Btrfs: Use a mutex in the extent buffer for tree block locking

This replaces the use of the page cache lock bit for locking, which wasn't
suitable for block size < page size and couldn't be used recursively.

The mutexes alone don't fix either problem, but they are the first step.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 058a506a0dd8..01a9ac2be3f7 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -29,32 +29,31 @@ int btrfs_tree_lock(struct extent_buffer *eb)
 {
         int i;
 
-        if (!TestSetPageLocked(eb->first_page))
+        if (mutex_trylock(&eb->mutex))
                 return 0;
         for (i = 0; i < 512; i++) {
                 cpu_relax();
-                if (!TestSetPageLocked(eb->first_page))
+                if (mutex_trylock(&eb->mutex))
                         return 0;
         }
         cpu_relax();
-        lock_page(eb->first_page);
+        mutex_lock(&eb->mutex);
         return 0;
 }
 
 int btrfs_try_tree_lock(struct extent_buffer *eb)
 {
-        return TestSetPageLocked(eb->first_page);
+        return mutex_trylock(&eb->mutex);
 }
 
 int btrfs_tree_unlock(struct extent_buffer *eb)
 {
-        WARN_ON(!PageLocked(eb->first_page));
-        unlock_page(eb->first_page);
+        mutex_unlock(&eb->mutex);
         return 0;
 }
 
 int btrfs_tree_locked(struct extent_buffer *eb)
 {
-        return PageLocked(eb->first_page);
+        return mutex_is_locked(&eb->mutex);
 }