Messages in this thread | | | Subject | Re: [RFC] btrfs: Allow read-only mount with corrupted extent tree | From | Qu Wenruo <> | Date | Thu, 18 Mar 2021 07:49:29 +0800 |
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On 2021/3/18 上午5:03, Dāvis Mosāns wrote: > trešd., 2021. g. 17. marts, plkst. 12:28 — lietotājs Qu Wenruo > (<quwenruo.btrfs@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 >>> (<davispuh@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 <davispuh@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.
Thanks, Qu
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