Hi Andrew,
Please send this bug-fix to upstream. It fixes a file system
corruption problem in a near disk full condition.
Thanks,
Ryusuke Konishi
On Thu, 9 Jan 2014 02:22:15 +0900, Ryusuke Konishi wrote:
> From: Andreas Rohner <andreas.rohner@xxxxxxx>
>
> There is a bug in the function nilfs_segctor_collect, which results in
> active data being written to a segment, that is marked as clean. It is
> possible, that this segment is selected for a later segment
> construction, whereby the old data is overwritten.
>
> The problem shows itself with the following kernel log message:
>
> nilfs_sufile_do_cancel_free: segment 6533 must be clean
>
> Usually a few hours later the file system gets corrupted:
>
> NILFS: bad btree node (blocknr=8748107): level = 0, flags = 0x0,
> nchildren = 0
> NILFS error (device sdc1): nilfs_bmap_last_key: broken bmap
> (inode number=114660)
>
> The issue can be reproduced with a file system that is nearly full and
> with the cleaner running, while some IO intensive task is running.
> Although it is quite hard to reproduce.
>
> This is what happens:
>
> 1. The cleaner starts the segment construction
> 2. nilfs_segctor_collect is called
> 3. sc_stage is on NILFS_ST_SUFILE and segments are freed
> 4. sc_stage is on NILFS_ST_DAT current segment is full
> 5. nilfs_segctor_extend_segments is called, which
> allocates a new segment
> 6. The new segment is one of the segments freed in step 3
> 7. nilfs_sufile_cancel_freev is called and produces an error message
> 8. Loop around and the collection starts again
> 9. sc_stage is on NILFS_ST_SUFILE and segments are freed
> including the newly allocated segment, which will contain active data
> and can be allocated at a later time
> 10. A few hours later another segment construction allocates the segment
> and causes file system corruption
>
> This can be prevented by simply reordering the statements. If
> nilfs_sufile_cancel_freev is called before nilfs_segctor_extend_segments
> the freed segments are marked as dirty and cannot be allocated any more.
>
> Signed-off-by: Andreas Rohner <andreas.rohner@xxxxxxx>
> Reviewed-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
> Tested-by: Andreas Rohner <andreas.rohner@xxxxxxx>
> Cc: stable <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
> ---
> fs/nilfs2/segment.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
> index 9f6b486..a1a1916 100644
> --- a/fs/nilfs2/segment.c
> +++ b/fs/nilfs2/segment.c
> @@ -1440,17 +1440,19 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
>
> nilfs_clear_logs(&sci->sc_segbufs);
>
> - err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
> - if (unlikely(err))
> - return err;
> -
> if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
> err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
> sci->sc_freesegs,
> sci->sc_nfreesegs,
> NULL);
> WARN_ON(err); /* do not happen */
> + sci->sc_stage.flags &= ~NILFS_CF_SUFREED;
> }
> +
> + err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
> + if (unlikely(err))
> + return err;
> +
> nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
> sci->sc_stage = prev_stage;
> }
> --
> 1.7.9.3
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