[libvirt] [PATCH] disk: Fixup error handling path for devmapper when part_separator='yes'

[Martin Kletzander]

On Thu, Nov 17, 2016 at 09:55:06AM -0500, John Ferlan wrote:
>https://bugzilla.redhat.com/show_bug.cgi?id=1346566
>
>If libvirt_parthelper is erroneously told to append the partition
>separator 'p' onto the generated output for a disk pool using device
>mapper that has 'user_friendly_names' set to true, then the error
>recovery path will fail to find volume resulting in the pool being
>in an unusable state.
>
>So, augment the documentation to provide the better hint that the
>part_separator='yes' should be set when user_friendly_names are not
>being used. Additionally, once we're in the error path where the
>returned name doesn't match the expected partition name try to see
>if the reason is because the 'p' was erroneosly added. If so alter
>the about to be removed vol->target.path so that the DiskDeleteVol
>code can find the partition that was created and remove it.
>
>Signed-off-by: John Ferlan <jferlan at redhat.com>
>---
> docs/formatstorage.html.in         |  5 ++++-
> src/storage/storage_backend_disk.c | 23 +++++++++++++++++++++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
>diff --git a/docs/formatstorage.html.in b/docs/formatstorage.html.in
>index ed1f0d1..7690114 100644
>--- a/docs/formatstorage.html.in
>+++ b/docs/formatstorage.html.in
>@@ -138,7 +138,10 @@
>         causes libvirt to attempt to generate and find target volume path's
>         using a "p" separator. The default algorithm used by device mapper
>         is to add the "p" separator only when the source device path ends
>-        with a number.
>+        with a number; however, it's possible to configure the devmapper
>+        device to not use 'user_friendly_names' thus creating partitions
>+        with the "p" separator even when the device source path does not
>+        end with a number.
>         <span class="since">Since 1.3.1</span></p></dd>
>       <dt><code>dir</code></dt>
>       <dd>Provides the source for pools backed by directories (pool
>diff --git a/src/storage/storage_backend_disk.c b/src/storage/storage_backend_disk.c
>index 666ad03..07a04f1 100644
>--- a/src/storage/storage_backend_disk.c
>+++ b/src/storage/storage_backend_disk.c
>@@ -95,6 +95,29 @@ virStorageBackendDiskMakeDataVol(virStoragePoolObjPtr pool,
>         virReportError(VIR_ERR_INVALID_ARG,
>                        _("invalid partition name '%s', expected '%s'"),
>                        vol->name, partname);
>+
>+        /* Let's see if we by chance parthelper created a name that won't be

s/we //

ACK with that.  Safe for freeze, but feel free to wait for release if
there's no rush ;)

>+         * found later when we try to delete. We tell parthelper to add a 'p'
>+         * to the output via the part_separator flag, but if devmapper has
>+         * user_friendly_names set, the creation won't happen that way, thus
>+         * our deletion will fail because the name we generated is wrong.
>+         * Check for our conditions and see if the generated name is the
>+         * same as StablePath returns and has the 'p' in it */
>+        if (pool->def->source.devices[0].part_separator ==
>+            VIR_TRISTATE_BOOL_YES &&
>+            !virIsDevMapperDevice(vol->target.path) &&
>+            STREQ(groups[0], vol->target.path) &&
>+            (tmp = strrchr(groups[0], 'p'))) {
>+
>+            /* If we remove the 'p' from groups[0] and the resulting
>+             * device is a devmapper device, then we know parthelper
>+             * was told to create the wrong name based on the results.
>+             * So just remove the 'p' from the vol->target.path too. */
>+            memmove(tmp, tmp + 1, strlen(tmp));
>+            if (virIsDevMapperDevice(groups[0]) &&
>+                (tmp = strrchr(vol->target.path, 'p')))
>+                memmove(tmp, tmp + 1, strlen(tmp));
>+        }
>         return -1;
>     }
>
>--
>2.7.4
>
>--
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