From: Jon Nelson Subject: Re: hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt barrier support is effective) Date: Tue, 7 Dec 2010 14:36:31 -0600 Message-ID: References: <4CF692D1.1010906@redhat.com> <4CF6B3E8.2000406@redhat.com> <20101201212310.GA15648@redhat.com> <20101204193828.GB13871@redhat.com> <20101207142145.GA27861@think> <20101207182243.GB21112@redhat.com> <1291747731-sup-3099@think> <1291751698-sup-9297@think> <1291753963-sup-6290@think> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Mike Snitzer , Matt , Milan Broz , Andi Kleen , linux-btrfs , dm-devel , Linux Kernel , htd , htejun , linux-ext4 To: Chris Mason Return-path: Received: from mail-bw0-f66.google.com ([209.85.214.66]:48748 "EHLO mail-bw0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754468Ab0LGUgx convert rfc822-to-8bit (ORCPT ); Tue, 7 Dec 2010 15:36:53 -0500 In-Reply-To: <1291753963-sup-6290@think> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Dec 7, 2010 at 2:33 PM, Chris Mason wr= ote: > Excerpts from Jon Nelson's message of 2010-12-07 15:25:47 -0500: >> On Tue, Dec 7, 2010 at 2:02 PM, Chris Mason = wrote: >> > Excerpts from Jon Nelson's message of 2010-12-07 14:34:40 -0500: >> >> On Tue, Dec 7, 2010 at 12:52 PM, Chris Mason wrote: >> >> >> postgresql errors. Typically, header corruption but from the l= imited >> >> >> visibility I've had into this via strace, what I see is zeroed= pages >> >> >> where there shouldn't be. >> >> > >> >> > This sounds a lot like a bug higher up than dm-crypt. =C2=A0Zer= os tend to >> >> > come from some piece of code explicitly filling a page with zer= os, and >> >> > that often happens in the corner cases for O_DIRECT and a few o= ther >> >> > places in the filesystem. >> >> > >> >> > Have you tried triggering this with a regular block device? >> >> >> >> I just tried the whole set of tests, but with /dev/sdb directly (= as >> >> ext4) without any crypt-y bits. >> >> It takes more iterations but out of 6 tests I had one failure: sa= me >> >> type of thing, 'invalid page header in block ....'. >> >> >> >> I can't guarantee that it is a full-page of zeroes, just what I s= aw >> >> from the (limited) stracing I did. >> > >> > Fantastic. Now for our usual suspects: >> > >> > 1) Is postgres using O_DIRECT? =C2=A0If yes, please turn it off >> >> According to strace, O_DIRECT didn't show up once during the test. >> >> > 2) Is postgres allocating sparse files? =C2=A0If yes, please have = it fully >> > allocate the file instead. >> >> That's a tough one. I don't think postgresql does that, but I'm not = an >> expert here. >> >> > 3) Is postgres using preallocation (fallocate)? =C2=A0If yes, plea= se have it >> > fully allocate the file instead >> >> As far as strace is concerned, postgreql is not using fallocate in >> this version. > > Well, the only other usual suspect would be mmap. =C2=A0Does the stra= ce show > that you're using read/write for file IO or is it doing a lot of mmap= s > on the files? I'm pretty sure postgresql uses regular file I/O and not mmap. --=20 Jon -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html