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, 5 insertions, 0 deletions

diff --git a/fs/ufs/ufs.h b/fs/ufs/ufs.h
index 528750b7e701..343e6fc571e5 100644
--- a/fs/ufs/ufs.h
+++ b/fs/ufs/ufs.h
@@ -20,6 +20,10 @@ struct ufs_sb_info {
 	unsigned s_mount_opt;
 	struct mutex mutex;
 	struct task_struct *mutex_owner;
+	struct super_block *sb;
+	int work_queued; /* non-zero if the delayed work is queued */
+	struct delayed_work sync_work; /* FS sync delayed work */
+	spinlock_t work_lock; /* protects sync_work and work_queued */
 };
 
 struct ufs_inode_info {
@@ -123,6 +127,7 @@ extern __printf(3, 4)
 void ufs_error(struct super_block *, const char *, const char *, ...);
 extern __printf(3, 4)
 void ufs_panic(struct super_block *, const char *, const char *, ...);
+void ufs_mark_sb_dirty(struct super_block *sb);
 
 /* symlink.c */
 extern const struct inode_operations ufs_fast_symlink_inode_operations;