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, 16 insertions, 2 deletions

diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index 09b13bb..0bcf63a 100644
--- a/fs/ext3/fsync.c
+++ b/fs/ext3/fsync.c
@@ -43,7 +43,7 @@
  * inode to disk.
  */
 
-int ext3_sync_file(struct file *file, int datasync)
+int ext3_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct inode *inode = file->f_mapping->host;
 	struct ext3_inode_info *ei = EXT3_I(inode);
@@ -54,6 +54,17 @@ int ext3_sync_file(struct file *file, int datasync)
 	if (inode->i_sb->s_flags & MS_RDONLY)
 		return 0;
 
+	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (ret)
+		return ret;
+
+	/*
+	 * Taking the mutex here just to keep consistent with how fsync was
+	 * called previously, however it looks like we don't need to take
+	 * i_mutex at all.
+	 */
+	mutex_lock(&inode->i_mutex);
+
 	J_ASSERT(ext3_journal_current_handle() == NULL);
 
 	/*
@@ -70,8 +81,10 @@ int ext3_sync_file(struct file *file, int datasync)
 	 *  (they were dirtied by commit).  But that's OK - the blocks are
 	 *  safe in-journal, which is all fsync() needs to ensure.
 	 */
-	if (ext3_should_journal_data(inode))
+	if (ext3_should_journal_data(inode)) {
+		mutex_unlock(&inode->i_mutex);
 		return ext3_force_commit(inode->i_sb);
+	}
 
 	if (datasync)
 		commit_tid = atomic_read(&ei->i_datasync_tid);
@@ -91,5 +104,6 @@ int ext3_sync_file(struct file *file, int datasync)
 	 */
 	if (needs_barrier)
 		blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
+	mutex_unlock(&inode->i_mutex);
 	return ret;
 }