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 commitdf2fd88f8a
("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>
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@ -784,6 +784,7 @@ xfs_reflink_end_cow_extent(
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}
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}
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del = got;
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xfs_trim_extent(&del, *offset_fsb, end_fsb - *offset_fsb);
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/* Grab the corresponding mapping in the data fork. */
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nmaps = 1;
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