I did some btrfs RTFS over the weeking and I have a hard time understanding
what this code is attempting to do:
28 int btrfs_tree_lock(struct extent_buffer *eb)
29 {
30 int i;
31
32 if (mutex_trylock(&eb->mutex))
33 return 0;
34 for (i = 0; i < 512; i++) {
35 cpu_relax();
36 if (mutex_trylock(&eb->mutex))
37 return 0;
38 }
39 cpu_relax();
40 mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(e b));
41 return 0;
42 }
The trylocks seem pretty pointless.
I presume it can be all replaced with the mutex_lock_nested() in line 40.
Also the return value seems pointless because noone checks it. Like
in the appended patch. Or do I miss something?
---
Remove unneeded trylocking and unused return value in btrfs_tree_lock
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
diff -r 417d87e57364 locking.c
--- a/locking.c Wed Aug 20 13:39:41 2008 -0400
+++ b/locking.c Mon Sep 08 13:09:21 2008 +0200
@@ -25,20 +25,9 @@
#include "extent_io.h"
#include "locking.h"
-int btrfs_tree_lock(struct extent_buffer *eb)
+void btrfs_tree_lock(struct extent_buffer *eb)
{
- int i;
-
- if (mutex_trylock(&eb->mutex))
- return 0;
- for (i = 0; i < 512; i++) {
- cpu_relax();
- if (mutex_trylock(&eb->mutex))
- return 0;
- }
- cpu_relax();
mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
- return 0;
}
int btrfs_try_tree_lock(struct extent_buffer *eb)
diff -r 417d87e57364 locking.h
--- a/locking.h Wed Aug 20 13:39:41 2008 -0400
+++ b/locking.h Mon Sep 08 13:09:21 2008 +0200
@@ -19,7 +19,7 @@
#ifndef __BTRFS_LOCKING_
#define __BTRFS_LOCKING_
-int btrfs_tree_lock(struct extent_buffer *eb);
+void btrfs_tree_lock(struct extent_buffer *eb);
int btrfs_tree_unlock(struct extent_buffer *eb);
int btrfs_tree_locked(struct extent_buffer *eb);
int btrfs_try_tree_lock(struct extent_buffer *eb);
--
ak@xxxxxxxxxxxxxxx
--
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