[CRIU] [PATCH 08/10] uffd: Don't carry void *page through the callstack

[Mike Rapoport]

On Sat, Nov 12, 2016 at 08:25:44AM +0300, Pavel Emelyanov wrote:
> Since all #PFs are serialized with a mutex it seems reasonable
> to have a global page_szie() buffer nearby.

I don't remember any mutex for #PF syncronization. They might be serialized
because we do things one by one at the moment, but in the future we might
want to have a buffer per process to hold the data.
 
> Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
> ---
>  criu/uffd.c | 39 ++++++++++++++++++---------------------
>  1 file changed, 18 insertions(+), 21 deletions(-)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 96b5ec0..25e13ab 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -46,6 +46,7 @@
>  #define LAZY_PAGES_SOCK_NAME	"lazy-pages.socket"
> 
>  static mutex_t *lazy_sock_mutex;
> +static void *aux_page;
> 
>  struct lazy_pages_info {
>  	int pid;
> @@ -375,21 +376,20 @@ struct uffd_pages_struct {
>  	int flags;
>  };
> 
> -static int uffd_copy_page(struct lazy_pages_info *lpi, __u64 address,
> -			  void *dest)
> +static int uffd_copy_page(struct lazy_pages_info *lpi, __u64 address)
>  {
>  	struct uffdio_copy uffdio_copy;
>  	int rc;
> 
>  	if (opts.use_page_server)
> -		rc = get_remote_pages(lpi->pid, address, 1, dest);
> +		rc = get_remote_pages(lpi->pid, address, 1, aux_page);
>  	else
> -		rc = get_page(lpi, address, dest);
> +		rc = get_page(lpi, address, aux_page);
>  	if (rc <= 0)
>  		return rc;
> 
>  	uffdio_copy.dst = address;
> -	uffdio_copy.src = (unsigned long) dest;
> +	uffdio_copy.src = (unsigned long) aux_page;
>  	uffdio_copy.len = page_size();
>  	uffdio_copy.mode = 0;
>  	uffdio_copy.copy = 0;
> @@ -437,12 +437,11 @@ static int uffd_zero_page(struct lazy_pages_info *lpi, __u64 address)
>  	return ps;
>  }
> 
> -static int uffd_handle_page(struct lazy_pages_info *lpi, __u64 address,
> -			    void *dest)
> +static int uffd_handle_page(struct lazy_pages_info *lpi, __u64 address)
>  {
>  	int rc;
> 
> -	rc = uffd_copy_page(lpi, address, dest);
> +	rc = uffd_copy_page(lpi, address);
>  	if (rc == 0)
>  		rc = uffd_zero_page(lpi, address);
> 
> @@ -518,7 +517,7 @@ static int collect_uffd_pages(struct page_read *pr, struct lazy_pages_info *lpi)
>  	return 0;
>  }
> 
> -static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
> +static int handle_remaining_pages(struct lazy_pages_info *lpi)
>  {
>  	struct uffd_pages_struct *uffd_pages;
>  	int rc;
> @@ -529,7 +528,7 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
>  		if (uffd_pages->flags & UFFD_FLAG_SENT)
>  			continue;
> 
> -		rc = uffd_handle_page(lpi, uffd_pages->addr, dest);
> +		rc = uffd_handle_page(lpi, uffd_pages->addr);
>  		if (rc < 0) {
>  			pr_err("Error during UFFD copy\n");
>  			return -1;
> @@ -542,13 +541,12 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
>  }
> 
> 
> -static int handle_regular_pages(struct lazy_pages_info *lpi, void *dest,
> -				__u64 address)
> +static int handle_regular_pages(struct lazy_pages_info *lpi, __u64 address)
>  {
>  	int rc;
>  	struct uffd_pages_struct *uffd_pages;
> 
> -	rc = uffd_handle_page(lpi, address, dest);
> +	rc = uffd_handle_page(lpi, address);
>  	if (rc < 0) {
>  		pr_err("Error during UFFD copy\n");
>  		return -1;
> @@ -647,7 +645,7 @@ out:
>  	return ret;
>  }
> 
> -static int handle_user_fault(struct lazy_pages_info *lpi, void *dest)
> +static int handle_user_fault(struct lazy_pages_info *lpi)
>  {
>  	struct uffd_msg msg;
>  	__u64 flags;
> @@ -686,7 +684,7 @@ static int handle_user_fault(struct lazy_pages_info *lpi, void *dest)
>  	flags = msg.arg.pagefault.flags;
>  	pr_debug("msg.arg.pagefault.flags 0x%llx\n", flags);
> 
> -	ret = handle_regular_pages(lpi, dest, address);
> +	ret = handle_regular_pages(lpi, address);
>  	if (ret < 0) {
>  		pr_err("Error during regular page copy\n");
>  		return -1;
> @@ -718,13 +716,12 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  	struct lazy_pages_info *lpi;
>  	int ret = -1;
>  	unsigned long ps;
> -	void *dest;
>  	int i;
> 
>  	/* All operations will be done on page size */
>  	ps = page_size();
> -	dest = xmalloc(ps);
> -	if (!dest)
> +	aux_page = xmalloc(ps);
> +	if (!aux_page)
>  		return ret;
> 
>  	while (1) {
> @@ -748,14 +745,14 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  			int err;
> 
>  			lpi = (struct lazy_pages_info *)events[i].data.ptr;
> -			err = handle_user_fault(lpi, dest);
> +			err = handle_user_fault(lpi);
>  			if (err < 0)
>  				goto out;
>  		}
>  	}
>  	pr_debug("Handle remaining pages\n");
>  	list_for_each_entry(lpi, &lpis, l) {
> -		ret = handle_remaining_pages(lpi, dest);
> +		ret = handle_remaining_pages(lpi);
>  		if (ret < 0) {
>  			pr_err("Error during remaining page copy\n");
>  			ret = 1;
> @@ -767,7 +764,7 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  		ret += lazy_pages_summary(lpi);
> 
>  out:
> -	free(dest);
> +	free(aux_page);
>  	return ret;
> 
>  }
> -- 
> 2.5.0
> _______________________________________________
> CRIU mailing list
> CRIU at openvz.org
> https://lists.openvz.org/mailman/listinfo/criu
>