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, 12 insertions, 4 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index bd50b11..8f2271a 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -905,21 +905,29 @@ EXPORT_SYMBOL_GPL(generic_fh_to_parent);
  * filesystems which track all non-inode metadata in the buffers list
  * hanging off the address_space structure.
  */
-int generic_file_fsync(struct file *file, int datasync)
+int generic_file_fsync(struct file *file, loff_t start, loff_t end,
+		       int datasync)
 {
 	struct inode *inode = file->f_mapping->host;
 	int err;
 	int ret;
 
+	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (err)
+		return err;
+
+	mutex_lock(&inode->i_mutex);
 	ret = sync_mapping_buffers(inode->i_mapping);
 	if (!(inode->i_state & I_DIRTY))
-		return ret;
+		goto out;
 	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
-		return ret;
+		goto out;
 
 	err = sync_inode_metadata(inode, 1);
 	if (ret == 0)
 		ret = err;
+out:
+	mutex_unlock(&inode->i_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(generic_file_fsync);
@@ -956,7 +964,7 @@ EXPORT_SYMBOL(generic_check_addressable);
 /*
  * No-op implementation of ->fsync for in-memory filesystems.
  */
-int noop_fsync(struct file *file, int datasync)
+int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	return 0;
 }