[libvirt] [PATCH 2/4] qemu: block: use the delete flag to delete snapshot images if requested

[Pavel Mores]

On Wed, Nov 20, 2019 at 10:55:25AM +0100, Pavel Mores wrote:
> When blockcommit finishes successfully, one of the
> qemuBlockJobProcessEventCompletedCommit() and
> qemuBlockJobProcessEventCompletedActiveCommit() event handlers is called.
> This is where the delete flag (stored in qemuBlockJobCommitData since the
> previous commit) can actually be used to delete the committed snapshot
> images if requested.
> 
> Signed-off-by: Pavel Mores <pmores at redhat.com>
> ---
>  src/qemu/qemu_blockjob.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/src/qemu/qemu_blockjob.c b/src/qemu/qemu_blockjob.c
> index 7d94a6ce38..dae1fa44c8 100644
> --- a/src/qemu/qemu_blockjob.c
> +++ b/src/qemu/qemu_blockjob.c
> @@ -965,6 +965,31 @@ qemuBlockJobProcessEventCompletedPull(virQEMUDriverPtr driver,
>  }
>  
>  
> +/**
> + * Helper for qemuBlockJobProcessEventCompletedCommit() and
> + * qemuBlockJobProcessEventCompletedActiveCommit().  Relies on adjustments
> + * these functions perform on the 'backingStore' chain to function correctly.
> + *
> + * TODO look into removing backing store for non-local snapshots too
> + */
> +static void
> +qemuBlockJobUnlinkCommittedStorage(virStorageSourcePtr top)
> +{
> +    virStorageSourcePtr p = top;
> +    const size_t errmsg_len = 128;
> +    char errmsg[errmsg_len];
> +
> +    for (; p != NULL; p = p->backingStore) {
> +        if (virStorageSourceIsLocalStorage(p))
> +            if (unlink(p->path) < 0) {
> +                char *dummy = strerror_r(errno, errmsg, errmsg_len);
> +                (void)dummy;

Sorry, just realised that a non-standard version of strerror_r() is used here
where the return value is actually useful.  I'll fix this is in v2.

> +                VIR_WARN("Unable to remove snapshot image file %s (%s)",
> +                         p->path, errmsg);
> +            }
> +    }
> +}
> +
>  /**
>   * qemuBlockJobProcessEventCompletedCommit:
>   * @driver: qemu driver object
> @@ -1031,6 +1056,9 @@ qemuBlockJobProcessEventCompletedCommit(virQEMUDriverPtr driver,
>      job->data.commit.topparent->backingStore = job->data.commit.base;
>  
>      qemuBlockJobEventProcessConcludedRemoveChain(driver, vm, asyncJob, job->data.commit.top);
> +
> +    if (job->data.commit.deleteCommittedImages)
> +        qemuBlockJobUnlinkCommittedStorage(job->data.commit.top);
>      virObjectUnref(job->data.commit.top);
>      job->data.commit.top = NULL;
>  
> @@ -1121,6 +1149,9 @@ qemuBlockJobProcessEventCompletedActiveCommit(virQEMUDriverPtr driver,
>      job->disk->src->readonly = job->data.commit.top->readonly;
>  
>      qemuBlockJobEventProcessConcludedRemoveChain(driver, vm, asyncJob, job->data.commit.top);
> +
> +    if (job->data.commit.deleteCommittedImages)
> +        qemuBlockJobUnlinkCommittedStorage(job->data.commit.top);
>      virObjectUnref(job->data.commit.top);
>      job->data.commit.top = NULL;
>      /* the mirror element does not serve functional purpose for the commit job */
> -- 
> 2.21.0
>