btrfs: add specific helper for range bit test exists

The existing helper test_range_bit works in two ways, checks if the whole
range contains all the bits, or stop on the first occurrence.  By adding
a specific helper for the latter case, the inner loop can be simplified
and contains fewer conditionals, making it a bit faster.

There's no caller that uses the cached state pointer so this reduces the
argument count further.

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/defrag.c

@@ -1035,8 +1035,8 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
 		 *    very likely resulting in a larger extent after writeback is
 		 *    triggered (except in a case of free space fragmentation).
 		 */
-		if (test_range_bit(&inode->io_tree, cur, cur + range_len - 1,
-				   EXTENT_DELALLOC, 0, NULL))
+		if (test_range_bit_exists(&inode->io_tree, cur, cur + range_len - 1,
+					  EXTENT_DELALLOC))
 			goto next;
 
 		/*

fs/btrfs/extent-io-tree.c

@@ -1639,6 +1639,37 @@ search:
 	return total_bytes;
 }
 
+/*
+ * Check if the single @bit exists in the given range.
+ */
+bool test_range_bit_exists(struct extent_io_tree *tree, u64 start, u64 end, u32 bit)
+{
+	struct extent_state *state = NULL;
+	bool bitset = false;
+
+	ASSERT(is_power_of_2(bit));
+
+	spin_lock(&tree->lock);
+	state = tree_search(tree, start);
+	while (state && start <= end) {
+		if (state->start > end)
+			break;
+
+		if (state->state & bit) {
+			bitset = true;
+			break;
+		}
+
+		/* If state->end is (u64)-1, start will overflow to 0 */
+		start = state->end + 1;
+		if (start > end || start == 0)
+			break;
+		state = next_state(state);
+	}
+	spin_unlock(&tree->lock);
+	return bitset;
+}
+
 /*
  * Search a range in the state tree for a given mask.  If 'filled' == 1, this
  * returns 1 only if every extent in the tree has the bits set.  Otherwise, 1

fs/btrfs/extent-io-tree.h

@@ -133,6 +133,7 @@ u64 count_range_bits(struct extent_io_tree *tree,
 void free_extent_state(struct extent_state *state);
 int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		   u32 bits, int filled, struct extent_state *cached_state);
+bool test_range_bit_exists(struct extent_io_tree *tree, u64 start, u64 end, u32 bit);
 int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 			     u32 bits, struct extent_changeset *changeset);
 int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,

fs/btrfs/extent_io.c

@@ -2293,7 +2293,7 @@ static int try_release_extent_state(struct extent_io_tree *tree,
 	u64 end = start + PAGE_SIZE - 1;
 	int ret = 1;
 
-	if (test_range_bit(tree, start, end, EXTENT_LOCKED, 0, NULL)) {
+	if (test_range_bit_exists(tree, start, end, EXTENT_LOCKED)) {
 		ret = 0;
 	} else {
 		u32 clear_bits = ~(EXTENT_LOCKED | EXTENT_NODATASUM |
@@ -2352,9 +2352,9 @@ int try_release_extent_mapping(struct page *page, gfp_t mask)
 				free_extent_map(em);
 				break;
 			}
-			if (test_range_bit(tree, em->start,
-					   extent_map_end(em) - 1,
-					   EXTENT_LOCKED, 0, NULL))
+			if (test_range_bit_exists(tree, em->start,
+						  extent_map_end(em) - 1,
+						  EXTENT_LOCKED))
 				goto next;
 			/*
 			 * If it's not in the list of modified extents, used

fs/btrfs/inode.c

@@ -2239,8 +2239,7 @@ static bool should_nocow(struct btrfs_inode *inode, u64 start, u64 end)
 {
 	if (inode->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC)) {
 		if (inode->defrag_bytes &&
-		    test_range_bit(&inode->io_tree, start, end, EXTENT_DEFRAG,
-				   0, NULL))
+		    test_range_bit_exists(&inode->io_tree, start, end, EXTENT_DEFRAG))
 			return false;
 		return true;
 	}
@@ -7111,8 +7110,7 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
 
 		range_end = round_up(offset + nocow_args.num_bytes,
 				     root->fs_info->sectorsize) - 1;
-		ret = test_range_bit(io_tree, offset, range_end,
-				     EXTENT_DELALLOC, 0, NULL);
+		ret = test_range_bit_exists(io_tree, offset, range_end, EXTENT_DELALLOC);
 		if (ret) {
 			ret = -EAGAIN;
 			goto out;