-by: Dave Chinner <[email protected]>
Fixes the regression for me too, so... Tested-by: Darrick J. Wong <[email protected]> Reviewed-by: Darrick J. Wong <[email protected]> --D > --- > block/blk-lib.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/block/blk-lib.c b/block/blk-lib.c > index e8b3bb9bf375..144e156ed341 100644 > --- a/block/blk-lib.c > +++ b/block/blk-lib.c > @@ -55,9 +55,12 @@ 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 == 0); > + 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); > -- > 2.19.1 >
