[PATCH RT 19/22] f2fs: Mutex cant be used by down_write_nest_lock()

[Steven Rostedt]

4.1.15-rt18-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Yang Shi <yang.shi@xxxxxxxxxx>

fsf2_lock_all() calls down_write_nest_lock() to acquire a rw_sem and check
a mutex, but down_write_nest_lock() is designed for two rw_sem accoring to the
comment in include/linux/rwsem.h. And, other than f2fs, it is just called in
mm/mmap.c with two rwsem.

So, it looks it is used wrongly by f2fs. And, it causes the below compile
warning on -rt kernel too.

In file included from fs/f2fs/xattr.c:25:0:
fs/f2fs/f2fs.h: In function 'f2fs_lock_all':
fs/f2fs/f2fs.h:962:34: warning: passing argument 2 of 'down_write_nest_lock' from
		       incompatible pointer type [-Wincompatible-pointer-types]
  f2fs_down_write(&sbi->cp_rwsem, &sbi->cp_mutex);
                                  ^

The nest annotation was anyway bogus as nested annotations for lockdep are
only required if one nests two locks of the same lock class, which is not the
case here.

Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx>
Cc: cm224.lee@xxxxxxxxxxx
Cc: chao2.yu@xxxxxxxxxxx
Cc: linaro-kernel@xxxxxxxxxxxxxxxx
Cc: linux-rt-users@xxxxxxxxxxxxxxx
Cc: bigeasy@xxxxxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: jaegeuk@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1456532725-4126-1-git-send-email-yang.shi@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 fs/f2fs/f2fs.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8de34ab6d5b1..4e80270703a4 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -22,7 +22,6 @@
 
 #ifdef CONFIG_F2FS_CHECK_FS
 #define f2fs_bug_on(sbi, condition)	BUG_ON(condition)
-#define f2fs_down_write(x, y)	down_write_nest_lock(x, y)
 #else
 #define f2fs_bug_on(sbi, condition)					\
 	do {								\
@@ -31,7 +30,6 @@
 			set_sbi_flag(sbi, SBI_NEED_FSCK);		\
 		}							\
 	} while (0)
-#define f2fs_down_write(x, y)	down_write(x)
 #endif
 
 /*
@@ -838,7 +836,7 @@ static inline void f2fs_unlock_op(struct f2fs_sb_info *sbi)
 
 static inline void f2fs_lock_all(struct f2fs_sb_info *sbi)
 {
-	f2fs_down_write(&sbi->cp_rwsem, &sbi->cp_mutex);
+	down_write(&sbi->cp_rwsem);
 }
 
 static inline void f2fs_unlock_all(struct f2fs_sb_info *sbi)
-- 
2.7.0