f2fs: rename dio_rwsem to i_gc_rwsem

RW semphore dio_rwsem in struct f2fs_inode_info is introduced to avoid
race between dio and data gc, but now, it is more wildly used to avoid
foreground operation vs data gc. So rename it to i_gc_rwsem to improve
its readability.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c2d1208..7d19fd0 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -653,7 +653,9 @@ struct f2fs_inode_info {
 	struct task_struct *inmem_task;	/* store inmemory task */
 	struct mutex inmem_lock;	/* lock for inmemory pages */
 	struct extent_tree *extent_tree;	/* cached extent_tree entry */
-	struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
+
+	/* avoid racing between foreground op and gc */
+	struct rw_semaphore i_gc_rwsem[2];
 	struct rw_semaphore i_mmap_sem;
 	struct rw_semaphore i_xattr_sem; /* avoid racing between reading and changing EAs */