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 14:25:47 -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> 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: In-Reply-To: <1291751698-sup-9297@think> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue, Dec 7, 2010 at 2:02 PM, Chris Mason wr= ote: > 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 limi= ted >> >> visibility I've had into this via strace, what I see is zeroed pa= ges >> >> where there shouldn't be. >> > >> > This sounds a lot like a bug higher up than dm-crypt. =C2=A0Zeros = tend to >> > come from some piece of code explicitly filling a page with zeros,= and >> > that often happens in the corner cases for O_DIRECT and a few othe= r >> > 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: same >> type of thing, 'invalid page header in block ....'. >> >> I can't guarantee that it is a full-page of zeroes, just what I saw >> 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, please = have it > fully allocate the file instead As far as strace is concerned, postgreql is not using fallocate in this version. --=20 Jon