fs/ufs: get rid of write_super

This patch makes UFS stop using the VFS '->write_super()' method along with
the 's_dirt' superblock flag, because they are on their way out.

The way we implement this is that we schedule a delay job instead relying on
's_dirt' and '->write_super()'.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and
writes out all dirty superblocks using the '->write_super()' call-back.  But the
problem with this thread is that it wastes power by waking up the system every
5 seconds, even if there are no diry superblocks, or there are no client
file-systems which would need this (e.g., btrfs does not use
'->write_super()'). So we want to kill it completely and thus, we need to make
file-systems to stop using the '->write_super()' VFS service, and then remove
it together with the kernel thread.

Tested using fsstress from the LTP project.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/ufs/ufs_fs.h b/fs/ufs/ufs_fs.h
index 8aba544..0cbd5d3 100644
--- a/fs/ufs/ufs_fs.h
+++ b/fs/ufs/ufs_fs.h
@@ -34,6 +34,7 @@
 #include <linux/kernel.h>
 #include <linux/stat.h>
 #include <linux/fs.h>
+#include <linux/workqueue.h>
 
 #include <asm/div64.h>
 typedef __u64 __bitwise __fs64;