Re: [PATCH] xfs: test agfl reset on bad list wrapping

Brian Foster
2018-03-20T10:39:01Z

On Mon, Mar 19, 2018 at 05:08:42PM -0700, Darrick J. Wong wrote:
> On Mon, Mar 19, 2018 at 01:34:47PM -0400, Brian Foster wrote:
> > On Fri, Mar 16, 2018 at 09:26:02AM -0700, Darrick J. Wong wrote:
...
> > The test fails for me on a kernel with the agfl reset patch:
> >
> > # diff -u tests/xfs/709.out /root/xfstests-dev/results//xfs/709.out.bad
> > --- tests/xfs/709.out 2018-03-19 12:05:20.146356068 -0400
> > +++ /root/xfstests-dev/results//xfs/709.out.bad 2018-03-19
> > 12:32:01.722735121 -0400
> > @@ -7,6 +7,16 @@
> > TEST good_start
> > TEST good_wrap
> > TEST bad_start
> > +/mnt/scratch/a: Input/output error
> > +Error: AG 0 free space header: Repairs are required.
> > +Error: AG 0 free list: Repairs are required.
> > +Error: AG 0 freesp by block btree: Repairs are required.
> > +Error: AG 0 freesp by length btree: Repairs are required.
> > +Error: AG 0 inode btree: Repairs are required.
> > +Error: AG 0 free inode btree: Repairs are required.
> > +Error: dev 253:3 AG 0 fsmap: Structure needs cleaning.
> > +/mnt/scratch: errors found: 7
> > +/mnt/scratch: Unmount and run xfs_repair.
> > expected flfirst < good_agfl_size - 1
> > expected flfirst < fllast
> > TEST no_move
> >
> > I think the errors are expected in this case, but the test probably
> > shouldn't fail..? (FYI, I didn't have CONFIG_XFS_DEBUG enabled at first.
> > I tried it again with CONFIG_XFS_DEBUG=y and the test passes.)
>
> Hm, that's fun. :)
>
> What kernel, xfsprogs, etc.?
>

Heh. That was latest for-next (+ agfl reset) and
xfsprogs-4.15.1-1.fc29.x86_64 (rawhide).

> Or maybe it's easier just to remove the scrub parts until I get that
> part settled down since in theory the agfl scrubber could just detect
> the alignment error and return failure immediately.
>
...
> > > diff --git a/tests/xfs/709 b/tests/xfs/709
> > > new file mode 100755
> > > index 0000000..832a469
> > > --- /dev/null
> > > +++ b/tests/xfs/709
> > > @@ -0,0 +1,260 @@
...
> > > +
> > > +# get standard environment, filters and checks
> > > +. ./common/rc
> > > +. ./common/xfs
> > > +. ./common/filter
> > > +. ./common/populate
> > > +
> >
> > Do we need the xfs and populate includes?
>
> common/populate has the helpers for getting/setting metadata object fields.
>

Which ones? The test runs fine for me w/o that included.

> common/xfs has _require_scratch_xfs_crc
>

I see Eryu already addressed this... the rest of the feedback sounds
good.

Brian

> > > +# real QA test starts here
> > > +_supported_fs xfs
> > > +_supported_os Linux
> > > +
> > > +_require_freeze
> >
> > Or this?
>
> Yeah that can go away.
>
> > > +_require_scratch_nocheck
> > > +_require_test_program "punch-alternating"
> > > +
> > > +# This is only a v5 filesystem problem
> > > +_require_scratch_xfs_crc
> > > +
> > > +mount_loop() {
> > > + if ! _try_scratch_mount >> $seqres.full 2>&1; then
> > > + echo "scratch mount failed" >> $seqres.full
> > > + return
> > > + fi
> > > +
> > > + # Trigger agfl fixing by fragmenting free space
> > > + rm -rf $SCRATCH_MNT/a
> > > + dd if=/dev/zero of=$SCRATCH_MNT/a bs=8192k >> $seqres.full 2>&1
> >
> > I guess we aren't really writing a lot, but fallocate might be more
> > efficient...
> >
> > > + ./src/punch-alternating $SCRATCH_MNT/a
> > > + sync
> >
> > ... and perhaps fsync.
>
> Heh, I could skip this entirely since punch-alternating does the
> fsync for us already.
>
> > > + rm -rf $SCRATCH_MNT/a
> > > +
> > > + # See if scrub complains...
> > > + if [ -n "$(_is_mounted $SCRATCH_DEV 2>&1)" ] && \
> > > + _supports_xfs_scrub $SCRATCH_MNT $SCRATCH_DEV; then
> > > + echo "SCRUB" >> $seqres.full
> > > + "$XFS_SCRUB_PROG" -n $SCRATCH_MNT >> $seqres.full
> > > + fi
> >
> > Is a scrub necessary for the test? Either way, I wonder if this is
> > something that is better paired with the repair in runtest().
>
> Probably can be omitted for now.
>
> > > +
> > > + _scratch_unmount 2>&1 | _filter_scratch
> > > +}
> > > +
> > > +runtest() {
> > > + cmd="$1"
> > > +
> > > + # Format filesystem
> > > + echo "TEST $cmd" | tee /dev/ttyprintk
> > > + echo "TEST $cmd" >> $seqres.full
> > > + _scratch_unmount >> /dev/null 2>&1
> > > + _scratch_mkfs_sized $((32 * 1048576)) >> $seqres.full
> > > +
> > > + # Record what was here before
> > > + echo "FS BEFORE" >> $seqres.full
> > > + _scratch_xfs_db -c 'sb 0' -c 'p' -c 'agf 0' -c 'p' -c 'agfl 0' -c 'p' > $tmp.before
> > > + cat $tmp.before >> $seqres.full
> > > +
> > > + sectsize=$(_scratch_xfs_get_metadata_field "sectsize" "sb 0")
> > > + flfirst=$(_scratch_xfs_get_metadata_field "flfirst" "agf 0")
> > > + fllast=$(_scratch_xfs_get_metadata_field "fllast" "agf 0")
> > > + flcount=$(_scratch_xfs_get_metadata_field "flcount" "agf 0")
> > > +
> > > + # Due to a padding bug in the original v5 struct xfs_agfl,
> > > + # XFS_AGFL_SIZE could be 36 on 32-bit or 40 on 64-bit. On a system
> > > + # with 512b sectors, this means that the AGFL length could be
> > > + # ((512 - 36) / 4) = 119 entries on 32-bit or ((512 - 40) / 4) = 118
> > > + # entries on 64-bit.
> > > + #
> > > + # We now have code to figure out if the AGFL list wraps incorrectly
> > > + # according to the kernel's agfl size and fix it by resetting the agfl
> > > + # to zero length. Mutate ag 0's agfl to be in various configurations
> > > + # and see if we can trigger the reset.
> > > + #
> > > + # Don't hardcode the numbers, calculate them.
> > > +
> > > + # Have to have at least three agfl items to test full wrap
> > > + test "$flcount" -ge 3 || _notrun "insufficient agfl flcount"
> > > +
> > > + # mkfs should be able to make us a nice neat flfirst < fllast setup
> > > + test "$flfirst" -lt "$fllast" || _notrun "fresh agfl already wrapped?"
> > > +
> > > + bad_agfl_size=$(( (sectsize - 40) / 4 ))
> > > + good_agfl_size=$(( (sectsize - 36) / 4 ))
> > > + agfl_size=
> > > + case "$1" in
> > > + "fix_end") # fllast points to the end w/ 40-byte padding
> > > + new_flfirst=$(( bad_agfl_size - flcount ))
> > > + agfl_size=$bad_agfl_size;;
> > > + "fix_start") # flfirst points to the end w/ 40-byte padding
> > > + new_flfirst=$(( bad_agfl_size - 1))
> > > + agfl_size=$bad_agfl_size;;
> > > + "fix_wrap") # list wraps around end w/ 40-byte padding
> > > + new_flfirst=$(( bad_agfl_size - (flcount / 2) ))
> > > + agfl_size=$bad_agfl_size;;
> > > + "start_zero") # flfirst points to the start
> > > + new_flfirst=0
> > > + agfl_size=$good_agfl_size;;
> > > + "good_end") # fllast points to the end w/ 36-byte padding
> > > + new_flfirst=$(( good_agfl_size - flcount ))
> > > + agfl_size=$good_agfl_size;;
> > > + "good_start") # flfirst points to the end w/ 36-byte padding
> > > + new_flfirst=$(( good_agfl_size - 1 ))
> > > + agfl_size=$good_agfl_size;;
> > > + "good_wrap") # list wraps around end w/ 36-byte padding
> > > + new_flfirst=$(( good_agfl_size - (flcount / 2) ))
> > > + agfl_size=$good_agfl_size;;
> > > + "bad_start") # flfirst points off the end
> > > + new_flfirst=$good_agfl_size
> > > + agfl_size=$good_agfl_size;;
> > > + "no_move") # whatever mkfs formats (flfirst points to start)
> > > + new_flfirst=$flfirst
> > > + agfl_size=$good_agfl_size;;
> > > + "simple_move") # move list arbitrarily
> > > + new_flfirst=$((fllast + 1))
> > > + agfl_size=$good_agfl_size;;
> > > + *)
> > > + _fail "Internal test error";;
> > > + esac
> > > + new_fllast=$(( (new_flfirst + flcount - 1) % agfl_size ))
> > > +
> > > + # Log what we're doing...
> > > + cat >> $seqres.full << ENDL
> > > +sector size: $sectsize
> > > +bad_agfl_size: $bad_agfl_size [0 - $((bad_agfl_size - 1))]
> > > +good_agfl_size: $good_agfl_size [0 - $((good_agfl_size - 1))]
> > > +agfl_size: $agfl_size
> > > +flfirst: $flfirst
> > > +fllast: $fllast
> > > +flcount: $flcount
> > > +new_flfirst: $new_flfirst
> > > +new_fllast: $new_fllast
> > > +ENDL
> > > +
> > > + # Remap the agfl blocks
> > > + echo "$((good_agfl_size - 1)) 0xffffffff" > $tmp.remap
> > > + seq "$flfirst" "$fllast" | while read f; do
> > > + list_pos=$((f - flfirst))
> > > + dest_pos=$(( (new_flfirst + list_pos) % agfl_size ))
> > > + bno=$(_scratch_xfs_get_metadata_field "bno[$f]" "agfl 0")
> > > + echo "$dest_pos $bno" >> $tmp.remap
> > > + done
> > > +
> > > + cat $tmp.remap | while read dest_pos bno junk; do
> > > + _scratch_xfs_set_metadata_field "bno[$dest_pos]" "$bno" "agfl 0" >> $seqres.full
> > > + done
> > > +
> >
> > Might be worth factoring the above into a function. Also, do we need all
> > of the $seqres.full redirection if we dump the $tmp.corrupt bits right
> > after?
>
> Probably not, but I like to preserve the log of what xfs_db did vs. what
> ended up on disk just to confirm that the
> _scratch_xfs_set_metadata_field are behaving like they're supposed to.
>
> > > + # Set new flfirst/fllast
> > > + _scratch_xfs_set_metadata_field "fllast" "$new_fllast" "agf 0" >> $seqres.full
> > > + _scratch_xfs_set_metadata_field "flfirst" "$new_flfirst" "agf 0" >> $seqres.full
> > > +
> > > + echo "FS AFTER" >> $seqres.full
> > > + _scratch_xfs_db -c 'sb 0' -c 'p' -c 'agf 0' -c 'p' -c 'agfl 0' -c 'p' > $tmp.corrupt 2> /dev/null
> > > + diff -u $tmp.before $tmp.corrupt >> $seqres.full
> > > +
> > > + # Mount and see what happens
> > > + mount_loop
> > > +
> > > + # Did we end up with a non-wrapped list?
> > > + flfirst=$(_scratch_xfs_get_metadata_field "flfirst" "agf 0" 2>/dev/null)
> > > + fllast=$(_scratch_xfs_get_metadata_field "fllast" "agf 0" 2>/dev/null)
> > > + if [ "${flfirst}" -ge "$((good_agfl_size - 1))" ]; then
> > > + echo "expected flfirst < good_agfl_size - 1"
> > > + echo "expected flfirst(${flfirst}) < good_agfl_size - 1($((good_agfl_size - 1)))" >> $seqres.full
> > > + fi
> > > + if [ "${fllast}" -ge "$((good_agfl_size - 1))" ]; then
> > > + echo "expected fllast < good_agfl_size - 1"
> > > + echo "expected fllast(${fllast}) < good_agfl_size - 1($((good_agfl_size - 1)))" >> $seqres.full
> > > + fi
> > > + if [ "${flfirst}" -ge "${fllast}" ]; then
> > > + echo "expected flfirst < fllast"
> > > + echo "expected flfirst(${flfirst}) < fllast(${fllast})" >> $seqres.full
> > > + fi
> >
> > Might be able to use tee here to avoid some of the echo duplication. It
> > looks like we already dump the raw agf/agfl structures to $seqres.full
> > below.
> >
> > Also note that there are a bunch of lines beyond 80 chars.
> >
> > > +
> > > + echo "FS MOUNTLOOP" >> $seqres.full
> > > + _scratch_xfs_db -c 'sb 0' -c 'p' -c 'agf 0' -c 'p' -c 'agfl 0' -c 'p' > $tmp.mountloop 2> /dev/null
> > > + diff -u $tmp.corrupt $tmp.mountloop >> $seqres.full
> > > +
> > > + # Let's see what repair thinks
> > > + echo "REPAIR" >> $seqres.full
> > > + _scratch_xfs_repair >> $seqres.full 2>&1
> >
> > I guess we don't need _require_scratch_nocheck if we repair before the
> > test returns.
>
> Yep.
>
> > > +
> > > + echo "FS REPAIR" >> $seqres.full
> > > + _scratch_xfs_db -c 'sb 0' -c 'p' -c 'agf 0' -c 'p' -c 'agfl 0' -c 'p' > $tmp.repair 2> /dev/null
> > > + diff -u $tmp.mountloop $tmp.repair >> $seqres.full
> > > +
> > > + # Try mount/unmount one more time.
> > > + mount_loop
> > > +
> > > + echo "FS REMOUNT" >> $seqres.full
> > > + _scratch_xfs_db -c 'sb 0' -c 'p' -c 'agf 0' -c 'p' -c 'agfl 0' -c 'p' > $tmp.remount 2> /dev/null
> > > + diff -u $tmp.repair $tmp.remount >> $seqres.full
> >
> > These last couple of hunks seem superfluous. What's the purpose, just to
> > work out the fs some more? I suppose that makes sense. The comment could
> > be made more clear.
>
> # Exercise the filesystem again to make sure there aren't any lasting
> # ill effects from either the agfl reset or the recommended subsequent
> # repair run.
>
> > > +}
> > > +
> > > +runtest fix_end
> > > +runtest fix_start
> > > +runtest fix_wrap
> > > +runtest start_zero
> > > +runtest good_end
> > > +runtest good_start
> > > +runtest good_wrap
> > > +runtest bad_start
> > > +runtest no_move
> > > +runtest simple_move
> > > +
> > > +_scratch_unmount >> $seqres.full 2>&1
> > > +
> >
> > The scratch mounting/unmounting seems unbalanced. runtest() unmounts the
> > fs at the start, but it doesn't appear we ever call it with scratch
> > already mounted. The mount loop cycles the mount, so it seems it should
> > already be unmounted by the time we get here as well.
>
> I think that's a desperate last gasp attempt to scrape the fs off the
> system when I was working on my version of the patch. It can go away.
>
> Thanks for the review! :)
>
> --D
>
> > Brian
> >
> > > +# Did we get the kernel warning too?
> > > +warn_str='WARNING: Reset corrupted AGFL'
> > > +_check_dmesg_for "${warn_str}" || echo "Missing kernel log message \"${warn_str}\"."
> > > +
> > > +# Now run the regular dmesg check, filtering out the agfl warning
> > > +filter_agfl_reset_printk() {
> > > + grep -v "${warn_str}"
> > > +}
> > > +_check_dmesg filter_agfl_reset_printk
> > > +
> > > +status=0
> > > +exit 0
> > > diff --git a/tests/xfs/709.out b/tests/xfs/709.out
> > > new file mode 100644
> > > index 0000000..980b4d1
> > > --- /dev/null
> > > +++ b/tests/xfs/709.out
> > > @@ -0,0 +1,13 @@
> > > +QA output created by 709
> > > +TEST fix_end
> > > +TEST fix_start
> > > +TEST fix_wrap
> > > +TEST start_zero
> > > +TEST good_end
> > > +TEST good_start
> > > +TEST good_wrap
> > > +TEST bad_start
> > > +expected flfirst < good_agfl_size - 1
> > > +expected flfirst < fllast
> > > +TEST no_move
> > > +TEST simple_move
> > > diff --git a/tests/xfs/group b/tests/xfs/group
> > > index e2397fe..472120e 100644
> > > --- a/tests/xfs/group
> > > +++ b/tests/xfs/group
> > > @@ -441,3 +441,4 @@
> > > 441 auto quick clone quota
> > > 442 auto stress clone quota
> > > 443 auto quick ioctl fsr
> > > +709 auto quick
> > > --
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