From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Marczykowski Subject: Re: block backend issues Date: Thu, 14 Jun 2012 14:27:12 +0200 Message-ID: <4FD9D8A0.1060504@invisiblethingslab.com> References: <4FD1F9E8.20508@invisiblethingslab.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2254790533967183525==" Return-path: In-Reply-To: <4FD1F9E8.20508@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) --===============2254790533967183525== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig5921C7AAF3C6B88F38892638" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig5921C7AAF3C6B88F38892638 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 08.06.2012 15:11, Marek Marczykowski wrote: > Hey, >=20 > I've faced strange problem with block devices. When trying to read some= file > (from read-only ext3), everything looks good, except that file content = is > corrupted! But this can be coincidence (that "failed" reads doesn't hit= > filesystem metadata). > fsck in dom0 on filesystem image returns no errors. > fsck (with -nf flags) in domU on the device causes the kernel to output= > "blkfront: flush disk cache: empty write xvdd op failed", "blkfront: xv= dd: > barrier or flush: disable". And returns no filesystem errors. From that= point, > file reads return correct file content. For most cases dropping block c= ache > (echo 3 > /proc/sys/vm/drop_caches) or remounting device also "fixes" t= he problem. >=20 > On RW device (with different size, filesystem and content), domU kernel= > complains about EXT4 errors. > Doesn't observed such strange issues on device-mapper backed devices. >=20 > On 3.2.7 it worked, problem observed on 3.3.5 and 3.4 in dom0, regardle= ss of > domU kernel (tried 3.2.7, 3.3.5, 3.4.0). >=20 > I've suspected feature-flush-cache/feature-barrier, but when disabled i= ts > advertise in blkback code, problem still occurs. >=20 > Some details: > dom0: 3.4.0-1.pvops.qubes.x86_64 (vanilla 3.4 + Konrad's patches for AC= PI S3) > domU: 3.3.5-1.pvops.qubes.x86_64 (vanilla 3.3.5 + Konrad's patches for = ACPI S3) (...) Still the case on 3.4.1 with applied patches from Konrad's for-jens-3.5 b= ranch. 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 d= om0. When I flush VM pagecache (echo 1 > /proc/.../drop_caches) after trying t= o read some files (actually md5sum -c), but not dom0 pagecache - problem vanished. But if I clean also dom0 pagecache - problem returns. Any clues welcomed... --=20 Best Regards / Pozdrawiam, Marek Marczykowski Invisible Things Lab --------------enig5921C7AAF3C6B88F38892638 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/ iQEcBAEBAgAGBQJP2dihAAoJENuP0xzK19csfaoH/0Ml1lyBHNoYMbwdtXhNgvfE VccjdwSj4hlNSLuv1nO+lma9LgPh2cgkKhKKj//Exie3ijHJnCxqpkezWTnmYvh9 fu5GzAyrp3k+lV8e62fenOQ2nGWoEQWERlu7iDRj/RL+rmzAzpbiUpGpciANyFXB z6lzd12/1ciV8JZcKgeY4nOCR49kJic6NnfVusDGqia9VLn+l5ej3aoM231wzJwg yVnXWM+ysXKZeEe33QciRdKyhWWkDXGxTen+rbpTdFz5M529DCjn/RSAM6lh6bBF QBCaUkw6u6ve0fGx+FGuuP3ZoA7MweVaZb6rBizIj+JID1ZwHl4DiyhomffXsM4= =0N32 -----END PGP SIGNATURE----- --------------enig5921C7AAF3C6B88F38892638-- --===============2254790533967183525== 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 --===============2254790533967183525==--