[PATCH] fix handling of ext2 allocation failures

Patch from: Hugh Dickins <hugh@veritas.com>

For almost a year (since 2.5.4) ext2_new_block has tended to set err 0
instead of -ENOSPC or -EIO.  This manifested variously (typically depends on
what's stale in ext2_get_block's chain[4] array): sometimes __brelse free
free buffer backtraces, sometimes release_pages oops, usually
generic_make_request beyond end of device messages, followed by further ext2
errors.

[Insert lecture on dangers of using goto for unwind :-]

fs/ext2/balloc.c

@@ -470,10 +470,10 @@ int ext2_new_block (struct inode * inode, unsigned long goal,
 
 	ext2_debug ("allocating block %d. ", block);
 
+	*err = 0;
 out_release:
 	group_release_blocks(desc, gdp_bh, group_alloc);
 	release_blocks(sb, es_alloc);
-	*err = 0;
 out_unlock:
 	unlock_super (sb);
 	DQUOT_FREE_BLOCK(inode, dq_alloc);