xfs: use xfs_sync_inodes() for device flushing

Currently xfs_device_flush calls sync_blockdev() which is
a no-op for XFS as all it's metadata is held in a different
address to the one sync_blockdev() works on.

Call xfs_sync_inodes() instead to flush all the delayed
allocation blocks out. To do this as efficiently as possible,
do it via two passes - one to do an async flush of all the
dirty blocks and a second to wait for all the IO to complete.
This requires some modification to the xfs-sync_inodes_ag()
flush code to do efficiently.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index 04f058c..ec95e26 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -21,18 +21,19 @@
 struct xfs_mount;
 struct xfs_perag;
 
-typedef struct bhv_vfs_sync_work {
+typedef struct xfs_sync_work {
 	struct list_head	w_list;
 	struct xfs_mount	*w_mount;
 	void			*w_data;	/* syncer routine argument */
 	void			(*w_syncer)(struct xfs_mount *, void *);
-} bhv_vfs_sync_work_t;
+} xfs_sync_work_t;
 
 #define SYNC_ATTR		0x0001	/* sync attributes */
 #define SYNC_DELWRI		0x0002	/* look at delayed writes */
 #define SYNC_WAIT		0x0004	/* wait for i/o to complete */
 #define SYNC_BDFLUSH		0x0008	/* BDFLUSH is calling -- don't block */
 #define SYNC_IOWAIT		0x0010  /* wait for all I/O to complete */
+#define SYNC_TRYLOCK		0x0020  /* only try to lock inodes */
 
 int xfs_syncd_init(struct xfs_mount *mp);
 void xfs_syncd_stop(struct xfs_mount *mp);
@@ -44,7 +45,7 @@
 void xfs_quiesce_attr(struct xfs_mount *mp);
 
 void xfs_flush_inode(struct xfs_inode *ip);
-void xfs_flush_device(struct xfs_inode *ip);
+void xfs_flush_inodes(struct xfs_inode *ip);
 
 int xfs_reclaim_inode(struct xfs_inode *ip, int locked, int sync_mode);
 int xfs_reclaim_inodes(struct xfs_mount *mp, int noblock, int mode);