gfs2: Fix gfs2_file_buffered_write endless loop workaround

Since commit 554c577cee95b, gfs2_file_buffered_write() can accidentally
return a truncated iov_iter, which might confuse callers.  Fix that.

Fixes: 554c577cee95b ("gfs2: Prevent endless loops in gfs2_file_buffered_write")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/file.c

@@ -1084,6 +1084,7 @@ out_uninit:
 	gfs2_holder_uninit(gh);
 	if (statfs_gh)
 		kfree(statfs_gh);
+	from->count = orig_count - read;
 	return read ? read : ret;
 }