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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: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Filipe Manana 2014-08-04 19:37:21 +01:00 committed by Chris Mason
parent 79aec2b80d
commit f98de9b9c0
5 changed files with 7 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
fs/btrfs/ctree.c
View File

@ -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 @@ find_next_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 @@ find_next_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;
}

5
fs/btrfs/ioctl.c
View File

@ -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) {

3
fs/btrfs/tree-log.c
View File

@ -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;

1
fs/btrfs/uuid-tree.c
View File

@ -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)

2
fs/btrfs/volumes.c
View File

@ -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) {