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xfs: only remap the written blocks in xfs_reflink_end_cow_extent

xfs_reflink_end_cow_extent looks up the COW extent and the data fork
extent at offset_fsb, and then proceeds to remap the common subset
between the two.

It does however not limit the remapped extent to the passed in
[*offset_fsbm end_fsb] range and thus potentially remaps more blocks than
the one handled by the current I/O completion.  This means that with
sufficiently large data and COW extents we could be remapping COW fork
mappings that have not been written to, leading to a stale data exposure
on a powerfail event.

We use to have a xfs_trim_range to make the remap fit the I/O completion
range, but that got (apparently accidentally) removed in commit
df2fd88f8a ("xfs: rewrite xfs_reflink_end_cow to use intents").

Note that I've only found this by code inspection, and a test case would
probably require very specific delay and error injection.

Fixes: df2fd88f8a ("xfs: rewrite xfs_reflink_end_cow to use intents")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
This commit is contained in:
Christoph Hellwig 2023-10-16 17:28:52 +02:00 committed by Chandan Babu R
parent 0008050361
commit 55f669f341

View File

@ -784,6 +784,7 @@ xfs_reflink_end_cow_extent(
}
}
del = got;
xfs_trim_extent(&del, *offset_fsb, end_fsb - *offset_fsb);
/* Grab the corresponding mapping in the data fork. */
nmaps = 1;