f2fs: support fault injection to f2fs_trylock_op()

f2fs: support fault injection for f2fs_trylock_op()

This patch supports to inject fault into f2fs_trylock_op().

Usage:
a) echo 65536 > /sys/fs/f2fs/<dev>/inject_type or
b) mount -o fault_type=65536 <dev> <mountpoint>

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a9ed2fd..8601d5e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -56,6 +56,7 @@ enum {
 	FAULT_WRITE_IO,
 	FAULT_SLAB_ALLOC,
 	FAULT_DQUOT_INIT,
+	FAULT_LOCK_OP,
 	FAULT_MAX,
 };
 
@@ -2095,6 +2096,10 @@ static inline void f2fs_lock_op(struct f2fs_sb_info *sbi)
 
 static inline int f2fs_trylock_op(struct f2fs_sb_info *sbi)
 {
+	if (time_to_inject(sbi, FAULT_LOCK_OP)) {
+		f2fs_show_injection_info(sbi, FAULT_LOCK_OP);
+		return 0;
+	}
 	return down_read_trylock(&sbi->cp_rwsem);
 }