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authorChris Mason <chris.mason@oracle.com>2008-09-29 15:18:18 -0400
committerChris Mason <chris.mason@oracle.com>2008-09-29 15:18:18 -0400
commitd352ac68148b69937d39ca5d48bcc4478e118dbf (patch)
tree7951dd7311999d9e77766acdc7f8e93de97874d8 /fs/btrfs/locking.c
parent9a5e1ea1e1e539e244a54afffc330fc368376ab9 (diff)
Btrfs: add and improve comments
This improves the comments at the top of many functions. It didn't dive into the guts of functions because I was trying to avoid merging problems with the new allocator and back reference work. extent-tree.c and volumes.c were both skipped, and there is definitely more work todo in cleaning and commenting the code. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/locking.c')
-rw-r--r--fs/btrfs/locking.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 0cc314c10d66..e30aa6e2958f 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -25,6 +25,15 @@
#include "extent_io.h"
#include "locking.h"
+/*
+ * locks the per buffer mutex in an extent buffer. This uses adaptive locks
+ * and the spin is not tuned very extensively. The spinning does make a big
+ * difference in almost every workload, but spinning for the right amount of
+ * time needs some help.
+ *
+ * In general, we want to spin as long as the lock holder is doing btree searches,
+ * and we should give up if they are in more expensive code.
+ */
int btrfs_tree_lock(struct extent_buffer *eb)
{
int i;
@@ -57,6 +66,10 @@ int btrfs_tree_locked(struct extent_buffer *eb)
return mutex_is_locked(&eb->mutex);
}
+/*
+ * btrfs_search_slot uses this to decide if it should drop its locks
+ * before doing something expensive like allocating free blocks for cow.
+ */
int btrfs_path_lock_waiting(struct btrfs_path *path, int level)
{
int i;