[CRIU] [PATCH RFC 2/8] criu: page_pipe_buf: add PPB_LAZY flag

[Pavel Emelyanov]

On 05/21/2016 01:49 PM, Mike Rapoport wrote:
> for buffers that contain potentially lazy pages

But... Why a buffer would contain lazy pages?

> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/include/page-pipe.h |  5 ++++-
>  criu/mem.c               |  6 +++++-
>  criu/page-pipe.c         | 30 ++++++++++++++++++------------
>  criu/shmem.c             |  2 +-
>  4 files changed, 28 insertions(+), 15 deletions(-)
> 
> diff --git a/criu/include/page-pipe.h b/criu/include/page-pipe.h
> index a2dc268..031f145 100644
> --- a/criu/include/page-pipe.h
> +++ b/criu/include/page-pipe.h
> @@ -74,6 +74,8 @@ struct page_pipe_buf {
>  	unsigned int pipe_size;	/* how many pages can be fit into pipe */
>  	unsigned int pages_in;	/* how many pages are there */
>  	unsigned int nr_segs;	/* how many iov-s are busy */
> +#define PPB_LAZY (1 << 0)
> +	unsigned int flags;
>  	struct iovec *iov;	/* vaddr:len map */
>  	struct list_head l;	/* links into page_pipe->bufs */
>  };
> @@ -98,7 +100,8 @@ struct page_pipe {
>  extern struct page_pipe *create_page_pipe(unsigned int nr,
>  					  struct iovec *, bool chunk_mode);
>  extern void destroy_page_pipe(struct page_pipe *p);
> -extern int page_pipe_add_page(struct page_pipe *p, unsigned long addr);
> +extern int page_pipe_add_page(struct page_pipe *p, unsigned long addr,
> +			      unsigned int flags);
>  extern int page_pipe_add_hole(struct page_pipe *p, unsigned long addr);
>  
>  extern void debug_show_page_pipe(struct page_pipe *pp);
> diff --git a/criu/mem.c b/criu/mem.c
> index becbd6d..0497975 100644
> --- a/criu/mem.c
> +++ b/criu/mem.c
> @@ -137,6 +137,7 @@ static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u
>  
>  	for (pfn = 0; pfn < nr_to_scan; pfn++) {
>  		unsigned long vaddr;
> +		unsigned int ppb_flags = 0;
>  		int ret;
>  
>  		if (!should_dump_page(vma->e, at[pfn]))
> @@ -144,6 +145,9 @@ static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u
>  
>  		vaddr = vma->e->start + *off + pfn * PAGE_SIZE;
>  
> +		if (vma_entry_can_be_lazy(vma->e))
> +			ppb_flags |= PPB_LAZY;
> +
>  		/*
>  		 * If we're doing incremental dump (parent images
>  		 * specified) and page is not soft-dirty -- we dump
> @@ -155,7 +159,7 @@ static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u
>  			ret = page_pipe_add_hole(pp, vaddr);
>  			pages[0]++;
>  		} else {
> -			ret = page_pipe_add_page(pp, vaddr);
> +			ret = page_pipe_add_page(pp, vaddr, ppb_flags);
>  			pages[1]++;
>  		}
>  
> diff --git a/criu/page-pipe.c b/criu/page-pipe.c
> index db58f6a..78f8271 100644
> --- a/criu/page-pipe.c
> +++ b/criu/page-pipe.c
> @@ -25,7 +25,7 @@ static inline void iov_init(struct iovec *iov, unsigned long addr)
>  	iov->iov_len = PAGE_SIZE;
>  }
>  
> -static int page_pipe_grow(struct page_pipe *pp)
> +static int page_pipe_grow(struct page_pipe *pp, unsigned int flags)
>  {
>  	struct page_pipe_buf *ppb;
>  
> @@ -57,6 +57,7 @@ static int page_pipe_grow(struct page_pipe *pp)
>  out:
>  	ppb->pages_in = 0;
>  	ppb->nr_segs = 0;
> +	ppb->flags = flags;
>  	ppb->iov = &pp->iovs[pp->free_iov];
>  
>  	return 0;
> @@ -84,7 +85,7 @@ struct page_pipe *create_page_pipe(unsigned int nr_segs,
>  
>  		pp->chunk_mode = chunk_mode;
>  
> -		if (page_pipe_grow(pp))
> +		if (page_pipe_grow(pp, 0))
>  			return NULL;
>  	}
>  
> @@ -120,13 +121,16 @@ void page_pipe_reinit(struct page_pipe *pp)
>  
>  	pp->free_hole = 0;
>  
> -	if (page_pipe_grow(pp))
> +	if (page_pipe_grow(pp, 0))
>  		BUG(); /* It can't fail, because ppb is in free_bufs */
>  }
>  
>  static inline int try_add_page_to(struct page_pipe *pp, struct page_pipe_buf *ppb,
> -		unsigned long addr)
> +		unsigned long addr, unsigned int flags)
>  {
> +	if (ppb->flags != flags)
> +		return 1;
> +
>  	if (ppb->pages_in == ppb->pipe_size) {
>  		unsigned long new_size = ppb->pipe_size << 1;
>  		int ret;
> @@ -164,25 +168,27 @@ out:
>  	return 0;
>  }
>  
> -static inline int try_add_page(struct page_pipe *pp, unsigned long addr)
> +static inline int try_add_page(struct page_pipe *pp, unsigned long addr,
> +			       unsigned int flags)
>  {
>  	BUG_ON(list_empty(&pp->bufs));
> -	return try_add_page_to(pp, list_entry(pp->bufs.prev, struct page_pipe_buf, l), addr);
> +	return try_add_page_to(pp, list_entry(pp->bufs.prev, struct page_pipe_buf, l), addr, flags);
>  }
>  
> -int page_pipe_add_page(struct page_pipe *pp, unsigned long addr)
> +int page_pipe_add_page(struct page_pipe *pp, unsigned long addr,
> +		       unsigned int flags)
>  {
>  	int ret;
>  
> -	ret = try_add_page(pp, addr);
> +	ret = try_add_page(pp, addr, flags);
>  	if (ret <= 0)
>  		return ret;
>  
> -	ret = page_pipe_grow(pp);
> +	ret = page_pipe_grow(pp, flags);
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = try_add_page(pp, addr);
> +	ret = try_add_page(pp, addr, flags);
>  	BUG_ON(ret > 0);
>  	return ret;
>  }
> @@ -222,8 +228,8 @@ void debug_show_page_pipe(struct page_pipe *pp)
>  	pr_debug("* %u pipes %u/%u iovs:\n",
>  			pp->nr_pipes, pp->free_iov, pp->nr_iovs);
>  	list_for_each_entry(ppb, &pp->bufs, l) {
> -		pr_debug("\tbuf %u pages, %u iovs:\n",
> -				ppb->pages_in, ppb->nr_segs);
> +		pr_debug("\tbuf %u pages, %u iovs, flags: %x :\n",
> +			 ppb->pages_in, ppb->nr_segs, ppb->flags);
>  		for (i = 0; i < ppb->nr_segs; i++) {
>  			iov = &ppb->iov[i];
>  			pr_debug("\t\t%p %lu\n", iov->iov_base, iov->iov_len / PAGE_SIZE);
> diff --git a/criu/shmem.c b/criu/shmem.c
> index 493477e..05458c7 100644
> --- a/criu/shmem.c
> +++ b/criu/shmem.c
> @@ -405,7 +405,7 @@ static int dump_one_shmem(struct shmem_info_dump *si)
>  		if (!(map[pfn] & PAGE_RSS))
>  			continue;
>  again:
> -		ret = page_pipe_add_page(pp, (unsigned long)addr + pfn * PAGE_SIZE);
> +		ret = page_pipe_add_page(pp, (unsigned long)addr + pfn * PAGE_SIZE, 0);
>  		if (ret == -EAGAIN) {
>  			ret = dump_pages(pp, &xfer, addr);
>  			if (ret)
>