From: Eric Sandeen Subject: Re: [PATCH -v2] ext4: use truncate_setsize() unconditionally Date: Tue, 24 May 2011 09:30:02 -0500 Message-ID: <4DDBC0EA.7000609@redhat.com> References: <1306178341-17632-1-git-send-email-tytso@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Ext4 Developers List , jiayingz@google.com To: "Theodore Ts'o" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:15178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756092Ab1EXOaG (ORCPT ); Tue, 24 May 2011 10:30:06 -0400 In-Reply-To: <1306178341-17632-1-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 5/23/11 2:19 PM, Theodore Ts'o wrote: > In commit c8d46e41 (ext4: Add flag to files with blocks intentionally > past EOF), if the EOFBLOCKS_FL flag is set, we call ext4_truncate() > before calling vmtruncate(). This caused any allocated but unwritten > blocks created by calling fallocate() with the FALLOC_FL_KEEP_SIZE > flag to be dropped. This was done to make to make sure that > EOFBLOCKS_FL would not be cleared while still leaving blocks past > i_size allocated. This was not necessary, since ext4_truncate() > guarantees that blocks past i_size will be dropped, even in the case > where truncate() has increased i_size before calling ext4_truncate(). > > So fix this by removing the EOFBLOCKS_FL special case treatment in > ext4_setattr(). In addition, use truncate_setsize() followed by a > call to ext4_truncate() instead of using vmtruncate(). This is more > efficient since it skips the call to inode_newsize_ok(), which has > been checked already by inode_change_ok(). This is also in a win in > the case where EOFBLOCKS_FL is set since it avoids calling > ext4_truncate() twice. > > Signed-off-by: "Theodore Ts'o" > --- > Jiayingz pointed out that in the case where we fallocate 12k, write 4k, and > then truncate to 4k, we should discard the excess fallocate'd blocks. So if > attr->ia_size == inode.i_size, we can skip the truncate_setsize() call, but > if the EOFBLOCKS_FL flag is set, we should still call ext4_truncate(). are there xfstests which cover this explicitly? It should be simple to write. If filesystem behavior differs we can always make ext4-only tests. -Eric