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Commit dc7fdde3 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: reduce lock contention during extent insertion 



We're spending huge amounts of time on lock contention during
end_io processing because we unconditionally assume we are overwriting
an existing extent in the file for each IO.

This checks to see if we are outside i_size, and if so, it uses a
less expensive readonly search of the btree to look for existing
extents.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent fede766f

fs/btrfs/file.c

+7 −2
Original line number Diff line number Diff line
@@ -567,6 +567,7 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode, 
	int extent_type;

	int recow;

	int ret;

	int modify_tree = -1;



	if (drop_cache)

		btrfs_drop_extent_cache(inode, start, end - 1, 0);
@@ -575,10 +576,13 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode, 
	if (!path)

		return -ENOMEM;



	if (start >= BTRFS_I(inode)->disk_i_size)

		modify_tree = 0;



	while (1) {

		recow = 0;

		ret = btrfs_lookup_file_extent(trans, root, path, ino,

					       search_start, -1);

					       search_start, modify_tree);

		if (ret < 0)

			break;

		if (ret > 0 && path->slots[0] > 0 && search_start == start) {
@@ -634,7 +638,8 @@ next_slot: 
		}



		search_start = max(key.offset, start);

		if (recow) {

		if (recow || !modify_tree) {

			modify_tree = -1;

			btrfs_release_path(path);

			continue;

		}