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

Chaitanya Kulkarni
2022-10-25T01:14:18Z

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