[CRIU] [PATCH 4/7] page-read: Introduce PR_ASAP flag for read_pages

[Mike Rapoport]

On Wed, Nov 16, 2016 at 11:39 AM, Pavel Emelyanov <xemul at virtuozzo.com> wrote:
> This flag means, that the PR_ASYNC is valid, but the IO
> should be started ASAP. This is how remote reader works,
> so this flag is mostly for the local reader. It will let
> us unify page-fault handlers for local and remote cases.

A nitpeek below, otherwise

> Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
> ---

Acked-by: Mike Rapoport <rppt at linux.vnet.ibm.com>

>  criu/include/pagemap.h | 1 +
>  criu/pagemap.c         | 9 ++++++++-
>  criu/uffd.c            | 4 ++--
>  3 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/criu/include/pagemap.h b/criu/include/pagemap.h
> index 98ad7ae..fbe8ca0 100644
> --- a/criu/include/pagemap.h
> +++ b/criu/include/pagemap.h
> @@ -87,6 +87,7 @@ struct page_read {
>
>  /* flags for ->read_pages */
>  #define PR_ASYNC       0x1 /* may exit w/o data in the buffer */
> +#define PR_ASAP                0x2 /* PR_ASYNC, but start the IO right now */

Why so many whitespace?

>  /* flags for open_page_read */
>  #define PR_SHMEM       0x1
> diff --git a/criu/pagemap.c b/criu/pagemap.c
> index 86791d7..a9c37d7 100644
> --- a/criu/pagemap.c
> +++ b/criu/pagemap.c
> @@ -384,7 +384,13 @@ static int maybe_read_page_local(struct page_read *pr, unsigned long vaddr,
>         int ret;
>         unsigned long len = nr * PAGE_SIZE;
>
> -       if (flags & PR_ASYNC)
> +       /*
> +        * There's no API in the kernel to start asynchronous
> +        * cached read (or write), so in case someone is asking
> +        * for us for urgent async read, just do the regular
> +        * cached read.
> +        */
> +       if ((flags & (PR_ASYNC|PR_ASAP)) == PR_ASYNC)
>                 ret = enqueue_async_page(pr, vaddr, len, buf);
>         else
>                 ret = read_local_page(pr, vaddr, len, buf);
> @@ -399,6 +405,7 @@ static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
>  {
>         int ret, pid;
>
> +       /* We always do PR_ASAP mode here (FIXME?) */
>         ret = request_remote_pages(pr->pid, vaddr, nr);
>         if ((ret < 0) || (flags & PR_ASYNC))
>                 return ret;
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 7efccf5..46ac9f2 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -686,7 +686,7 @@ static int page_fault_common(struct lazy_pages_info *lpi, __u64 address, int nr,
>
>  static int page_fault_local(struct lazy_pages_info *lpi, __u64 address, int nr)
>  {
> -       if (page_fault_common(lpi, address, nr, 0))
> +       if (page_fault_common(lpi, address, nr, PR_ASYNC | PR_ASAP))
>                 return -1;
>
>         if (uffd_copy(lpi, address, nr))
> @@ -700,7 +700,7 @@ static int page_fault_local(struct lazy_pages_info *lpi, __u64 address, int nr)
>
>  static int page_fault_remote(struct lazy_pages_info *lpi, __u64 address, int nr)
>  {
> -       return page_fault_common(lpi, address, nr, PR_ASYNC);
> +       return page_fault_common(lpi, address, nr, PR_ASYNC | PR_ASAP);
>  }
>
>  static int (*pf_handler)(struct lazy_pages_info *lpi, __u64 address, int nr);
> --
> 2.5.0
>



-- 
Sincerely yours,
Mike.