xfs: split xfs_sync_inodes

xfs_sync_inodes is used to write back either file data or inode metadata.
In general we always do these separately, except for one fishy case in
xfs_fs_put_super that does both.  So separate xfs_sync_inodes into
separate xfs_sync_data and xfs_sync_attr functions.  In xfs_fs_put_super
we first call the data sync and then the attr sync as that was the previous
order.  The moved log force in that path doesn't make a difference because
we will force the log again as part of the real unmount process.

The filesystem readonly checks are not performed by the new function but
instead moved into the callers, given that most callers alredy have it
further up in the stack.  Also add debug checks that we do not pass in
incorrect flags in the new xfs_sync_data and xfs_sync_attr function and
fix the one place that did pass in a wrong flag.

Also remove a comment mentioning xfs_sync_inodes that has been incorrect
for a while because we always take either the iolock or ilock in the
sync path these days.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index 9bb1253..26bfb5c 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -29,8 +29,6 @@
 	struct completion	*w_completion;
 } 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 */
@@ -39,7 +37,8 @@
 int xfs_syncd_init(struct xfs_mount *mp);
 void xfs_syncd_stop(struct xfs_mount *mp);
 
-int xfs_sync_inodes(struct xfs_mount *mp, int flags);
+int xfs_sync_attr(struct xfs_mount *mp, int flags);
+int xfs_sync_data(struct xfs_mount *mp, int flags);
 int xfs_sync_fsdata(struct xfs_mount *mp, int flags);
 
 int xfs_quiesce_data(struct xfs_mount *mp);