[PATCH] f2fs: mutex can't be used by down_write_nest_lock()

From: Yang Shi
Date: Fri Feb 26 2016 - 19:49:07 EST

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);
fs/f2fs/f2fs.h:27:55: note: in definition of macro 'f2fs_down_write'
#define f2fs_down_write(x, y) down_write_nest_lock(x, y)
In file included from include/linux/rwsem.h:22:0,
from fs/f2fs/xattr.c:21:
include/linux/rwsem_rt.h:138:20: note: expected 'struct rw_semaphore *' but argument is of type 'struct mutex *'
static inline void down_write_nest_lock(struct rw_semaphore *sem,

Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx>
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 ff79054..af77c1a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -25,7 +25,6 @@

#define f2fs_bug_on(sbi, condition) BUG_ON(condition)
-#define f2fs_down_write(x, y) down_write_nest_lock(x, y)
#define f2fs_bug_on(sbi, condition) \
do { \
@@ -34,7 +33,6 @@
set_sbi_flag(sbi, SBI_NEED_FSCK); \
} \
} while (0)
-#define f2fs_down_write(x, y) down_write(x)

@@ -1006,7 +1004,7 @@ 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)