[CRIU] [PATCH] page-xfer: Fixup page server protocol for lazy pages

[Mike Rapoport]

On Wed, Jun 21, 2017 at 5:10 PM, Pavel Emelyanov <xemul at virtuozzo.com> wrote:
> Introduce the PS_IOV_ADD_F command that is to add pages with
> flags. We already use the similar notation on page-xfer -- the
> single write callback with pagemap and flags. For page-server
> let's use the same. Legacy _HOLE and _PAGE handling is kept.
>
> Changed commands numbers are OK, as the commands in question
> are still in criu-dev branch.
>
> Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
> ---
>  criu/page-xfer.c | 49 +++++++++++++++++++++++++------------------------
>  1 file changed, 25 insertions(+), 24 deletions(-)
>
> diff --git a/criu/page-xfer.c b/criu/page-xfer.c
> index 49693bb..125001a 100644
> --- a/criu/page-xfer.c
> +++ b/criu/page-xfer.c
> @@ -42,9 +42,8 @@ static void psi2iovec(struct page_server_iov *ps, struct iovec *iov)
>  #define PS_IOV_OPEN    3
>  #define PS_IOV_OPEN2   4
>  #define PS_IOV_PARENT  5
> -#define PS_IOV_ZERO    6
> -#define PS_IOV_LAZY    7
> -#define PS_IOV_GET     8
> +#define PS_IOV_ADD_F   6
> +#define PS_IOV_GET     7
>
>  #define PS_IOV_FLUSH           0x1023
>  #define PS_IOV_FLUSH_N_CLOSE   0x1024
> @@ -118,18 +117,7 @@ static int write_pages_to_server(struct page_xfer *xfer,
>
>  static int write_pagemap_to_server(struct page_xfer *xfer, struct iovec *iov, u32 flags)
>  {
> -       u32 cmd = 0;
> -
> -       if (flags & PE_PRESENT)
> -               cmd = encode_ps_cmd(PS_IOV_ADD, flags);
> -       else if (flags & PE_PARENT)
> -               cmd = PS_IOV_HOLE;
> -       else if (flags & PE_LAZY)
> -               cmd = PS_IOV_LAZY;
> -       else
> -               BUG();
> -
> -       return send_psi(xfer->sk, cmd,
> +       return send_psi(xfer->sk, encode_ps_cmd(PS_IOV_ADD_F, flags),
>                         iov->iov_len / PAGE_SIZE, encode_pointer(iov->iov_base),
>                         xfer->dst_id);
>  }
> @@ -680,12 +668,13 @@ static int page_server_get_pages(int sk, struct page_server_iov *pi)
>         if (pi->nr_pages == 0) {
>                 /* no iovs found means we've hit a zero page */
>                 pr_debug("no iovs found, zero pages\n");
> -               return send_psi(sk, PS_IOV_ZERO, 0, 0, 0);
> +               return send_psi(sk, encode_ps_cmd(PS_IOV_ADD_F, 0), 0, 0, 0);
>         }
>
>         len = pi->nr_pages * PAGE_SIZE;
>
> -       if (send_psi(sk, PS_IOV_ADD, pi->nr_pages, pi->vaddr, pi->dst_id))
> +       if (send_psi(sk, encode_ps_cmd(PS_IOV_ADD_F, PE_PRESENT),
> +                               pi->nr_pages, pi->vaddr, pi->dst_id))
>                 return -1;
>
>         ret = splice(pipe_read_dest.p[0], NULL, sk, NULL, len, SPLICE_F_MOVE);
> @@ -751,15 +740,22 @@ static int page_server_serve(int sk)
>                 case PS_IOV_PARENT:
>                         ret = page_server_check_parent(sk, &pi);
>                         break;
> +               case PS_IOV_ADD_F:
>                 case PS_IOV_ADD:
> -                       ret = page_server_add(sk, &pi, PE_PRESENT | decode_ps_flags(pi.cmd));
> -                       break;
>                 case PS_IOV_HOLE:
> -                       ret = page_server_add(sk, &pi, PE_PARENT);
> -                       break;
> -               case PS_IOV_LAZY:
> -                       ret = page_server_add(sk, &pi, PE_LAZY);
> +               {
> +                       u32 flags;
> +
> +                       if (likely(cmd == PS_IOV_ADD_F))
> +                               flags = decode_ps_flags(pi.cmd);
> +                       else if (cmd == PS_IOV_ADD)
> +                               flags = PE_PRESENT;
> +                       else    /* PS_IOV_HOLE */
> +                               flags = PE_PARENT;

Maybe a helper function here ?

> +                       ret = page_server_add(sk, &pi, flags);
>                         break;
> +               }
>                 case PS_IOV_FLUSH:
>                 case PS_IOV_FLUSH_N_CLOSE:
>                 {
> @@ -1162,7 +1158,12 @@ int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>                 return -1;
>         }
>
> -       if (pi.cmd == PS_IOV_ZERO)
> +       if (decode_ps_cmd(pi.cmd) != PS_IOV_ADD_F) {
> +               pr_err("Proto error\n");
> +               return -1;
> +       }
> +
> +       if (!(decode_ps_flags(pi.cmd) & PE_PRESENT))
>                 pr_warn("Unexpected ZERO page received for %d.%lx\n",
>                                 (int)pi.dst_id, (unsigned long)pi.vaddr);
>
> --
> 2.1.4
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-- 
Sincerely yours,
Mike.