vfs: Make sys_sync() use fsync_super() (version 4)

It is unnecessarily fragile to have two places (fsync_super() and do_sync())
doing data integrity sync of the filesystem. Alter __fsync_super() to
accommodate needs of both callers and use it. So after this patch
__fsync_super() is the only place where we gather all the calls needed to
properly send all data on a filesystem to disk.

Nice bonus is that we get a complete livelock avoidance and write_supers()
is now only used for periodic writeback of superblocks.

sync_blockdevs() introduced a couple of patches ago is gone now.

[build fixes folded]

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 1 insertions, 2 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 41a9907f342..f00df653cf2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1321,7 +1321,7 @@ struct super_block {
         struct rw_semaphore     s_umount;
         struct mutex            s_lock;
         int                     s_count;
-        int                     s_need_sync_fs;
+        int                     s_need_sync;
         atomic_t                s_active;
 #ifdef CONFIG_SECURITY
         void                    *s_security;
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 93445477f86..3224820c851 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -79,7 +79,6 @@ struct writeback_control {
 void writeback_inodes(struct writeback_control *wbc);
 int inode_wait(void *);
 void sync_inodes_sb(struct super_block *, int wait);
-void sync_inodes(int wait);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */
 static inline void wait_on_inode(struct inode *inode)