Re: [PATCH v11 3/9] iov_iter: introduce iov_iter_get_pages_[alloc_]flags()

[Logan Gunthorpe]

On 2022-10-24 19:14, Chaitanya Kulkarni wrote:
> On 10/21/22 10:41, Logan Gunthorpe wrote:
>> Add iov_iter_get_pages_flags() and iov_iter_get_pages_alloc_flags()
>> which take a flags argument that is passed to get_user_pages_fast().
>>
>> This is so that FOLL_PCI_P2PDMA can be passed when appropriate.
>>
>> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
>> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
>> ---
>>   include/linux/uio.h |  6 ++++++
>>   lib/iov_iter.c      | 32 ++++++++++++++++++++++++--------
>>   2 files changed, 30 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/uio.h b/include/linux/uio.h
>> index 2e3134b14ffd..9ede533ce64c 100644
>> --- a/include/linux/uio.h
>> +++ b/include/linux/uio.h
>> @@ -247,8 +247,14 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode
>>   void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
>>   void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
>>   		     loff_t start, size_t count);
>> +ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
>> +		size_t maxsize, unsigned maxpages, size_t *start,
>> +		unsigned gup_flags);
>>   ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
>>   			size_t maxsize, unsigned maxpages, size_t *start);
>> +ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
>> +		struct page ***pages, size_t maxsize, size_t *start,
>> +		unsigned gup_flags);
>>   ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
>>   			size_t maxsize, size_t *start);
>>   int iov_iter_npages(const struct iov_iter *i, int maxpages);
>> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
>> index c3ca28ca68a6..53efad017f3c 100644
>> --- a/lib/iov_iter.c
>> +++ b/lib/iov_iter.c
>> @@ -1430,7 +1430,8 @@ static struct page *first_bvec_segment(const struct iov_iter *i,
>>   
>>   static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>>   		   struct page ***pages, size_t maxsize,
>> -		   unsigned int maxpages, size_t *start)
>> +		   unsigned int maxpages, size_t *start,
>> +		   unsigned int gup_flags)
>>   {
>>   	unsigned int n;
>>   
>> @@ -1442,7 +1443,6 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>>   		maxsize = MAX_RW_COUNT;
>>   
>>   	if (likely(user_backed_iter(i))) {
>> -		unsigned int gup_flags = 0;
>>   		unsigned long addr;
>>   		int res;
>>   
>> @@ -1492,33 +1492,49 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>>   	return -EFAULT;
>>   }
>>   
>> -ssize_t iov_iter_get_pages2(struct iov_iter *i,
>> +ssize_t iov_iter_get_pages(struct iov_iter *i,
>>   		   struct page **pages, size_t maxsize, unsigned maxpages,
>> -		   size_t *start)
>> +		   size_t *start, unsigned gup_flags)
>>   {
>>   	if (!maxpages)
>>   		return 0;
>>   	BUG_ON(!pages);
>>   
>> -	return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
>> +	return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages,
>> +					  start, gup_flags);
>> +}
>> +EXPORT_SYMBOL_GPL(iov_iter_get_pages);
>> +
>> +ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
>> +		size_t maxsize, unsigned maxpages, size_t *start)
>> +{
>> +	return iov_iter_get_pages(i, pages, maxsize, maxpages, start, 0);
>>   }
>>   EXPORT_SYMBOL(iov_iter_get_pages2);
>>   
>> -ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
>> +ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
>>   		   struct page ***pages, size_t maxsize,
>> -		   size_t *start)
>> +		   size_t *start, unsigned gup_flags)
>>   {
>>   	ssize_t len;
>>   
>>   	*pages = NULL;
>>   
>> -	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
>> +	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start,
>> +					 gup_flags);
>>   	if (len <= 0) {
>>   		kvfree(*pages);
>>   		*pages = NULL;
>>   	}
>>   	return len;
>>   }
>> +EXPORT_SYMBOL_GPL(iov_iter_get_pages_alloc);
>> +
>> +ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
>> +		struct page ***pages, size_t maxsize, size_t *start)
>> +{
>> +	return iov_iter_get_pages_alloc(i, pages, maxsize, start, 0);
>> +}
>>   EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
> Just one minor question why not make following functions
> EXPORT_SYMBOL_GPL() ?
> 
> 1. iov_iter_get_pages2()
> 2. iov_iter_get_pages_alloc2()

They previously were not GPL, so I didn't think that should be changed
in this patch.

Thanks for the review!

Logan