sestd., 2021. g. 20. marts, plkst. 02:34 — lietotājs Qu Wenruo
(<quwenruo.bt...@gmx.com>) rakstīja:
>
>
>
> On 2021/3/19 下午11:34, Dāvis Mosāns wrote:
> > ceturtd., 2021. g. 18. marts, plkst. 01:49 — lietotājs Qu Wenruo
> > (<quwenruo.bt...@gmx.com>) rakstīja:
> >>
> >>
> >>
> >> On 2021/3/18 上午5:03, Dāvis Mosāns wrote:
> >>> trešd., 2021. g. 17. marts, plkst. 12:28 — lietotājs Qu Wenruo
> >>> (<quwenruo.bt...@gmx.com>) rakstīja:
> >>>>
> >>>>
> >>>>
> >>>> On 2021/3/17 上午9:29, Dāvis Mosāns wrote:
> >>>>> trešd., 2021. g. 17. marts, plkst. 03:18 — lietotājs Dāvis Mosāns
> >>>>> (<davis...@gmail.com>) rakstīja:
> >>>>>>
> >>>>>> Currently if there's any corruption at all in extent tree
> >>>>>> (eg. even single bit) then mounting will fail with:
> >>>>>> "failed to read block groups: -5" (-EIO)
> >>>>>> It happens because we immediately abort on first error when
> >>>>>> searching in extent tree for block groups.
> >>>>>>
> >>>>>> Now with this patch if `ignorebadroots` option is specified
> >>>>>> then we handle such case and continue by removing already
> >>>>>> created block groups and creating dummy block groups.
> >>>>>>
> >>>>>> Signed-off-by: Dāvis Mosāns <davis...@gmail.com>
> >>>>>> ---
> >>>>>> fs/btrfs/block-group.c | 14 ++++++++++++++
> >>>>>> fs/btrfs/disk-io.c | 4 ++--
> >>>>>> fs/btrfs/disk-io.h | 2 ++
> >>>>>> 3 files changed, 18 insertions(+), 2 deletions(-)
> >>>>>>
> >>>>>> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> >>>>>> index 48ebc106a606..827a977614b3 100644
> >>>>>> --- a/fs/btrfs/block-group.c
> >>>>>> +++ b/fs/btrfs/block-group.c
> >>>>>> @@ -2048,6 +2048,20 @@ int btrfs_read_block_groups(struct
> >>>>>> btrfs_fs_info *info)
> >>>>>> ret = check_chunk_block_group_mappings(info);
> >>>>>> error:
> >>>>>> btrfs_free_path(path);
> >>>>>> +
> >>>>>> + if (ret == -EIO && btrfs_test_opt(info, IGNOREBADROOTS)) {
> >>>>>> + btrfs_put_block_group_cache(info);
> >>>>>> + btrfs_stop_all_workers(info);
> >>>>>> + btrfs_free_block_groups(info);
> >>>>>> + ret = btrfs_init_workqueues(info, NULL);
> >>>>>> + if (ret)
> >>>>>> + return ret;
> >>>>>> + ret = btrfs_init_space_info(info);
> >>>>>> + if (ret)
> >>>>>> + return ret;
> >>>>>> + return fill_dummy_bgs(info);
> >>>>
> >>>> When we hit bad things in extent tree, we should ensure we're mounting
> >>>> the fs RO, or we can't continue.
> >>>>
> >>>> And we should also refuse to mount back to RW if we hit such case, so
> >>>> that we don't need anything complex, just ignore the whole extent tree
> >>>> and create the dummy block groups.
> >>>>
> >>>
> >>> That's what we're doing here, `ignorebadroots` implies RO mount and
> >>> without specifying it doesn't mount at all.
> >>>
> >>>>>
> >>>>> This isn't that nice, but I don't really know how to properly clean up
> >>>>> everything related to already created block groups so this was easiest
> >>>>> way. It seems to work fine.
> >>>>> But looks like need to do something about replay log aswell because if
> >>>>> it's not disabled then it fails with:
> >>>>>
> >>>>> [ 1397.246869] BTRFS info (device sde): start tree-log replay
> >>>>> [ 1398.218685] BTRFS warning (device sde): sde checksum verify failed
> >>>>> on 21057127661568 wanted 0xd1506ed9 found 0x22ab750a level 0
> >>>>> [ 1398.218803] BTRFS warning (device sde): sde checksum verify failed
> >>>>> on 21057127661568 wanted 0xd1506ed9 found 0x7dd54bb9 level 0
> >>>>> [ 1398.218813] BTRFS: error (device sde) in __btrfs_free_extent:3054:
> >>>>> errno=-5 IO failure
> >>>>> [ 1398.218828] BTRFS: error (device sde) in
> >>>>> btrfs_run_delayed_refs:2124: errno=-5 IO failure
> >>>>> [ 1398.219002] BTRFS: error (device sde) in btrfs_replay_log:2254:
> >>>>> errno=-5 IO failure (Failed to recover log tree)
> >>>>> [ 1398.229048] BTRFS error (device sde): open_ctree failed
> >>>>
> >>>> This is because we shouldn't allow to do anything write to the fs if we
> >>>> have anything wrong in extent tree.
> >>>>
> >>>
> >>> This is happening when mounting read-only. My assumption is that it
> >>> only tries to replay in memory without writing anything to disk.
> >>>
> >>
> >> We lacks the check on log tree.
> >>
> >> Normally for such forced RO mount, log replay is not allowed.
> >>
> >> We should output a warning to prompt user to use nologreplay, and reject
> >> the mount.
> >>
> >
> > I'm not familiar with log replay but couldn't there be something
> > useful (ignoring ref counts) that would still be worth replaying in
> > memory?
> >
> Log replay means metadata write.
>
> Any write needs a valid extent tree to find out free space for new
> metadata/data.
>
> So no, we can't do anything but completely ignoring the log.
>
I see, updated patch. But even then it seems it could be possible to
add new ramdisk and make allocations there (eg. create new extent tree
there) thus allowing replay. I guess that's way too much work.
Anyway thanks for feedback!
Best regards,
Dāvis
