On 22/04/04 09:28AM, Dave Chinner wrote: > On Thu, Mar 31, 2022 at 06:24:20PM +0530, Ritesh Harjani wrote: > > From: Ritesh Harjani <riteshh@xxxxxxxxxxxxx> > > > > Add another falloc test entry which could hit a kernel bug > > with ext4 fast_commit feature w/o below kernel commit [1]. > > > > <log> > > [ 410.888496][ T2743] BUG: KASAN: use-after-free in ext4_mb_mark_bb+0x26a/0x6c0 > > [ 410.890432][ T2743] Read of size 8 at addr ffff888171886000 by task mount/2743 > > > > This happens when falloc -k size is huge which spans across more than > > 1 flex block group in ext4. This causes a bug in fast_commit replay > > code which is fixed by kernel commit at [1]. > > > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=bfdc502a4a4c058bf4cbb1df0c297761d528f54d > > > > Signed-off-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx> > > --- > > tests/generic/468 | 8 ++++++++ > > tests/generic/468.out | 2 ++ > > 2 files changed, 10 insertions(+) > > > > diff --git a/tests/generic/468 b/tests/generic/468 > > index 95752d3b..5e73cff9 100755 > > --- a/tests/generic/468 > > +++ b/tests/generic/468 > > @@ -34,6 +34,13 @@ _scratch_mkfs >/dev/null 2>&1 > > _require_metadata_journaling $SCRATCH_DEV > > _scratch_mount > > > > +# blocksize and fact are used in the last case of the fsync/fdatasync test. > > +# This is mainly trying to test recovery operation in case where the data > > +# blocks written, exceeds the default flex group size (32768*4096*16) in ext4. > > +blocks=32768 > > +blocksize=4096 > > Block size can change based on mkfs parameters. You should extract > this dynamically from the filesystem the test is being run on. > Yes, but we still have kept just 4096 because, anything bigger than that like 65536 might require a bigger disk size itself to test. The overall size requirement of the disk will then become ~36G (32768 * 65536 * 18) Hence I went ahead with 4096 which is good enough for testing. But sure, I will add a comment explaining why we have hardcoded it to 4096 so that others don't get confused. Larger than this size disk anyway doesn't get tested much right? > > +fact=18 > > What is "fact" supposed to mean? > > Indeed, wouldn't this simply be better as something like: > > larger_than_ext4_fg_size=$((32768 * $blksize * 18)) > > And then > > > testfile=$SCRATCH_MNT/testfile > > > > # check inode metadata after shutdown > > @@ -85,6 +92,7 @@ for i in fsync fdatasync; do > > test_falloc $i "-k " 1024 > > test_falloc $i "-k " 4096 > > test_falloc $i "-k " 104857600 > > + test_falloc $i "-k " $(($blocks*$blocksize*$fact)) > > test_falloc $i "-k " $larger_than_ext4_fg_size > Yes, looks good to me. Thanks for suggestion. > And just scrub all the sizes from the golden output? > This won't be needed since I still would like to go with 4096 blocksize, to avoid a large disk size requirement which anyway won't be tested much. If this sounds good to you, I will fix rest of the changes as discussed in the next revision. -ritesh
