ext4: prevent parallel resizers by atomic bit ops

Before this patch, parallel resizers are allowed and protected by a
mutex lock, actually, there is no need to support parallel resizer, so
this patch prevents parallel resizers by atmoic bit ops, like
lock_page() and unlock_page() do.

To do this, the patch removed the mutex lock s_resize_lock from struct
ext4_sb_info and added a unsigned long field named s_resize_flags
which inidicates if there is a resizer.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 62cee2b6fe79..bb0f7760c7c8 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1127,7 +1127,8 @@ struct ext4_sb_info {
         struct journal_s *s_journal;
         struct list_head s_orphan;
         struct mutex s_orphan_lock;
-        struct mutex s_resize_lock;
+        unsigned long s_resize_flags;           /* Flags indicating if there
+                                                   is a resizer */
         unsigned long s_commit_interval;
         u32 s_max_batch_time;
         u32 s_min_batch_time;
@@ -2269,6 +2270,10 @@ static inline void set_bitmap_uptodate(struct buffer_head *bh)
 extern wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
 extern struct mutex ext4__aio_mutex[EXT4_WQ_HASH_SZ];
 
+#define EXT4_RESIZING   0
+extern int ext4_resize_begin(struct super_block *sb);
+extern void ext4_resize_end(struct super_block *sb);
+
 #endif  /* __KERNEL__ */
 
 #endif  /* _EXT4_H */