[CRIU] [RFC PATCH 03/16] criu: lazy-pages: introduce collect_lazy_iovecs

[Pavel Emelyanov]

On 09/27/2016 04:42 PM, Mike Rapoport wrote:
> Instead of tracking memory handled by userfaultfd on the page basis we can
> use IOVs for continious chunks. Start conversion by introducing
> collect_lazy_iovecs function.
> 
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/uffd.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 81dc7ae..063ce4f 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -45,11 +45,17 @@
>  
>  static mutex_t *lazy_sock_mutex;
>  
> +struct lazy_iovec {
> +	struct iovec iov;
> +	struct list_head l;
> +};
> +
>  struct lazy_pages_info {
>  	int pid;
>  	int uffd;
>  
>  	struct list_head pages;
> +	struct list_head iovs;
>  
>  	struct page_read pr;
>  
> @@ -74,6 +80,7 @@ static struct lazy_pages_info *lpi_init(void)
>  
>  	memset(lpi, 0, sizeof(*lpi));
>  	INIT_LIST_HEAD(&lpi->pages);
> +	INIT_LIST_HEAD(&lpi->iovs);
>  	INIT_HLIST_NODE(&lpi->hash);
>  
>  	return lpi;
> @@ -81,8 +88,12 @@ static struct lazy_pages_info *lpi_init(void)
>  
>  static void lpi_fini(struct lazy_pages_info *lpi)
>  {
> +	struct lazy_iovec *p, *n;
> +
>  	if (!lpi)
>  		return;
> +	list_for_each_entry_safe(p, n, &lpi->iovs, l)
> +		xfree(p);
>  	if (lpi->uffd > 0)
>  		close(lpi->uffd);
>  	if (lpi->pr.close)
> @@ -314,6 +325,42 @@ out:
>  
>  static int find_vmas(struct lazy_pages_info *lpi);
>  
> +static int collect_lazy_iovecs(struct lazy_pages_info *lpi)
> +{
> +	struct page_read *pr = &lpi->pr;
> +	struct lazy_iovec *lazy_iov, *n;
> +	int nr_pages = 0;
> +
> +	pr->reset(pr);
> +
> +	while (pr->advance(pr)) {

This place looks like it wanted to do pr->get_pagemap(), but for
some reason it doesn't :) Why?

> +		PagemapEntry *pe = pr->pe;
> +
> +		if (!pagemap_lazy(pe))
> +			continue;
> +
> +		lazy_iov = xzalloc(sizeof(*lazy_iov));
> +		if (!lazy_iov) {
> +			pr_err("Out of memory\n");
> +			goto free_iovs;
> +		}
> +
> +		pagemap2iovec(pe, &lazy_iov->iov);
> +		list_add_tail(&lazy_iov->l, &lpi->iovs);
> +		nr_pages += pe->nr_pages;
> +
> +		pr_debug("adding IOV: %p:%lx (%d)\n", lazy_iov->iov.iov_base, lazy_iov->iov.iov_len, pe->nr_pages);
> +	}
> +
> +	return nr_pages;
> +
> +free_iovs:
> +	list_for_each_entry_safe(lazy_iov, n, &lpi->iovs, l)
> +		xfree(lazy_iov);
> +
> +	return -1;
> +}
> +
>  static struct lazy_pages_info *ud_open(int client)
>  {
>  	struct lazy_pages_info *lpi;
> @@ -353,6 +400,12 @@ static struct lazy_pages_info *ud_open(int client)
>  
>  	hlist_add_head(&lpi->hash, &lpi_hash[lpi->uffd % LPI_HASH_SIZE]);
>  
> +	ret = collect_lazy_iovecs(lpi);
> +	if (ret != lpi->total_pages) {
> +		pr_err("collect_lazy_iovecs=%d\n", ret);
> +		goto out;
> +	}
> +
>  	return lpi;
>  
>  out:
>