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charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org sestd., 2021. g. 20. marts, plkst. 02:34 =E2=80=94 lietot=C4=81js Qu Wenruo () rakst=C4=ABja: > > > > On 2021/3/19 =E4=B8=8B=E5=8D=8811:34, D=C4=81vis Mos=C4=81ns wrote: > > ceturtd., 2021. g. 18. marts, plkst. 01:49 =E2=80=94 lietot=C4=81js Qu = Wenruo > > () rakst=C4=ABja: > >> > >> > >> > >> On 2021/3/18 =E4=B8=8A=E5=8D=885:03, D=C4=81vis Mos=C4=81ns wrote: > >>> tre=C5=A1d., 2021. g. 17. marts, plkst. 12:28 =E2=80=94 lietot=C4=81j= s Qu Wenruo > >>> () rakst=C4=ABja: > >>>> > >>>> > >>>> > >>>> On 2021/3/17 =E4=B8=8A=E5=8D=889:29, D=C4=81vis Mos=C4=81ns wrote: > >>>>> tre=C5=A1d., 2021. g. 17. marts, plkst. 03:18 =E2=80=94 lietot=C4= =81js D=C4=81vis Mos=C4=81ns > >>>>> () rakst=C4=ABja: > >>>>>> > >>>>>> 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: D=C4=81vis Mos=C4=81ns > >>>>>> --- > >>>>>> 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 =3D check_chunk_block_group_mappings(info); > >>>>>> error: > >>>>>> btrfs_free_path(path); > >>>>>> + > >>>>>> + if (ret =3D=3D -EIO && btrfs_test_opt(info, IGNOREBADROOTS= )) { > >>>>>> + btrfs_put_block_group_cache(info); > >>>>>> + btrfs_stop_all_workers(info); > >>>>>> + btrfs_free_block_groups(info); > >>>>>> + ret =3D btrfs_init_workqueues(info, NULL); > >>>>>> + if (ret) > >>>>>> + return ret; > >>>>>> + ret =3D 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 mounti= ng > >>>> the fs RO, or we can't continue. > >>>> > >>>> And we should also refuse to mount back to RW if we hit such case, s= o > >>>> that we don't need anything complex, just ignore the whole extent tr= ee > >>>> 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 easi= est > >>>>> 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 fail= ed > >>>>> on 21057127661568 wanted 0xd1506ed9 found 0x22ab750a level 0 > >>>>> [ 1398.218803] BTRFS warning (device sde): sde checksum verify fail= ed > >>>>> on 21057127661568 wanted 0xd1506ed9 found 0x7dd54bb9 level 0 > >>>>> [ 1398.218813] BTRFS: error (device sde) in __btrfs_free_extent:305= 4: > >>>>> errno=3D-5 IO failure > >>>>> [ 1398.218828] BTRFS: error (device sde) in > >>>>> btrfs_run_delayed_refs:2124: errno=3D-5 IO failure > >>>>> [ 1398.219002] BTRFS: error (device sde) in btrfs_replay_log:2254: > >>>>> errno=3D-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 reje= ct > >> 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, D=C4=81vis