[PATCH 12/22] btrfs: avoid researching tree when converting bits in an extent range

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

When converting bits for an extent range (btrfs_convert_extent_bit()), if
the current extent state record starts after the target range, we always
do a jump to the 'search_again' label, which will cause us to do a full
tree search for the next state if the current state ends before the target
range. Unless we need to reschedule, we can just grab the next state and
process it, avoiding a full tree search, even if that next state is not
contiguous, as we'll allocate and insert a new prealloc state if needed.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/extent-io-tree.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/fs/btrfs/extent-io-tree.c b/fs/btrfs/extent-io-tree.c
index a898a15a7854..65665c0843e6 100644
--- a/fs/btrfs/extent-io-tree.c
+++ b/fs/btrfs/extent-io-tree.c
@@ -1458,6 +1458,22 @@ int btrfs_convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		if (inserted_state == prealloc)
 			prealloc = NULL;
 		start = inserted_state->end + 1;
+
+		/* Beyond target range, stop. */
+		if (start > end)
+			goto out;
+
+		if (need_resched())
+			goto search_again;
+
+		state = next_search_state(inserted_state, end);
+		/*
+		 * If there's a next state, whether contiguous or not, we don't
+		 * need to unlock and research. If it's not contiguous we will
+		 * end up here and try to allocate a prealloc state and insert.
+		 */
+		if (state)
+			goto hit_next;
 		goto search_again;
 	}
 	/*
-- 
2.47.2