Jens Axboe <ax...@kernel.dk> writes: > On 2012-09-28 08:09, Dave Chinner wrote: >> From: Dave Chinner <dchin...@redhat.com> >> >> xfstests has always had random failures of tests due to loop devices >> failing to be torn down and hence leaving filesytems that cannot be >> unmounted. This causes test runs to immediately stop. >> >> Over the past 6 or 7 years we've added hacks like explicit unmount >> -d commands for loop mounts, losetup -d after unmount -d fails, etc, >> but still the problems persist. Recently, the frequency of loop >> related failures increased again to the point that xfstests 259 will >> reliably fail with a stray loop device that was not torn down. >> >> That is despite the fact the test is above as simple as it gets - >> loop 5 or 6 times running mkfs.xfs with different paramters: >> >> lofile=$(losetup -f) >> losetup $lofile "$testfile" >> "$MKFS_XFS_PROG" -b size=512 $lofile >/dev/null || echo "mkfs >> failed!" >> sync >> losetup -d $lofile >> >> And losteup -d $lofile is failing with EBUSY on 1-3 of these loops >> every time the test is run. >> >> Turns out that blkid is running simultaneously with losetup -d, and >> so it sees an elevated reference count and returns EBUSY. But why >> is blkid running? It's obvious, isn't it? udev has decided to try >> and find out what is on the block device as a result of a creation >> notification. And it is racing with mkfs, so might still be scanning >> the device when mkfs finishes and we try to tear it down. >> >> So, make losetup -d force autoremove behaviour. That is, when the >> last reference goes away, tear down the device. xfstests wants it >> *gone*, not causing random teardown failures when we know that all >> the operations the tests have specifically run on the device have >> completed and are no longer referencing the loop device. > > I hear that %^#@#! blkid behavior, it is such a pain in the neck. I > don't know how many times I've had to explain that behaviour to people > who run write testing with tracing, wonder wtf there are reads in the > trace. > > Patch looks fine, seems like the sane thing to do (lazy-remove on last > drop) for this case.
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