[CRIU] [RFC PATCH] Try to include userfaultfd with criu

[Adrian Reber]

On Mon, Oct 26, 2015 at 07:13:06PM +0300, Pavel Emelyanov wrote:
> On 10/26/2015 03:41 PM, Adrian Reber wrote:
> > Pavel, thanks for the comments on the userfaultfd integration. I am
> > trying to integrate all your suggestions. I have question about
> > restoring pages... Or rather about not restoring pages.
> > 
> > My current approach is, if the parameter --lazy-pages is specified, to
> > skip pages with MAP_ANONYMOUS. I thought about skipping the pages in
> > restore_priv_vma_content(). 
> 
> Correct.
> 
> > If I skip pages I need to seek with a
> > different value then '0' in read_pagemap_page() to read from the right
> > position from the pages-x.img file.
> 
> Yes, there's skip_pagemap_pages() call for that :)

So what do you say to a patch like this:

diff --git a/include/page-read.h b/include/page-read.h
index 9e3013a..e973426 100644
--- a/include/page-read.h
+++ b/include/page-read.h
@@ -51,6 +51,7 @@ struct page_read {
        /* stop working on current pagemap */
        void (*put_pagemap)(struct page_read *);
        void (*close)(struct page_read *);
+       void (*skip_pages)(struct page_read *, unsigned long len);
 
        /* Private data of reader */
        struct cr_img *pmi;
diff --git a/page-read.c b/page-read.c
index 832c057..6c0bb95 100644
--- a/page-read.c
+++ b/page-read.c
@@ -279,6 +279,7 @@ int open_page_read_at(int dfd, int pid, struct page_read *pr, int pr_flags)
        pr->put_pagemap = put_pagemap;
        pr->read_page = read_pagemap_page;
        pr->close = close_page_read;
+       pr->skip_pages = skip_pagemap_pages;
        pr->id = ids++;
 
        pr_debug("Opened page read %u (parent %u)\n",
@@ -301,6 +302,7 @@ open_old:
        pr->read_page = read_page;
        pr->pi = NULL;
        pr->close = close_page_read;
+       pr->skip_pages = NULL;
 
        return 1;
 }

This way I can use skip pages in cr-restore.c and I am only reading
the pages I cannot restore via uffd. I could submit this as proper
patch independent of the uffd functionality.

		Adrian