[CRIU] [PATCH 1/5] page-server: Introduce page_server_start_sync_read

[Pavel Emelyanov]

On 06/14/2017 02:51 PM, Mike Rapoport wrote:
> On Wed, Jun 14, 2017 at 01:14:28PM +0300, Pavel Emelyanov wrote:
>> There's no need in two API calls to read xfer header
>> and pages themselves, so merge them into one single
>> call.
>>
>> Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
>> ---
>>  criu/include/page-xfer.h |  3 +--
>>  criu/page-xfer.c         | 22 ++++++++++++++++++++--
>>  criu/pagemap.c           | 14 ++------------
>>  3 files changed, 23 insertions(+), 16 deletions(-)
>>
>> diff --git a/criu/include/page-xfer.h b/criu/include/page-xfer.h
>> index 0b92ec9..5d8dc81 100644
>> --- a/criu/include/page-xfer.h
>> +++ b/criu/include/page-xfer.h
>> @@ -60,11 +60,10 @@ extern int check_parent_page_xfer(int fd_type, long id);
>>  
>>  /* async request/receive of remote pages */
>>  extern int request_remote_pages(int pid, unsigned long addr, int nr_pages);
>> -extern int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid);
>> -extern int receive_remote_pages(int len, void *buf);
>>  
>>  typedef int (*ps_async_read_complete)(int pid, unsigned long vaddr, int nr_pages, void *);
>>  extern int page_server_start_async_read(void *buf, int nr_pages,
>>  		ps_async_read_complete complete, void *priv);
>> +extern int page_server_start_sync_read(void *buf, int nr_pages, unsigned long *vaddr);
>>  
>>  #endif /* __CR_PAGE_XFER__H__ */
>> diff --git a/criu/page-xfer.c b/criu/page-xfer.c
>> index c557407..761985a 100644
>> --- a/criu/page-xfer.c
>> +++ b/criu/page-xfer.c
>> @@ -1174,7 +1174,7 @@ int request_remote_pages(int pid, unsigned long addr, int nr_pages)
>>  	return 0;
>>  }
>>  
>> -int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>> +static int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>>  {
>>  	struct page_server_iov pi;
>>  
>> @@ -1194,7 +1194,7 @@ int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>>  	return 0;
>>  }
>>  
>> -int receive_remote_pages(int len, void *buf)
>> +static int receive_remote_pages(int len, void *buf)
>>  {
>>  	if (recv(page_server_sk, buf, len, MSG_WAITALL) != len) {
>>  		pr_perror("Failed to receive page data");
>> @@ -1203,3 +1203,21 @@ int receive_remote_pages(int len, void *buf)
>>  
>>  	return 0;
>>  }
>> +
>> +int page_server_start_sync_read(void *buf, int nr, unsigned long *vaddr)
>> +{
>> +	int ret, pid, new_nr;
>> +
>> +	/*
>> +	 * Note, that for async remote page_read, the actual
>> +	 * transfer happens in the lazy-pages daemon
>> +	 */
>> +	ret = receive_remote_pages_info(&new_nr, vaddr, &pid);
>> +	if (ret == 0) {
>> +		if (new_nr < 0 || new_nr > nr)
>> +			return -1;
> 
> To be completely on the safe side we should also take care of the case when
> new_nr < nr. 

True, but isn't it the case for async reader too? I thought it was and planned
to add the respective checks in the next series.

> With current implementation of remote lazy-pages this should
> not happen because both dump and restore sides see identical iovecs, but we
> may extend usage of read_page_remote, e.g. for the image-less case
> (--remote). I think adding
> 
> nr = new_nr;
> 
> here will do the right thing.
> 
>> +		ret = receive_remote_pages(nr * PAGE_SIZE, buf);
>> +	}
>> +
>> +	return ret;
>> +}
>> diff --git a/criu/pagemap.c b/criu/pagemap.c
>> index d770e81..06264a1 100644
>> --- a/criu/pagemap.c
>> +++ b/criu/pagemap.c
>> @@ -466,7 +466,7 @@ static int read_page_complete(int pid, unsigned long vaddr, int nr_pages, void *
>>  static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
>>  				  int nr, void *buf, unsigned flags)
>>  {
>> -	int ret, pid, new_nr;
>> +	int ret;
>>  
>>  	/* We always do PR_ASAP mode here (FIXME?) */
>>  	ret = request_remote_pages(pr->pid, vaddr, nr);
>> @@ -475,17 +475,7 @@ static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
>>  	if (flags & PR_ASYNC)
>>  		return page_server_start_async_read(buf, nr, read_page_complete, pr);
>>  
>> -	/*
>> -	 * Note, that for async remote page_read, the actual
>> -	 * transfer happens in the lazy-pages daemon
>> -	 */
>> -	ret = receive_remote_pages_info(&new_nr, &vaddr, &pid);
>> -	if (ret == 0) {
>> -		if (new_nr < 0 || new_nr > nr)
>> -			return -1;
>> -		ret = receive_remote_pages(nr * PAGE_SIZE, buf);
>> -	}
>> -
>> +	ret = page_server_start_sync_read(buf, nr, &vaddr);
>>  	if (ret == 0 && pr->io_complete)
>>  		ret = pr->io_complete(pr, vaddr, nr);
>>  
>> -- 
>> 2.1.4
>>
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> .
>