From: Dmitry Monakhov Subject: Re: [PATCH] ext4: Do not zeroout uninitialized extents beyond i_size Date: Wed, 28 Apr 2010 11:38:58 +0400 Message-ID: <871ve0qb59.fsf@openvz.org> References: <1270833748-14381-1-git-send-email-dmonakhov@openvz.org> <87och49oly.fsf@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, tytso@mit.edu To: "Aneesh Kumar K. V" Return-path: Received: from mail-bw0-f219.google.com ([209.85.218.219]:42943 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751284Ab0D1HjD (ORCPT ); Wed, 28 Apr 2010 03:39:03 -0400 Received: by bwz19 with SMTP id 19so247194bwz.21 for ; Wed, 28 Apr 2010 00:39:00 -0700 (PDT) In-Reply-To: <87och49oly.fsf@linux.vnet.ibm.com> (Aneesh Kumar K. V.'s message of "Wed, 28 Apr 2010 10:10:09 +0530") Sender: linux-ext4-owner@vger.kernel.org List-ID: "Aneesh Kumar K. V" writes: > On Fri, 9 Apr 2010 21:22:28 +0400, Dmitry Monakhov wrote: >> Zerrout trick allow us to optimize cases where it is more reasonable >> to explicitly zeroout extent and mark it as initialized instead of >> splitting to several small ones. >> But this optimization is not acceptable is extent is beyond i_size >> Because it is not possible to have initialized blocks after i_size. >> Fsck treat this as incorrect inode size. >> > > With commit c8d46e41bc744c8fa0092112af3942fcd46c8b18 if we set > EXT4_EOFBLOCKS_FL we should be able to have blocks beyond i_size. > May be the zero out path should set the flag instead of doing all these > changes. Zero-out is already complex with all the ENOSPC related > consideration. I guess we should try to keep it simple. For initialized extent beyond i_size? I've check fsck and seems that is truly possible. So this optimization allow us to avoid some bad EIO situations. But we have to rework ext_get_blocks( ,create == 1) to clear EXT4_EOFBLOCKS_FL if last block of latest_extent is requested. I'll handle this. > > -aneesh > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html