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Commit f98de9b9 authored by Filipe Manana's avatar Filipe Manana Committed by Chris Mason
Browse files

Btrfs: make btrfs_search_forward return with nodes unlocked 



None of the uses of btrfs_search_forward() need to have the path
nodes (level >= 1) read locked, only the leaf needs to be locked
while the caller processes it. Therefore make it return a path
with all nodes unlocked, except for the leaf.

This change is motivated by the observation that during a file
fsync we repeatdly call btrfs_search_forward() and process the
returned leaf while upper nodes of the returned path (level >= 1)
are read locked, which unnecessarily blocks other tasks that want
to write to the same fs/subvol btree.
Therefore instead of modifying the fsync code to unlock all nodes
with level >= 1 immediately after calling btrfs_search_forward(),
change btrfs_search_forward() to do it, so that it benefits all
callers.

Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 79aec2b8

fs/btrfs/ctree.c

+7 −4
Original line number Diff line number Diff line
@@ -5144,8 +5144,9 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key, 
	u32 nritems;

	int level;

	int ret = 1;

	int keep_locks = path->keep_locks;



	WARN_ON(!path->keep_locks);

	path->keep_locks = 1;

again:

	cur = btrfs_read_lock_root_node(root);

	level = btrfs_header_level(cur);
@@ -5209,7 +5210,6 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key, 
		path->slots[level] = slot;

		if (level == path->lowest_level) {

			ret = 0;

			unlock_up(path, level, 1, 0, NULL);

			goto out;

		}

		btrfs_set_path_blocking(path);
@@ -5224,9 +5224,12 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key, 
		btrfs_clear_path_blocking(path, NULL, 0);

	}

out:

	if (ret == 0)

		memcpy(min_key, &found_key, sizeof(found_key));

	path->keep_locks = keep_locks;

	if (ret == 0) {

		btrfs_unlock_up_safe(path, path->lowest_level + 1);

		btrfs_set_path_blocking(path);

		memcpy(min_key, &found_key, sizeof(found_key));

	}

	return ret;

}

fs/btrfs/ioctl.c

+0 −5
Original line number Diff line number Diff line
@@ -936,12 +936,9 @@ static int find_new_extents(struct btrfs_root *root, 
	min_key.offset = *off;



	while (1) {

		path->keep_locks = 1;

		ret = btrfs_search_forward(root, &min_key, path, newer_than);

		if (ret != 0)

			goto none;

		path->keep_locks = 0;

		btrfs_unlock_up_safe(path, 1);

process_slot:

		if (min_key.objectid != ino)

			goto none;
@@ -2088,8 +2085,6 @@ static noinline int search_ioctl(struct inode *inode, 
	key.type = sk->min_type;

	key.offset = sk->min_offset;



	path->keep_locks = 1;



	while (1) {

		ret = btrfs_search_forward(root, &key, path, sk->min_transid);

		if (ret != 0) {

fs/btrfs/tree-log.c

+0 −3
Original line number Diff line number Diff line
@@ -2983,8 +2983,6 @@ static noinline int log_dir_items(struct btrfs_trans_handle *trans, 
	min_key.type = key_type;

	min_key.offset = min_offset;



	path->keep_locks = 1;



	ret = btrfs_search_forward(root, &min_key, path, trans->transid);



	/*
@@ -3964,7 +3962,6 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans, 
		err = ret;

		goto out_unlock;

	}

	path->keep_locks = 1;



	while (1) {

		ins_nr = 0;

fs/btrfs/uuid-tree.c

+0 −1
Original line number Diff line number Diff line
@@ -279,7 +279,6 @@ int btrfs_uuid_tree_iterate(struct btrfs_fs_info *fs_info, 
	key.offset = 0;



again_search_slot:

	path->keep_locks = 1;

	ret = btrfs_search_forward(root, &key, path, 0);

	if (ret) {

		if (ret > 0)

fs/btrfs/volumes.c

+0 −2
Original line number Diff line number Diff line
@@ -3625,8 +3625,6 @@ static int btrfs_uuid_scan_kthread(void *data) 
	max_key.type = BTRFS_ROOT_ITEM_KEY;

	max_key.offset = (u64)-1;



	path->keep_locks = 1;



	while (1) {

		ret = btrfs_search_forward(root, &key, path, 0);

		if (ret) {