[XFS] Warn if errors come from block_truncate_page().

block_truncate_page() can return errors that we currently ignore and
silently discard. We should not ever get errors reported here - an error
indicates a bug somewhere else. Hence catch the error and issue a stack
dump to the syslog because we cannot propagate the error any further up
the call chain.

SGI-PV: 980084
SGI-Modid: xfs-linux-melb:xfs-kern:30800a
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Niv Sardi <xaiki@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/linux-2.6/xfs_iops.c

@@ -692,11 +692,19 @@ xfs_vn_setattr(
 	return -error;
 }
 
+/*
+ * block_truncate_page can return an error, but we can't propagate it
+ * at all here. Leave a complaint + stack trace in the syslog because
+ * this could be bad. If it is bad, we need to propagate the error further.
+ */
 STATIC void
 xfs_vn_truncate(
 	struct inode	*inode)
 {
-	block_truncate_page(inode->i_mapping, inode->i_size, xfs_get_blocks);
+	int	error;
+	error = block_truncate_page(inode->i_mapping, inode->i_size,
+							xfs_get_blocks);
+	WARN_ON(error);
 }
 
 STATIC int