From: Andrew Morton Subject: Re: [PATCH] ext34: ensure do_split leaves enough free space in both blocks Date: Mon, 17 Sep 2007 13:30:20 -0700 Message-ID: <20070917133020.5fc4650c.akpm@linux-foundation.org> References: <46EEA5F4.3030806@redhat.com> <46EEB7A4.9040903@sandeen.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , ext4 development , Linux Kernel Mailing List , hooanon05@yahoo.co.jp, "Theodore Ts'o" To: Eric Sandeen Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:55423 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753842AbXIQUak (ORCPT ); Mon, 17 Sep 2007 16:30:40 -0400 In-Reply-To: <46EEB7A4.9040903@sandeen.net> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Mon, 17 Sep 2007 12:21:40 -0500 Eric Sandeen wrote: > Eric Sandeen wrote: > > The do_split() function for htree dir blocks is intended to split a > > leaf block to make room for a new entry. It sorts the entries in the > > original block by hash value, then moves the last half of the entries to > > the new block - without accounting for how much space this actually moves. > > (IOW, it moves half of the entry *count* not half of the entry *space*). > > If by chance we have both large & small entries, and we move only the > > smallest entries, and we have a large new entry to insert, we may not have > > created enough space for it. > > (btw, the upshot of this is that in add_dirent_to_buf(), > memcpy(de->name, name, namelen) will overshoot the buffer and actually > corrupt memory.) Nice! So this looks like 2.6.22 and 2.6.23 material, but the timing is getting pretty squeezy. Could people please give this change an extra-close review, let me know? Thanks.