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Commit cb25c2ea authored by Josef Bacik's avatar Josef Bacik
Browse files

Btrfs: map the node block when looking for readahead targets 



If we have particularly full nodes, we could call btrfs_node_blockptr up to 32
times, which is 32 pairs of kmap/kunmap, which _sucks_.  So go ahead and map the
extent buffer while we look for readahead targets.  Thanks,

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
parent af60bed2

fs/btrfs/ctree.c

+21 −2
Original line number Diff line number Diff line
@@ -1229,6 +1229,7 @@ static void reada_for_search(struct btrfs_root *root, 
	u64 search;

	u64 target;

	u64 nread = 0;

	u64 gen;

	int direction = path->reada;

	struct extent_buffer *eb;

	u32 nr;
@@ -1256,6 +1257,15 @@ static void reada_for_search(struct btrfs_root *root, 
	nritems = btrfs_header_nritems(node);

	nr = slot;

	while (1) {

		if (!node->map_token) {

			unsigned long offset = btrfs_node_key_ptr_offset(nr);

			map_private_extent_buffer(node, offset,

						  sizeof(struct btrfs_key_ptr),

						  &node->map_token,

						  &node->kaddr,

						  &node->map_start,

						  &node->map_len, KM_USER1);

		}

		if (direction < 0) {

			if (nr == 0)

				break;
@@ -1273,14 +1283,23 @@ static void reada_for_search(struct btrfs_root *root, 
		search = btrfs_node_blockptr(node, nr);

		if ((search <= target && target - search <= 65536) ||

		    (search > target && search - target <= 65536)) {

			readahead_tree_block(root, search, blocksize,

				     btrfs_node_ptr_generation(node, nr));

			gen = btrfs_node_ptr_generation(node, nr);

			if (node->map_token) {

				unmap_extent_buffer(node, node->map_token,

						    KM_USER1);

				node->map_token = NULL;

			}

			readahead_tree_block(root, search, blocksize, gen);

			nread += blocksize;

		}

		nscan++;

		if ((nread > 65536 || nscan > 32))

			break;

	}

	if (node->map_token) {

		unmap_extent_buffer(node, node->map_token, KM_USER1);

		node->map_token = NULL;

	}

}



/*