From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Marczykowski Subject: block backend issues Date: Fri, 08 Jun 2012 15:11:04 +0200 Message-ID: <4FD1F9E8.20508@invisiblethingslab.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3773219682007729060==" Return-path: 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) --===============3773219682007729060== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigFFD4C680D67EA0F80C21907E" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigFFD4C680D67EA0F80C21907E Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hey, I've faced strange problem with block devices. When trying to read some f= ile (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: xvdd= : barrier or flush: disable". And returns no filesystem errors. From that p= oint, file reads return correct file content. For most cases dropping block cac= he (echo 3 > /proc/sys/vm/drop_caches) or remounting device also "fixes" the= problem. 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. On 3.2.7 it worked, problem observed on 3.3.5 and 3.4 in dom0, regardless= 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 ACPI= S3) domU: 3.3.5-1.pvops.qubes.x86_64 (vanilla 3.3.5 + Konrad's patches for AC= PI S3) domU: # mount | grep /lib/modules /dev/xvdd on /usr/lib/modules type ext3 (ro,relatime,errors=3Dcontinue,barrier=3D1,data=3Dordered) # pwd /lib/modules/3.3.5-1.pvops.qubes.x86_64/kernel # md5sum ./sound/usb/snd-usbmidi-lib.ko fbc0aeb4dd5c0c3b041a5899a15c6566 ./sound/usb/snd-usbmidi-lib.ko # ls -l ./sound/usb/snd-usbmidi-lib.ko -rwxr--r-- 1 root root 38248 May 20 14:14 ./sound/usb/snd-usbmidi-lib.ko dom0: # mount|grep modules /var/lib/qubes/vm-kernels/3.3.5/modules.img on /mnt/tmp type ext3 (ro,loop=3D/dev/loop10) # pwd /mnt/tmp/3.3.5-1.pvops.qubes.x86_64/kernel # md5sum ./sound/usb/snd-usbmidi-lib.ko 9d2d3fedd4a357252e367fa8109c16ed ./sound/usb/snd-usbmidi-lib.ko # ls -l ./sound/usb/snd-usbmidi-lib.ko -rwxr--r-- 1 root root 38248 May 20 14:14 ./sound/usb/snd-usbmidi-lib.ko And block backend parameters: # xenstore-ls /local/domain/0/backend/vbd/3/51760 frontend =3D "/local/domain/3/device/vbd/51760" params =3D "/var/lib/qubes/vm-kernels/3.3.5/modules.img" scripted =3D "1" frontend-id =3D "3" online =3D "1" removable =3D "0" bootable =3D "1" state =3D "4" dev =3D "xvdd" type =3D "file" mode =3D "r" node =3D "/dev/loop4" physical-device =3D "7:4" hotplug-status =3D "connected" feature-flush-cache =3D "1" discard-granularity =3D "4096" discard-alignment =3D "0" discard-secure =3D "0" feature-discard =3D "1" feature-barrier =3D "1" sectors =3D "409600" info =3D "4" sector-size =3D "512" BTW 3.2.7 advertise feature-flush-cache=3D0 and feature-barrier=3D0 on th= is one device (RO, loop backed). Don't know why, but seems irrelevant to this is= sue. --=20 Best Regards / Pozdrawiam, Marek Marczykowski Invisible Things Lab --------------enigFFD4C680D67EA0F80C21907E 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/ iQEcBAEBAgAGBQJP0fnoAAoJENuP0xzK19csX3QH/0rWMObmYSQmjXQn+LdcuAyZ FqVqDlv/2229qUMBeVfmLst6jFX2WhKuAH+WEiJSW6ZTxfpZ4uha8s4k5Nh3ARqJ rOM/lTxx7MtY19mwt0cZvdfip6UI1pV0kVH3m0vxsrL5kV30UVaCY6XlT55T1sO+ YSvkvq1MFG1EInbW2QFhQ1+rxfVRL42+tsXo7iBrvPrzwMVcfKy6BiAlDDg/lkwQ TFsKTlbesp/EATVmZRXilLh1mxTL1oGZ5pESrR0y3uJrVE+bqA1uqBgQ2UJYpTJE HSBFHEReFTrFh1y/00hR0BCQPXTFPQ/s+jsfg1GH3IwGxN+oxiyMRMpFW2uAVZQ= =Gtdx -----END PGP SIGNATURE----- --------------enigFFD4C680D67EA0F80C21907E-- --===============3773219682007729060== 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 --===============3773219682007729060==--