Commit e4cc1483 authored Feb 27, 2023 by Filipe Manana Committed by David Sterba Mar 06, 2023

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



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: db21370b ("btrfs: drop extent map range more efficiently")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 95cd356c

fs/btrfs/extent_map.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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);