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>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 62cee2b..bb0f776 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1127,7 +1127,8 @@
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 @@
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 */