vfs: Move syncing code from super.c to sync.c (version 4)

Move sync_filesystems(), __fsync_super(), fsync_super() from
super.c to sync.c where it fits better.

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

fs/super.c

@@ -283,42 +283,6 @@ void unlock_super(struct super_block * sb)
 EXPORT_SYMBOL(lock_super);
 EXPORT_SYMBOL(unlock_super);
 
-/*
- * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
- * just dirties buffers with inodes so we have to submit IO for these buffers
- * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
- * case write_inode() functions do sync_dirty_buffer() and thus effectively
- * write one block at a time.
- */
-static int __fsync_super(struct super_block *sb, int wait)
-{
-	vfs_dq_sync(sb);
-	sync_inodes_sb(sb, wait);
-	lock_super(sb);
-	if (sb->s_dirt && sb->s_op->write_super)
-		sb->s_op->write_super(sb);
-	unlock_super(sb);
-	if (sb->s_op->sync_fs)
-		sb->s_op->sync_fs(sb, wait);
-	return __sync_blockdev(sb->s_bdev, wait);
-}
-
-/*
- * Write out and wait upon all dirty data associated with this
- * superblock.  Filesystem data as well as the underlying block
- * device.  Takes the superblock lock.
- */
-int fsync_super(struct super_block *sb)
-{
-	int ret;
-
-	ret = __fsync_super(sb, 0);
-	if (ret < 0)
-		return ret;
-	return __fsync_super(sb, 1);
-}
-EXPORT_SYMBOL_GPL(fsync_super);
-
 /**
  *	generic_shutdown_super	-	common helper for ->kill_sb()
  *	@sb: superblock to kill
@@ -473,55 +437,6 @@ void sync_supers(void)
 	spin_unlock(&sb_lock);
 }
 
-/*
- * Sync all the data for all the filesystems (called by sys_sync() and
- * emergency sync)
- *
- * This operation is careful to avoid the livelock which could easily happen
- * if two or more filesystems are being continuously dirtied.  s_need_sync
- * is used only here.  We set it against all filesystems and then clear it as
- * we sync them.  So redirtied filesystems are skipped.
- *
- * But if process A is currently running sync_filesystems and then process B
- * calls sync_filesystems as well, process B will set all the s_need_sync
- * flags again, which will cause process A to resync everything.  Fix that with
- * a local mutex.
- */
-void sync_filesystems(int wait)
-{
-	struct super_block *sb;
-	static DEFINE_MUTEX(mutex);
-
-	mutex_lock(&mutex);		/* Could be down_interruptible */
-	spin_lock(&sb_lock);
-	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (sb->s_flags & MS_RDONLY)
-			continue;
-		sb->s_need_sync = 1;
-	}
-
-restart:
-	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (!sb->s_need_sync)
-			continue;
-		sb->s_need_sync = 0;
-		if (sb->s_flags & MS_RDONLY)
-			continue;	/* hm.  Was remounted r/o meanwhile */
-		sb->s_count++;
-		spin_unlock(&sb_lock);
-		down_read(&sb->s_umount);
-		if (sb->s_root)
-			__fsync_super(sb, wait);
-		up_read(&sb->s_umount);
-		/* restart only when sb is no longer on the list */
-		spin_lock(&sb_lock);
-		if (__put_super_and_need_restart(sb))
-			goto restart;
-	}
-	spin_unlock(&sb_lock);
-	mutex_unlock(&mutex);
-}
-
 /**
  *	get_super - get the superblock of a device
  *	@bdev: device to get the superblock for

fs/sync.c

@@ -18,6 +18,91 @@
 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
 			SYNC_FILE_RANGE_WAIT_AFTER)
 
+/*
+ * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
+ * just dirties buffers with inodes so we have to submit IO for these buffers
+ * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
+ * case write_inode() functions do sync_dirty_buffer() and thus effectively
+ * write one block at a time.
+ */
+static int __fsync_super(struct super_block *sb, int wait)
+{
+	vfs_dq_sync(sb);
+	sync_inodes_sb(sb, wait);
+	lock_super(sb);
+	if (sb->s_dirt && sb->s_op->write_super)
+		sb->s_op->write_super(sb);
+	unlock_super(sb);
+	if (sb->s_op->sync_fs)
+		sb->s_op->sync_fs(sb, wait);
+	return __sync_blockdev(sb->s_bdev, wait);
+}
+
+/*
+ * Write out and wait upon all dirty data associated with this
+ * superblock.  Filesystem data as well as the underlying block
+ * device.  Takes the superblock lock.
+ */
+int fsync_super(struct super_block *sb)
+{
+	int ret;
+
+	ret = __fsync_super(sb, 0);
+	if (ret < 0)
+		return ret;
+	return __fsync_super(sb, 1);
+}
+EXPORT_SYMBOL_GPL(fsync_super);
+
+/*
+ * Sync all the data for all the filesystems (called by sys_sync() and
+ * emergency sync)
+ *
+ * This operation is careful to avoid the livelock which could easily happen
+ * if two or more filesystems are being continuously dirtied.  s_need_sync
+ * is used only here.  We set it against all filesystems and then clear it as
+ * we sync them.  So redirtied filesystems are skipped.
+ *
+ * But if process A is currently running sync_filesystems and then process B
+ * calls sync_filesystems as well, process B will set all the s_need_sync
+ * flags again, which will cause process A to resync everything.  Fix that with
+ * a local mutex.
+ */
+static void sync_filesystems(int wait)
+{
+	struct super_block *sb;
+	static DEFINE_MUTEX(mutex);
+
+	mutex_lock(&mutex);		/* Could be down_interruptible */
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (sb->s_flags & MS_RDONLY)
+			continue;
+		sb->s_need_sync = 1;
+	}
+
+restart:
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (!sb->s_need_sync)
+			continue;
+		sb->s_need_sync = 0;
+		if (sb->s_flags & MS_RDONLY)
+			continue;	/* hm.  Was remounted r/o meanwhile */
+		sb->s_count++;
+		spin_unlock(&sb_lock);
+		down_read(&sb->s_umount);
+		if (sb->s_root)
+			__fsync_super(sb, wait);
+		up_read(&sb->s_umount);
+		/* restart only when sb is no longer on the list */
+		spin_lock(&sb_lock);
+		if (__put_super_and_need_restart(sb))
+			goto restart;
+	}
+	spin_unlock(&sb_lock);
+	mutex_unlock(&mutex);
+}
+
 SYSCALL_DEFINE0(sync)
 {
 	sync_filesystems(0);

include/linux/fs.h

@@ -1942,7 +1942,6 @@ extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
 extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
 extern int fsync_bdev(struct block_device *);
-extern int fsync_super(struct super_block *);
 extern int fsync_no_super(struct block_device *);
 #else
 static inline void bd_forget(struct inode *inode) {}
@@ -1959,6 +1958,7 @@ static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 	return 0;
 }
 #endif
+extern int fsync_super(struct super_block *);
 extern const struct file_operations def_blk_fops;
 extern const struct file_operations def_chr_fops;
 extern const struct file_operations bad_sock_fops;
@@ -2077,7 +2077,6 @@ extern int filemap_fdatawrite_range(struct address_space *mapping,
 
 extern int vfs_fsync(struct file *file, struct dentry *dentry, int datasync);
 extern void sync_supers(void);
-extern void sync_filesystems(int wait);
 extern void emergency_sync(void);
 extern void emergency_remount(void);
 extern int do_remount_sb(struct super_block *sb, int flags,