| Message ID | 20221116102659.70287-12-david@redhat.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) | expand |
On Wed, Nov 16, 2022 at 11:26:50AM +0100, David Hildenbrand wrote: > 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. > > Cc: Christian Benvenuti <benve@cisco.com> > Cc: Nelson Escobar <neescoba@cisco.com> > Cc: Jason Gunthorpe <jgg@ziepe.ca> > Cc: Leon Romanovsky <leon@kernel.org> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > drivers/infiniband/hw/usnic/usnic_uiom.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Jason
diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c index 67923ced6e2d..c301b3be9f30 100644 --- a/drivers/infiniband/hw/usnic/usnic_uiom.c +++ b/drivers/infiniband/hw/usnic/usnic_uiom.c @@ -85,6 +85,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, int dmasync, struct usnic_uiom_reg *uiomr) { struct list_head *chunk_list = &uiomr->chunk_list; + unsigned int gup_flags = FOLL_LONGTERM; struct page **page_list; struct scatterlist *sg; struct usnic_uiom_chunk *chunk; @@ -96,7 +97,6 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, int off; int i; dma_addr_t pa; - unsigned int gup_flags; struct mm_struct *mm; /* @@ -131,8 +131,8 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, goto out; } - gup_flags = FOLL_WRITE; - gup_flags |= (writable) ? 0 : FOLL_FORCE; + if (writable) + gup_flags |= FOLL_WRITE; cur_base = addr & PAGE_MASK; ret = 0; @@ -140,8 +140,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, ret = pin_user_pages(cur_base, min_t(unsigned long, npages, PAGE_SIZE / sizeof(struct page *)), - gup_flags | FOLL_LONGTERM, - page_list, NULL); + gup_flags, page_list, NULL); if (ret < 0) goto out;
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. Cc: Christian Benvenuti <benve@cisco.com> Cc: Nelson Escobar <neescoba@cisco.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Leon Romanovsky <leon@kernel.org> Signed-off-by: David Hildenbrand <david@redhat.com> --- drivers/infiniband/hw/usnic/usnic_uiom.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)