fs: push i_mutex and filemap_write_and_wait down into ->fsync() handlers

Btrfs needs to be able to control how filemap_write_and_wait_range() is called
in fsync to make it less of a painful operation, so push down taking i_mutex and
the calling of filemap_write_and_wait() down into the ->fsync() handlers.  Some
file systems can drop taking the i_mutex altogether it seems, like ext3 and
ocfs2.  For correctness sake I just pushed everything down in all cases to make
sure that we keep the current behavior the same for everybody, and then each
individual fs maintainer can make up their mind about what to do from there.
Thanks,

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 804000183c5e..32814e8800e0 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -66,19 +66,26 @@ static int fb_deferred_io_fault(struct vm_area_struct *vma,
 	return 0;
 }
 
-int fb_deferred_io_fsync(struct file *file, int datasync)
+int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct fb_info *info = file->private_data;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (err)
+		return err;
 
 	/* Skip if deferred io is compiled-in but disabled on this fbdev */
 	if (!info->fbdefio)
 		return 0;
 
+	mutex_lock(&inode->i_mutex);
 	/* Kill off the delayed work */
 	cancel_delayed_work_sync(&info->deferred_work);
 
 	/* Run it immediately */
-	return schedule_delayed_work(&info->deferred_work, 0);
+	err = schedule_delayed_work(&info->deferred_work, 0);
+	mutex_unlock(&inode->i_mutex);
+	return err;
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);