Re: [PATCH 07/11] xfs_repair: force not-so-bad bmbt blocks back through the verifier
From: Dave Chinner <david@fromorbit.com>
Date: 2015-08-26 00:55:02
On Tue, Aug 25, 2015 at 05:33:05PM -0700, Darrick J. Wong wrote:
quoted hunk ↗ jump to hunk
If during prefetch we encounter a bmbt block that fails the CRC check due to corruption in the unused part of the block, force the buffer back through the non-prefetch verifiers later so that the CRC is updated. Otherwise, the bad checksum goes unfixed and the kernel will still flag the bmbt block as invalid. Signed-off-by: Darrick J. Wong <redacted> --- repair/prefetch.c | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/repair/prefetch.c b/repair/prefetch.c index 1de3ec0..77d29c8 100644 --- a/repair/prefetch.c +++ b/repair/prefetch.c@@ -276,6 +276,14 @@ pf_scan_lbtree( XFS_BUF_SET_PRIORITY(bp, isadir ? B_DIR_BMAP : B_BMAP); + /* + * Make this bmbt buffer go back through the verifiers later so that + * we correct checksum errors stemming from bitflips in the unused + * parts of the bmbt block. + */ + if (bp->b_error == -EFSBADCRC) + bp->b_flags |= LIBXFS_B_UNCHECKED;
This is because the next read of the buffer clears bp->b_error,
right?
So, while I think this is necessary, I also think the prefetch on
this btree should stop as we can't trust the contents of the buffer
to be correct. Hence I'd suggest that:
/*
* If the verfier flagged a problem with the buffer, we
* can't trust it's contents for the purposes of readahead.
* Stop prefetching the tree, and mark this buffer as
* unchecked so that the next read of the buffer by the
* repair code will retain the error status and hence be
* acted on appropriately.
*/
if (bp->b_error) {
bp->b_flags |= LIBXFS_B_UNCHECKED;
libxfs_putbuf(bp);
return 0;
}
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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