Re: [RESEND 3/7] mm/gup: Change GUP fast to use flags rather than a write 'bool'

Dan Williams
2019-03-22T22:05:53Z

On Sun, Mar 17, 2019 at 7:36 PM <ira.weiny@intel.com> wrote:
>
> From: Ira Weiny <ira.weiny@intel.com>
>
> To facilitate additional options to get_user_pages_fast() change the
> singular write parameter to be gup_flags.
>
> This patch does not change any functionality. New functionality will
> follow in subsequent patches.
>
> Some of the get_user_pages_fast() call sites were unchanged because they
> already passed FOLL_WRITE or 0 for the write parameter.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> ---
> Changes from V1:
> Rebase to current merge tree
> arch/powerpc/mm/mmu_context_iommu.c no longer calls gup_fast
> The gup_longterm was converted in patch 1
>
> arch/mips/mm/gup.c | 11 ++++++-----
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 4 ++--
> arch/powerpc/kvm/e500_mmu.c | 2 +-
> arch/s390/kvm/interrupt.c | 2 +-
> arch/s390/mm/gup.c | 12 ++++++------
> arch/sh/mm/gup.c | 11 ++++++-----
> arch/sparc/mm/gup.c | 9 +++++----
> arch/x86/kvm/paging_tmpl.h | 2 +-
> arch/x86/kvm/svm.c | 2 +-
> drivers/fpga/dfl-afu-dma-region.c | 2 +-
> drivers/gpu/drm/via/via_dmablit.c | 3 ++-
> drivers/infiniband/hw/hfi1/user_pages.c | 3 ++-
> drivers/misc/genwqe/card_utils.c | 2 +-
> drivers/misc/vmw_vmci/vmci_host.c | 2 +-
> drivers/misc/vmw_vmci/vmci_queue_pair.c | 6 ++++--
> drivers/platform/goldfish/goldfish_pipe.c | 3 ++-
> drivers/rapidio/devices/rio_mport_cdev.c | 4 +++-
> drivers/sbus/char/oradax.c | 2 +-
> drivers/scsi/st.c | 3 ++-
> drivers/staging/gasket/gasket_page_table.c | 4 ++--
> drivers/tee/tee_shm.c | 2 +-
> drivers/vfio/vfio_iommu_spapr_tce.c | 3 ++-
> drivers/vhost/vhost.c | 2 +-
> drivers/video/fbdev/pvr2fb.c | 2 +-
> drivers/virt/fsl_hypervisor.c | 2 +-
> drivers/xen/gntdev.c | 2 +-
> fs/orangefs/orangefs-bufmap.c | 2 +-
> include/linux/mm.h | 4 ++--
> kernel/futex.c | 2 +-
> lib/iov_iter.c | 7 +++++--
> mm/gup.c | 10 +++++-----
> mm/util.c | 8 ++++----
> net/ceph/pagevec.c | 2 +-
> net/rds/info.c | 2 +-
> net/rds/rdma.c | 3 ++-
> 35 files changed, 79 insertions(+), 63 deletions(-)

>
> diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c
> index 0d14e0d8eacf..4c2b4483683c 100644
> --- a/arch/mips/mm/gup.c
> +++ b/arch/mips/mm/gup.c
> @@ -235,7 +235,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> * get_user_pages_fast() - pin user pages in memory
> * @start: starting user address
> * @nr_pages: number of pages from start to pin
> - * @write: whether pages will be written to
> + * @gup_flags: flags modifying pin behaviour
> * @pages: array that receives pointers to the pages pinned.
> * Should be at least nr_pages long.
> *
> @@ -247,8 +247,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> * requested. If nr_pages is 0 or negative, returns 0. If no pages
> * were pinned, returns -errno.
> */
> -int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> - struct page **pages)
> +int get_user_pages_fast(unsigned long start, int nr_pages,
> + unsigned int gup_flags, struct page **pages)

This looks a tad scary given all related thrash especially when it's
only 1 user that wants to do get_user_page_fast_longterm, right? Maybe
something like the following. Note I explicitly moved the flags to the
end so that someone half paying attention that calls
__get_user_pages_fast will get a compile error if they specify the
args in the same order.

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 76ba638ceda8..c6c743bc2c68 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1505,8 +1505,15 @@ static inline long
get_user_pages_longterm(unsigned long start,
}
#endif /* CONFIG_FS_DAX */

-int get_user_pages_fast(unsigned long start, int nr_pages, int write,
- struct page **pages);
+
+int __get_user_pages_fast(unsigned long start, int nr_pages,
+ struct page **pages, unsigned int gup_flags);
+
+static inline int get_user_pages_fast(unsigned long start, int
nr_pages, int write,
+ struct page **pages)
+{
+ return __get_user_pages_fast(start, nr_pages, pages, write ?
FOLL_WRITE);
+}

/* Container for pinned pfns / pages */
struct frame_vector {