[PATCH mm-unstable v1 10/20] RDMA/umem: remove FOLL_FORCE usage

David Hildenbrand
2022-11-16T11:46:48Z

GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).

Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.

Tested-by: Leon Romanovsky <leonro@nvidia.com> # Over mlx4 and mlx5.
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/infiniband/core/umem.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 86d479772fbc..755a9c57db6f 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -156,7 +156,7 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
struct mm_struct *mm;
unsigned long npages;
int pinned, ret;
- unsigned int gup_flags = FOLL_WRITE;
+ unsigned int gup_flags = FOLL_LONGTERM;

/*
* If the combination of the addr and size requested for this memory
@@ -210,8 +210,8 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,

cur_base = addr & PAGE_MASK;

- if (!umem->writable)
- gup_flags |= FOLL_FORCE;
+ if (umem->writable)
+ gup_flags |= FOLL_WRITE;

while (npages) {
cond_resched();
@@ -219,7 +219,7 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
min_t(unsigned long, npages,
PAGE_SIZE /
sizeof(struct page *)),
- gup_flags | FOLL_LONGTERM, page_list);
+ gup_flags, page_list);
if (pinned < 0) {
ret = pinned;
goto umem_release;
--
2.38.1