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

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

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@deltatee.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>   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()

Reviewed-by: Chaitanya Kukkarni <kch@nvidia.com>

-ck