[PATCH v10 09/25] IB/umem: use get_user_pages_fast() to pin DMA pages

John Hubbard
2019-12-12T08:20:12Z

And get rid of the mmap_sem calls, as part of that. Note
that get_user_pages_fast() will, if necessary, fall back to
__gup_longterm_unlocked(), which takes the mmap_sem as needed.

Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
drivers/infiniband/core/umem.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 7a3b99597ead..214e87aa609d 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -266,16 +266,13 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
sg = umem->sg_head.sgl;

while (npages) {
- down_read(&mm->mmap_sem);
- ret = get_user_pages(cur_base,
- min_t(unsigned long, npages,
- PAGE_SIZE / sizeof (struct page *)),
- gup_flags | FOLL_LONGTERM,
- page_list, NULL);
- if (ret < 0) {
- up_read(&mm->mmap_sem);
+ ret = get_user_pages_fast(cur_base,
+ min_t(unsigned long, npages,
+ PAGE_SIZE /
+ sizeof(struct page *)),
+ gup_flags | FOLL_LONGTERM, page_list);
+ if (ret < 0)
goto umem_release;
- }

cur_base += ret * PAGE_SIZE;
npages -= ret;
@@ -283,8 +280,6 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
sg = ib_umem_add_sg_table(sg, page_list, ret,
dma_get_max_seg_size(context->device->dma_device),
&umem->sg_nents);
-
- up_read(&mm->mmap_sem);
}

sg_mark_end(sg);
--
2.24.0