Re: [QEMU HCI-8.0 PATCH v2 3/5] vhost-blk: add read-only flag

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

> and set RO respectively. Also compare BLKROGET with the selected

Please have commit message start their own sentences.

> mode and reject r/w if needed.
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-143437
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
>
> diff --git a/hw/block/vhost-blk.c b/hw/block/vhost-blk.c
> index 24f4fbe2b68..04a7013e521 100644
> --- a/hw/block/vhost-blk.c
> +++ b/hw/block/vhost-blk.c
> @@ -24,6 +24,7 @@
>  #include "system/system.h"
>  #include "linux-headers/linux/vhost.h"
>  #include <sys/ioctl.h>
> +#include <linux/fs.h>

Header belongs to patch 2.

>  #include "system/runstate.h"
>  
>  static int vhost_blk_start(VirtIODevice *vdev)
> @@ -232,8 +233,9 @@ static bool vhost_blk_open_backend(VHostBlk *s, Error **errp)
>      BlockConf *conf = &s->conf.conf;
>      struct stat st;
>      bool changed;
> +    int open_flags = s->conf.readonly ? O_RDONLY : O_RDWR;
>  
> -    s->backend_fd = qemu_open(s->conf.devpath, O_RDWR, errp);
> +    s->backend_fd = qemu_open(s->conf.devpath, open_flags, errp);
>      if (s->backend_fd < 0) {
>          error_prepend(errp, "vhost-blk: unable to open backend: ");
>          return false;
> @@ -251,6 +253,23 @@ static bool vhost_blk_open_backend(VHostBlk *s, Error **errp)
>          goto fail;
>      }
>  
> +    if (!s->conf.readonly) {
> +        int readonly;
> +
> +        if (ioctl(s->backend_fd, BLKROGET, &readonly) < 0) {
> +            error_setg_errno(errp, errno,
> +                             "vhost-blk: unable to get read-only status of "
> +                             "'%s'", s->conf.devpath);
> +            goto fail;
> +        }
> +
> +        if (readonly) {
> +            error_setg_errno(errp, EROFS, "vhost-blk: '%s' is not writable",
> +                             s->conf.devpath);
> +            goto fail;
> +        }
> +    }
> +
>      if (vhost_blk_update_size(s, &changed, errp) < 0) {
>          goto fail;
>      }
> @@ -406,6 +425,10 @@ static uint64_t vhost_blk_get_features(VirtIODevice *vdev,
>  
>      virtio_add_feature(&features, VIRTIO_F_VERSION_1);
>  
> +    if (s->conf.readonly) {
> +        virtio_add_feature(&features, VIRTIO_BLK_F_RO);
> +    }
> +
>      if (s->conf.num_queues > 1) {
>          virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
>      }
> @@ -453,6 +476,7 @@ static void vhost_blk_update_config(VirtIODevice *vdev, uint8_t *config)
>  
>  static const Property vhost_blk_properties[] = {
>      DEFINE_PROP_STRING("devpath", VHostBlk, conf.devpath),
> +    DEFINE_PROP_BOOL("read-only", VHostBlk, conf.readonly, false),

Not for this patch, but related: AFAIU currently "<readonly/>" in domain
XML is applied by libvirt to the block node.  Correct?  If so - we also
need to patch libvirt making sure it applies to the device.

Andrey

-- 
Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>