[Virtio-fs] [PATCH] virtiofsd: do fallocate for setupmapping requests with write flag

[Tao Peng]

On Tue, May 7, 2019 at 1:58 PM Liu Bo <bo.liu at linux.alibaba.com> wrote:
>
> We'll have to make sure filesystem has allocated space for the dax
> mapping, otherwise, guest writes from virtiofs may hang since write
> page fault is not able to be resolved if host fs is full
> (->page_mkwrite() return -ENOSPC).
>
> Signed-off-by: Liu Bo <bo.liu at linux.alibaba.com>
Reviewed-by: Peng Tao <bergwolf at hyper.sh>

> ---
>  contrib/virtiofsd/passthrough_ll.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
> index f14f471..1ddb68f 100644
> --- a/contrib/virtiofsd/passthrough_ll.c
> +++ b/contrib/virtiofsd/passthrough_ll.c
> @@ -1897,12 +1897,28 @@ static void lo_setupmapping(fuse_req_t req, fuse_ino_t ino, uint64_t foffset,
>
>         }
>
> +        if (flags & O_WRONLY) {
> +                /* this may allocate more space than we need. */
> +                ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, foffset, len);
> +                if (ret < 0) {
> +                        ret = errno;
> +                        fprintf(stderr, "%s: fallocate fail (ino=%" PRId64 "fd=%d foffset=0x%" PRIx64 ")\n",
> +                                __func__, ino, fi ? (int)fi->fh : lo_fd(req, ino), foffset);
> +                        goto err;
> +                }
> +
> +                if (lo_debug(req))
> +                        fprintf(stderr, "fallocate (foffset=%" PRIx64 "moffset=%" PRIx64 ")\n",
> +                                foffset, moffset);
> +        }
> +
>          if (fuse_virtio_map(req, &msg, fd)) {
>                  fprintf(stderr, "%s: map over virtio failed (ino=%" PRId64 "fd=%d moffset=0x%" PRIx64 ")\n",
>                          __func__, ino, fi ? (int)fi->fh : lo_fd(req, ino), moffset);
>                  ret = EINVAL;
>          }
>
> +err:
>         if (!fi)
>                 close(fd);
>         fuse_reply_err(req, ret);
> --
> 1.8.3.1
>
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-- 
bergwolf at hyper.sh