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btrfs: fix extent map logging bit not cleared for split maps after dropping range

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At btrfs_drop_extent_map_range() we are clearing the EXTENT_FLAG_LOGGING
bit on a 'flags' variable that was not initialized. This makes static
checkers complain about it, so initialize the 'flags' variable before
clearing the bit.

In practice this has no consequences, because EXTENT_FLAG_LOGGING should
not be set when btrfs_drop_extent_map_range() is called, as an fsync locks
the inode in exclusive mode, locks the inode's mmap semaphore in exclusive
mode too and it always flushes all delalloc.

Also add a comment about why we clear EXTENT_FLAG_LOGGING on a copy of the
flags of the split extent map.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/Y%2FyipSVozUDEZKow@kili/
Fixes: db21370bffbc ("btrfs: drop extent map range more efficiently")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2023-02-27 12:53:56 +00:00 committed by David Sterba
parent 95cd356ca2
commit e4cc1483f3
1 changed files with 6 additions and 1 deletions
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7
fs/btrfs/extent_map.c
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@ -763,7 +763,13 @@ void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
goto next;
}
flags = em->flags;
clear_bit(EXTENT_FLAG_PINNED, &em->flags);
/*
* In case we split the extent map, we want to preserve the
* EXTENT_FLAG_LOGGING flag on our extent map, but we don't want
* it on the new extent maps.
*/
clear_bit(EXTENT_FLAG_LOGGING, &flags);
modified = !list_empty(&em->list);
@ -774,7 +780,6 @@ void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
if (em->start >= start && em_end <= end)
goto remove_em;
flags = em->flags;
gen = em->generation;
compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);