On 11/13/18 2:43 PM, 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.
Applied, thanks. Ming, can you please add a blktests test for this case? This is the 2nd time it's been broken. -- Jens Axboe
