From d352ac68148b69937d39ca5d48bcc4478e118dbf Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Mon, 29 Sep 2008 15:18:18 -0400 Subject: 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 --- fs/btrfs/locking.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'fs/btrfs/locking.c') 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; -- cgit v1.2.3