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Btrfs: fix releasepage to avoid unlocking extents we haven't locked
During releasepage, we try to drop any extent_state structs for the bye offsets of the page we're releaseing. But the code was incorrectly telling clear_extent_bit to delete the state struct unconditionallly. Normally this would be fine because we have the page locked, but other parts of btrfs will lock down an entire extent, the most common place being IO completion. releasepage was deleting the extent state without first locking the extent, which may result in removing a state struct that another process had locked down. The fix here is to leave the NODATASUM and EXTENT_LOCKED bits alone in releasepage. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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1 changed files with 7 additions and 2 deletions
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@ -2809,8 +2809,13 @@ int try_release_extent_state(struct extent_map_tree *map,
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else {
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if ((mask & GFP_NOFS) == GFP_NOFS)
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mask = GFP_NOFS;
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clear_extent_bit(tree, start, end, EXTENT_UPTODATE,
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1, 1, NULL, mask);
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/*
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* at this point we can safely clear everything except the
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* locked bit and the nodatasum bit
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*/
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clear_extent_bit(tree, start, end,
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~(EXTENT_LOCKED | EXTENT_NODATASUM),
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0, 0, NULL, mask);
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}
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return ret;
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}
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