Re: [PATCH v3 1/2] fstests: Add more sanity to seek_sanity_test

Amir Goldstein
2019-04-03T16:22:58Z

On Wed, Apr 3, 2019 at 7:06 PM Darrick J. Wong <darrick.wong@oracle.com> wrote:
>
> On Wed, Apr 03, 2019 at 08:59:25AM +0300, Amir Goldstein wrote:
> > seek_sanity_test checks for one of several SEEK_DATA/HOLE
> > behaviors and allows for the default behavior of filesystems,
> > where SEEK_HOLE always returns EOF.
> >
> > This means that if filesystem has a regression in finding
> > holes, the sanity test won't catch it. And indeed this regression
> > happened in overlayfs on kernel v4.19 and went unnoticed.
> >
> > To improve test coverage, add a flag -f to seek_sanity_test to
> > indicate that the default behavior is not acceptable.
> > Whitelist all filesystem types that are expected to detect holes
> > and use wrapper when invoking seek_sanity_test to add the -f flag
> > to those filesystems.
> >
> > Overlayfs inherits expected behavior from base fs type.
> >
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > ---
> >
> > Eryu,
> >
> > Sorry for the delay.
> > Changes per your v2 review.
> >
> > Amir.
> >
> > Changes from v2:
> > - Rename helper to _fstyp_has_non_default_seek_data_hole
> > - Clarify documentation and error message
> > - Skip new test (seek to punched hole) on default_behavior
> >
> >
> > common/rc | 47 ++++++++++++++++++++++++++++++++++++++++++
> > src/seek_sanity_test.c | 14 +++++++++++--
> > tests/generic/285 | 2 +-
> > tests/generic/436 | 2 +-
> > tests/generic/445 | 2 +-
> > tests/generic/448 | 2 +-
> > tests/generic/490 | 2 +-
> > 7 files changed, 64 insertions(+), 7 deletions(-)
> >
> > diff --git a/common/rc b/common/rc
> > index 1c42515f..7b292321 100644
> > --- a/common/rc
> > +++ b/common/rc
> > @@ -2298,6 +2298,53 @@ _ext4_disable_extent_zeroout()
> > echo 0 >/sys/fs/ext4/$sdev/extent_max_zeroout_kb
> > }
> >
> > +# The default behavior of SEEK_HOLE is to always return EOF.
>
> I assume this statement applies even when there /is/ a hole in the file?
>
> As in, "Some filesystems return EOF even when there are holes", right?

Right.

>
> I wonder if there's a good way to fix SEEK_HOLE for those filesystems.
>
> > +# Filesystems that implement non-default behavior return the offset
>
> ...except for the magic filesystems below that actually return holes?

Yes.

>
> I suppose that works, since even the default behavior tells no
> falsehoods w.r.t. where might there data in a file.
>
> > +# of holes with SEEK_HOLE. There is no way to query the filesystem
> > +# of which behavior it is implementing.
> > +# We use this whitelist FSTYP, to set expectation and avoid silent
> > +# regression of filesystem seek hole behavior.
> > +#
> > +# Return 0 for true
> > +_fstyp_has_non_default_seek_data_hole()
> > +{
> > + if [ -z $1 ]; then
> > + local fstyp=$FSTYP
> > + else
> > + local fstyp=$1
> > + fi
> > +
> > + case "$fstyp" in
> > + btrfs|ext4|xfs|ceph|cifs|f2fs|gfs2|nfs*|ocfs2|tmpfs)
>
> Not a fan of whitelists, but I don't see a better way to do this.
>
> Acked-by: Darrick J. Wong <darrick.wong@oracle.com>
>
> --D
>
> > + return 0
> > + ;;
> > + overlay)
> > + if [ ! -z $OVL_BASE_FSTYP -a $OVL_BASE_FSTYP != "overlay" ]; then
> > + _fstyp_has_non_default_seek_data_hole $OVL_BASE_FSTYP
> > + return $?
> > + else
> > + # Assume that base fs has default behavior
> > + return 1
> > + fi
> > + ;;
> > + *)
> > + # by default fstyp has default SEEK_HOLE behavior;
> > + # if your fs has non-default behavior, add it to whitelist above!
> > + return 1
> > + ;;
> > + esac
> > +}
> > +
> > +# Run seek sanity test with predefined expectation for SEEK_DATA/HOLE behavior
> > +_run_seek_sanity_test()
> > +{
> > + local testseekargs
> > + if _fstyp_has_non_default_seek_data_hole; then
> > + testseekargs+="-f"
> > + fi
> > + $here/src/seek_sanity_test $testseekargs $*
> > +}
> > +
> > # Check if the file system supports seek_data/hole
> > _require_seek_data_hole()
> > {
> > diff --git a/src/seek_sanity_test.c b/src/seek_sanity_test.c
> > index e9938d1b..a6bda0b1 100644
> > --- a/src/seek_sanity_test.c
> > +++ b/src/seek_sanity_test.c
> > @@ -23,6 +23,7 @@
> > #endif
> >
> > static blksize_t alloc_size;
> > +int allow_default_behavior = 1;
> > int default_behavior = 0;
> > int unwritten_extents = 0;
> > char *base_file_path;
> > @@ -1119,6 +1120,12 @@ static int test_basic_support(void)
> > fprintf(stderr, "File system supports the default behavior.\n");
> > }
> >
> > + if (default_behavior && !allow_default_behavior) {
> > + fprintf(stderr, "Default behavior is not allowed. Aborting.\n");
> > + ret = -1;
> > + goto out;
> > + }
> > +
> > ftruncate(fd, 0);
> > if (fallocate(fd, 0, 0, alloc_size) == -1) {
> > if (errno == EOPNOTSUPP)
> > @@ -1148,7 +1155,7 @@ out:
> >
> > void usage(char *cmd)
> > {
> > - fprintf(stdout, "Usage: %s [-t] [-s <starttest>] [-e <endtest>] base_file_path\n", cmd);
> > + fprintf(stdout, "Usage: %s [-tf] [-s <starttest>] [-e <endtest>] base_file_path\n", cmd);
> > exit(1);
> > }
> >
> > @@ -1169,11 +1176,14 @@ int main(int argc, char **argv)
> > teststart = 1;
> > testend = 12;
> >
> > - while ((opt = getopt(argc, argv, "ts:e:")) != -1) {
> > + while ((opt = getopt(argc, argv, "tfs:e:")) != -1) {
> > switch (opt) {
> > case 't':
> > check_support++;
> > break;
> > + case 'f':
> > + allow_default_behavior = 0;
> > + break;
> > case 's':
> > teststart = strtol(optarg, NULL, 10);
> > if (teststart <= 0 || teststart > numtests) {
> > diff --git a/tests/generic/285 b/tests/generic/285
> > index b53b3acc..20e89e5b 100755
> > --- a/tests/generic/285
> > +++ b/tests/generic/285
> > @@ -37,7 +37,7 @@ _cleanup()
> > eval "rm -f $BASE_TEST_FILE.*"
> > }
> >
> > -$here/src/seek_sanity_test $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > +_run_seek_sanity_test $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > _fail "seek sanity check failed!"
> >
> > # success, all done
> > diff --git a/tests/generic/436 b/tests/generic/436
> > index a3ef70e5..ada60b2e 100755
> > --- a/tests/generic/436
> > +++ b/tests/generic/436
> > @@ -36,7 +36,7 @@ _cleanup()
> > rm -f $tmp.* $BASE_TEST_FILE.*
> > }
> >
> > -$here/src/seek_sanity_test -s 13 -e 16 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > +_run_seek_sanity_test -s 13 -e 16 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > _fail "seek sanity check failed!"
> >
> > # success, all done
> > diff --git a/tests/generic/445 b/tests/generic/445
> > index 694913ae..248f321b 100755
> > --- a/tests/generic/445
> > +++ b/tests/generic/445
> > @@ -36,7 +36,7 @@ _cleanup()
> > rm -f $tmp.* $BASE_TEST_FILE.*
> > }
> >
> > -$here/src/seek_sanity_test -s 17 -e 17 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > +_run_seek_sanity_test -s 17 -e 17 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > _fail "seek sanity check failed!"
> >
> > # success, all done
> > diff --git a/tests/generic/448 b/tests/generic/448
> > index d3ec5528..dada499b 100755
> > --- a/tests/generic/448
> > +++ b/tests/generic/448
> > @@ -34,7 +34,7 @@ BASE_TEST_FILE=$TEST_DIR/seek_sanity_testfile_$seq
> >
> > _require_test_program "seek_sanity_test"
> >
> > -$here/src/seek_sanity_test -s 18 -e 18 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > +_run_seek_sanity_test -s 18 -e 18 $BASE_TEST_FILE > $seqres.full 2>&1 ||
> > _fail "seek sanity check failed!"
> >
> > _check_dmesg
> > diff --git a/tests/generic/490 b/tests/generic/490
> > index 330c2b60..07b08939 100755
> > --- a/tests/generic/490
> > +++ b/tests/generic/490
> > @@ -39,7 +39,7 @@ _cleanup()
> > rm -f $base_test_file*
> > }
> >
> > -$here/src/seek_sanity_test -s 19 -e 20 $base_test_file > $seqres.full 2>&1 ||
> > +_run_seek_sanity_test -s 19 -e 20 $base_test_file > $seqres.full 2>&1 ||
> > _fail "seek sanity check failed!"
> >
> > # success, all done
> > --
> > 2.17.1
> >