Re: [PATCH v2] btrfs-progs: test-misc: search the backup slot to use at runtime

[Josef Bacik <josef@toxicpanda.com>]

On Fri, Oct 15, 2021 at 06:36:36AM +0800, Qu Wenruo wrote:
> 
> 
> On 2021/10/14 23:36, Josef Bacik wrote:
> > On Wed, Oct 13, 2021 at 09:12:33AM +0800, Qu Wenruo wrote:
> > > Test case misc/038 uses hardcoded backup slot number, this means if we
> > > change how many transactions we commit during mkfs, it will immediately
> > > break the tests.
> > > 
> > > Such hardcoded tests will be a big pain for later btrfs-progs updates.
> > > 
> > > Update it with runtime backup slot search.
> > > 
> > > Such search is done by using current filesystem generation as a search
> > > target and grab the slot number.
> > > 
> > > By this, no matter how many transactions we commit during mkfs, the test
> > > case should be able to handle it.
> > > 
> > > Signed-off-by: Qu Wenruo <wqu@suse.com>
> > > ---
> > > Changelog:
> > > v2:
> > > - Use run_check() instead of manually redirect output to "$RESULT"
> > > - Quote "$main_root_ptr"
> > > ---
> > >   .../038-backup-root-corruption/test.sh        | 47 ++++++++++++-------
> > >   1 file changed, 29 insertions(+), 18 deletions(-)
> > > 
> > > diff --git a/tests/misc-tests/038-backup-root-corruption/test.sh b/tests/misc-tests/038-backup-root-corruption/test.sh
> > > index b6c3671f2c3a..bf41f1e0952b 100755
> > > --- a/tests/misc-tests/038-backup-root-corruption/test.sh
> > > +++ b/tests/misc-tests/038-backup-root-corruption/test.sh
> > > @@ -17,25 +17,35 @@ run_check $SUDO_HELPER touch "$TEST_MNT/file"
> > >   run_check_umount_test_dev
> > > 
> > >   dump_super() {
> > > -	run_check_stdout $SUDO_HELPER "$TOP/btrfs" inspect-internal dump-super -f "$TEST_DEV"
> > > +	# In this test, we will dump super block multiple times, while the
> > > +	# existing run_check*() helpers will always dump all the output into
> > > +	# the log, flooding the log and hide real important info.
> > > +	# Thus here we call "btrfs" directly.
> > > +	$SUDO_HELPER "$TOP/btrfs" inspect-internal dump-super -f "$TEST_DEV"
> > >   }
> > > 
> > > -# Ensure currently active backup slot is the expected one (slot 3)
> > > -backup2_root_ptr=$(dump_super | grep -A1 "backup 2" | grep backup_tree_root | awk '{print $2}')
> > > -
> > >   main_root_ptr=$(dump_super | awk '/^root\t/{print $2}')
> > > +# Grab current fs generation, and it will be used to determine which backup
> > > +# slot to use
> > > +cur_gen=$(dump_super | grep ^generation | awk '{print $2}')
> > > +backup_gen=$(($cur_gen - 1))
> > > +
> > > +# Grab the slot which matches @backup_gen
> > > +found=$(dump_super | grep backup_tree_root | grep -n "gen: $backup_gen")
> > > 
> > > -if [ "$backup2_root_ptr" -ne "$main_root_ptr" ]; then
> > > -	_log "Backup slot 2 not in use, trying slot 3"
> > > -	# Or use the next slot in case of free-space-tree
> > > -	backup3_root_ptr=$(dump_super | grep -A1 "backup 3" | grep backup_tree_root | awk '{print $2}')
> > > -	if [ "$backup3_root_ptr" -ne "$main_root_ptr" ]; then
> > > -		_fail "Neither backup slot 2 nor slot 3 are in use"
> > > -	fi
> > > -	_log "Backup slot 3 in use"
> > > +if [ -z "$found" ]; then
> > > +	_fail "Unable to find a backup slot with generation $backup_gen"
> > >   fi
> > > 
> > > -run_check "$INTERNAL_BIN/btrfs-corrupt-block" -m $main_root_ptr -f generation "$TEST_DEV"
> > > +slot_num=$(echo $found | cut -f1 -d:)
> > > +# To follow the dump-super output, where backup slot starts at 0.
> > > +slot_num=$(($slot_num - 1))
> > 
> > What happens if we're on $slot_num == 0?  Seems like this would mess up, right?
> > Thanks,
> 
> Note that, the $found is from "grep -n" which starts its line number at 1.
> 
> Thus $slot_num will always be >= 1, and nothing will be wrong.
> 

I missed the -n part, sorry about that, you can add

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef