Re: [Qemu-devel] [PATCH v6 06/24] memfd: add fallback for memfd

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 29, 2015 at 06:34:36PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Add an open/unlink/mmap fallback for system that do not support memfd.
> This patch may require additional SELinux policies to work for enforced
> systems, but should gracefully fail nonetheless.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

I'd rather just fail migration.

> ---
>  util/memfd.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/util/memfd.c b/util/memfd.c
> index 3168902..970b5b0 100644
> --- a/util/memfd.c
> +++ b/util/memfd.c
> @@ -84,8 +84,26 @@ void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
>              return NULL;
>          }
>      } else {
> -        perror("memfd");
> -        return NULL;
> +        const char *tmpdir = getenv("TMPDIR");
> +        gchar *fname;
> +
> +        tmpdir = tmpdir ? tmpdir : "/tmp";
> +
> +        fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
> +        mfd = mkstemp(fname);
> +        unlink(fname);
> +        g_free(fname);
> +
> +        if (mfd == -1) {
> +            perror("mkstemp");
> +            return NULL;
> +        }
> +
> +        if (ftruncate(mfd, size) == -1) {
> +            perror("ftruncate");
> +            close(mfd);
> +            return NULL;
> +        }
>      }
>  
>      ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
> -- 
> 2.4.3