[PATCH] qemu: domfsinfo should print a target name on s390x, not a complete device path
While fixing domfsinfo for non-PCI (i.e. CCW) devices on s390x, I accidentally used the whole device path for the devAlias field. However, it should only contain the base target name. Currently we have the wrong output: $ virsh domfsinfo guestname Mountpoint Name Type Target --------------------------------------- / sda3 xfs /dev/sda3 /boot sda1 xfs /dev/sda1 It should look like this instead: $ virsh domfsinfo guestname Mountpoint Name Type Target ------------------------------------ / sda3 xfs sda /boot sda1 xfs sda Thus we have to strip the "/dev/" prefix and the partition number from the string. Fixes: f8333b3b0a ("qemu: Fix domfsinfo for non-PCI device information ...") Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1858771 Reported-by: Sebastian Mitterle <smitterl@redhat.com> --- src/qemu/qemu_driver.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 05f8eb2cb7..d92bee1d35 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -18874,6 +18874,30 @@ qemuDomainGetFSInfoAgent(virQEMUDriverPtr driver, return ret; } +/* Turn device node string like "/dev/vda1" into a target name like "vda" */ +static char * +qemuAgentDevNodeToTarget(const char *devnode) +{ + char *str = g_strdup(devnode); + size_t len = strlen(str); + + /* Remove the "/dev/" prefix from the string */ + if (g_str_has_prefix(str, "/dev/")) { + len -= 5; + memmove(str, str + 5, len + 1); + } + + /* Remove the partition number from the end of the string */ + while (len > 0) { + len--; + if (!g_ascii_isdigit(str[len])) + break; + str[len] = 0; + } + + return str; +} + static virDomainFSInfoPtr qemuAgentFSInfoToPublic(qemuAgentFSInfoPtr agent, virDomainDefPtr vmdef) @@ -18903,7 +18927,7 @@ qemuAgentFSInfoToPublic(qemuAgentFSInfoPtr agent, if (diskDef != NULL) ret->devAlias[i] = g_strdup(diskDef->dst); else if (agentdisk->devnode != NULL) - ret->devAlias[i] = g_strdup(agentdisk->devnode); + ret->devAlias[i] = qemuAgentDevNodeToTarget(agentdisk->devnode); else VIR_DEBUG("Missing devnode name for '%s'.", ret->mountpoint); } -- 2.18.4
On Thu, Nov 12, 2020 at 23:48:02 +0100, Thomas Huth wrote:
While fixing domfsinfo for non-PCI (i.e. CCW) devices on s390x, I accidentally used the whole device path for the devAlias field. However, it should only contain the base target name.
Currently we have the wrong output:
$ virsh domfsinfo guestname Mountpoint Name Type Target --------------------------------------- / sda3 xfs /dev/sda3 /boot sda1 xfs /dev/sda1
It should look like this instead:
$ virsh domfsinfo guestname Mountpoint Name Type Target ------------------------------------ / sda3 xfs sda /boot sda1 xfs sda
Thus we have to strip the "/dev/" prefix and the partition number from the string.
This is not the correct approach. While our "target" looks suspiciously close to the guest /dev/name it can't be guaranteed to be the same. Stripping prefix and suffix may work in many cases, but if you want to uphold what's written in the API docs this won't be always correct. I think we need to just relax the documentation of 'virsh domfsinfo' and report the path as we do now if the s390x platform is unable to report back any information which would allow us to match the device otherwise.
Fixes: f8333b3b0a ("qemu: Fix domfsinfo for non-PCI device information ...") Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1858771 Reported-by: Sebastian Mitterle <smitterl@redhat.com> --- src/qemu/qemu_driver.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 05f8eb2cb7..d92bee1d35 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -18874,6 +18874,30 @@ qemuDomainGetFSInfoAgent(virQEMUDriverPtr driver, return ret; }
+/* Turn device node string like "/dev/vda1" into a target name like "vda" */ +static char * +qemuAgentDevNodeToTarget(const char *devnode) +{ + char *str = g_strdup(devnode); + size_t len = strlen(str); + + /* Remove the "/dev/" prefix from the string */ + if (g_str_has_prefix(str, "/dev/")) { + len -= 5; + memmove(str, str + 5, len + 1); + } + + /* Remove the partition number from the end of the string */ + while (len > 0) { + len--; + if (!g_ascii_isdigit(str[len])) + break; + str[len] = 0;
Note that the guest-reported partition name does not necessarily match what's configured in the domain XML, so this algorithm is not correct.
+ } + + return str; +} + static virDomainFSInfoPtr qemuAgentFSInfoToPublic(qemuAgentFSInfoPtr agent, virDomainDefPtr vmdef) @@ -18903,7 +18927,7 @@ qemuAgentFSInfoToPublic(qemuAgentFSInfoPtr agent, if (diskDef != NULL) ret->devAlias[i] = g_strdup(diskDef->dst); else if (agentdisk->devnode != NULL) - ret->devAlias[i] = g_strdup(agentdisk->devnode); + ret->devAlias[i] = qemuAgentDevNodeToTarget(agentdisk->devnode); else VIR_DEBUG("Missing devnode name for '%s'.", ret->mountpoint); } -- 2.18.4
On 13/11/2020 08.21, Peter Krempa wrote:
On Thu, Nov 12, 2020 at 23:48:02 +0100, Thomas Huth wrote:
While fixing domfsinfo for non-PCI (i.e. CCW) devices on s390x, I accidentally used the whole device path for the devAlias field. However, it should only contain the base target name.
Currently we have the wrong output:
$ virsh domfsinfo guestname Mountpoint Name Type Target --------------------------------------- / sda3 xfs /dev/sda3 /boot sda1 xfs /dev/sda1
It should look like this instead:
$ virsh domfsinfo guestname Mountpoint Name Type Target ------------------------------------ / sda3 xfs sda /boot sda1 xfs sda
Thus we have to strip the "/dev/" prefix and the partition number from the string.
This is not the correct approach. While our "target" looks suspiciously close to the guest /dev/name it can't be guaranteed to be the same.
Ouch, ok, got it now. On x86, I can apparently say: <target dev='vdc' bus='virtio'/> for my first disk of my guest, and domfsinfo then shows up like this: Mountpoint Name Type Target ----------------------------------------------------------- / dm-0 xfs vdc /boot vda1 xfs vdc ... very confusing if you're not used to it ;-)
Stripping prefix and suffix may work in many cases, but if you want to uphold what's written in the API docs this won't be always correct.
I think we need to just relax the documentation of 'virsh domfsinfo' and report the path as we do now if the s390x platform is unable to report back any information which would allow us to match the device otherwise.
Ok, I'll ponder about this for a while - maybe there's a way to fix this on s390x ... otherwise I'll consider sending a patch to update the docs. Thanks, Thomas
participants (2)
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Peter Krempa -
Thomas Huth