From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Marczykowski Subject: Re: block backend issues Date: Fri, 15 Jun 2012 13:14:12 +0200 Message-ID: <4FDB1904.6010303@invisiblethingslab.com> References: <4FD1F9E8.20508@invisiblethingslab.com> <4FD9D8A0.1060504@invisiblethingslab.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8415861635709727201==" Return-path: In-Reply-To: <4FD9D8A0.1060504@invisiblethingslab.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============8415861635709727201== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig14F5AF568E6D184B5C199126" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig14F5AF568E6D184B5C199126 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 14.06.2012 14:27, Marek Marczykowski wrote: > On 08.06.2012 15:11, Marek Marczykowski wrote: >> Hey, >> >> I've faced strange problem with block devices. When trying to read som= e file >> (from read-only ext3), everything looks good, except that file content= is >> corrupted! But this can be coincidence (that "failed" reads doesn't hi= t >> filesystem metadata). >> fsck in dom0 on filesystem image returns no errors. >> fsck (with -nf flags) in domU on the device causes the kernel to outpu= t >> "blkfront: flush disk cache: empty write xvdd op failed", "blkfront: x= vdd: >> barrier or flush: disable". And returns no filesystem errors. From tha= t point, >> file reads return correct file content. For most cases dropping block = cache >> (echo 3 > /proc/sys/vm/drop_caches) or remounting device also "fixes" = the problem. >> >> On RW device (with different size, filesystem and content), domU kerne= l >> complains about EXT4 errors. >> Doesn't observed such strange issues on device-mapper backed devices. >> >> On 3.2.7 it worked, problem observed on 3.3.5 and 3.4 in dom0, regardl= ess of >> domU kernel (tried 3.2.7, 3.3.5, 3.4.0). >> >> I've suspected feature-flush-cache/feature-barrier, but when disabled = its >> advertise in blkback code, problem still occurs. >> >> Some details: >> dom0: 3.4.0-1.pvops.qubes.x86_64 (vanilla 3.4 + Konrad's patches for A= CPI S3) >> domU: 3.3.5-1.pvops.qubes.x86_64 (vanilla 3.3.5 + Konrad's patches for= ACPI S3) >=20 > (...) > Still the case on 3.4.1 with applied patches from Konrad's for-jens-3.5= branch. > I've compared file contents and it differs in (multiply of) 1024 bytes = - the > same as filesystem block size. And only if block wasn't in pagecache in= dom0. > When I flush VM pagecache (echo 1 > /proc/.../drop_caches) after trying= to > read some files (actually md5sum -c), but not dom0 pagecache - problem > vanished. But if I clean also dom0 pagecache - problem returns. >=20 > Any clues welcomed... Ok, found the reason. It wasn't blkback fault, even on baremetal, loopback-mounted image had the same problem. It was caused by "0fc9d104 radix-tree: use iterators in find_get_pages* functions" commit somehow be= tween 3.3 and 3.4. It is already fixed in 3.4.2. --=20 Best Regards / Pozdrawiam, Marek Marczykowski Invisible Things Lab --------------enig14F5AF568E6D184B5C199126 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJP2xkEAAoJENuP0xzK19cs8YgH/idnTlU5mm1Kn0gwFdXt1h/P 7cIL+zIwyWmgUeYZK0gwDe/0BYdEE5n16lJZ//HKagEgB7gw9cEMl3OGqQAO4eE6 +y+fX2KHsqETCUscNdq44aVyBQQ2EXyundA5JvTWTph2fnyfqd93S29Agu/SHiLP oPQh2o5WGRX/mYCkb1GpnplMaDjLkhGFpeF75fxekMWc6IzV7hJUnn7IHX6ik9Yw se9ukC85GUfWWsJ+eC5MbC1Lr+FZ3d5Nk9j1lye65Re4hla/6sexG4nx19oH3xQT EaFMhSLsmunix3r+GtcNMUB9mGTlhRoiasJH+bipvLxujYCIi3ZRdTm4EpPhQOI= =gXWX -----END PGP SIGNATURE----- --------------enig14F5AF568E6D184B5C199126-- --===============8415861635709727201== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============8415861635709727201==--