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, 8 insertions, 3 deletions

diff --git a/drivers/staging/pohmelfs/inode.c b/drivers/staging/pohmelfs/inode.c
index c0f0ac7c1cd..f3c6060c96b 100644
--- a/drivers/staging/pohmelfs/inode.c
+++ b/drivers/staging/pohmelfs/inode.c
@@ -887,11 +887,16 @@ static struct inode *pohmelfs_alloc_inode(struct super_block *sb)
 /*
  * We want fsync() to work on POHMELFS.
  */
-static int pohmelfs_fsync(struct file *file, int datasync)
+static int pohmelfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
         struct inode *inode = file->f_mapping->host;
-
-        return sync_inode_metadata(inode, 1);
+        int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+        if (!err) {
+                mutex_lock(&inode->i_mutex);
+                err = sync_inode_metadata(inode, 1);
+                mutex_unlock(&inode->i_mutex);
+        }
+        return err;
 }
 
 ssize_t pohmelfs_write(struct file *file, const char __user *buf,