[CRIU] [RFC PATCH 10/16] criu: lazy_pages: make buffer for copying pages per-process

[Pavel Emelyanov]

Some comment here would be nice too.

On 09/27/2016 04:42 PM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/uffd.c | 52 +++++++++++++++++++++++++---------------------------
>  1 file changed, 25 insertions(+), 27 deletions(-)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 5910226..b949d1c 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -62,6 +62,8 @@ struct lazy_pages_info {
>  	unsigned long copied_pages;
>  
>  	struct hlist_node hash;
> +
> +	void *buf;
>  };
>  
>  #define LPI_HASH_SIZE	16
> @@ -375,7 +377,7 @@ 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;
> +	int nr_pages = 0, max_iov_len = 0;
>  
>  	pr->reset(pr);
>  
> @@ -395,9 +397,15 @@ static int collect_lazy_iovecs(struct lazy_pages_info *lpi)
>  		list_add_tail(&lazy_iov->l, &lpi->iovs);
>  		nr_pages += pe->nr_pages;
>  
> +		if (lazy_iov->iov.iov_len > max_iov_len)
> +			max_iov_len = lazy_iov->iov.iov_len;
> +
>  		pr_debug("adding IOV: %p:%lx (%d)\n", lazy_iov->iov.iov_base, lazy_iov->iov.iov_len, pe->nr_pages);
>  	}
>  
> +	if (posix_memalign(&lpi->buf, PAGE_SIZE, max_iov_len))
> +		goto free_iovs;
> +
>  	return nr_pages;
>  
>  free_iovs:
> @@ -468,7 +476,7 @@ out:
>  	return NULL;
>  }
>  
> -static int get_page(struct lazy_pages_info *lpi, unsigned long addr, void *dest)
> +static int get_page(struct lazy_pages_info *lpi, unsigned long addr)
>  {
>  	int ret;
>  	unsigned char buf[PAGE_SIZE];
> @@ -488,26 +496,25 @@ static int get_page(struct lazy_pages_info *lpi, unsigned long addr, void *dest)
>  	if (ret <= 0)
>  		return ret;
>  
> -	memcpy(dest, buf, PAGE_SIZE);
> +	memcpy(lpi->buf, buf, PAGE_SIZE);
>  
>  	return 1;
>  }
>  
> -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, lpi->buf);
>  	else
> -		rc = get_page(lpi, address, dest);
> +		rc = get_page(lpi, address);
>  	if (rc <= 0)
>  		return rc;
>  
>  	uffdio_copy.dst = address;
> -	uffdio_copy.src = (unsigned long) dest;
> +	uffdio_copy.src = (unsigned long)lpi->buf;
>  	uffdio_copy.len = page_size();
>  	uffdio_copy.mode = 0;
>  	uffdio_copy.copy = 0;
> @@ -555,19 +562,18 @@ 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);
>  
>  	return rc;
>  }
>  
> -static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
> +static int handle_remaining_pages(struct lazy_pages_info *lpi)
>  {
>  	struct lazy_iovec *lazy_iov;
>  	int nr_pages, i, err;
> @@ -582,7 +588,7 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
>  		for (i = 0; i < nr_pages; i++) {
>  			addr = base + i * PAGE_SIZE;
>  
> -			err = uffd_handle_page(lpi, addr, dest);
> +			err = uffd_handle_page(lpi, addr);
>  			if (err < 0) {
>  				pr_err("Error during UFFD copy\n");
>  				return -1;
> @@ -593,12 +599,11 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
>  	return 0;
>  }
>  
> -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;
>  
> -	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;
> @@ -611,7 +616,7 @@ static int handle_regular_pages(struct lazy_pages_info *lpi, void *dest,
>  	return 0;
>  }
>  
> -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;
> @@ -641,7 +646,7 @@ static int handle_user_fault(struct lazy_pages_info *lpi, void *dest)
>  		return -1;
>  	}
>  
> -	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;
> @@ -672,14 +677,8 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  	int nr_fds = task_entries->nr_tasks;
>  	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 = malloc(ps);
> -
>  	while (1) {
>  		/*
>  		 * Setting the timeout to 5 seconds. If after this time
> @@ -701,7 +700,7 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  			int err;
>  			lpi = uffd_to_lpi(events[i].data.fd);
>  			BUG_ON(!lpi);
> -			err = handle_user_fault(lpi, dest);
> +			err = handle_user_fault(lpi);
>  			if (err < 0)
>  				goto out;
>  		}
> @@ -709,7 +708,7 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  	pr_debug("Handle remaining pages\n");
>  	for (i = 0; i < LPI_HASH_SIZE; i++) {
>  		hlist_for_each_entry(lpi, &lpi_hash[i], hash) {
> -			ret = handle_remaining_pages(lpi, dest);
> +			ret = handle_remaining_pages(lpi);
>  			if (ret < 0) {
>  				pr_err("Error during remaining page copy\n");
>  				ret = 1;
> @@ -723,7 +722,6 @@ static int handle_requests(int epollfd, struct epoll_event *events)
>  			ret += lazy_pages_summary(lpi);
>  
>  out:
> -	free(dest);
>  	return ret;
>  
>  }
>