*pte_lookup functions get the physical address for a given virtual
address by getting a physical page using gup and use page_to_phys to get
the physical address.
Currently, atomic_pte_lookup manually walks the page tables. If this
function fails to get a physical page, it will fall back too
non_atomic_pte_lookup to get a physical page which uses the slow gup
path to get the physical page.
Instead of manually walking the page tables use __get_user_pages_fast
which does the same thing and it does not fall back to the slow gup
path.
This is largely inspired from kvm code. kvm uses __get_user_pages_fast
in hva_to_pfn_fast function which can run in an atomic context.
Cc: Ira Weiny <ira.we...@intel.com>
Cc: John Hubbard <jhubb...@nvidia.com>
Cc: Jérôme Glisse <jgli...@redhat.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Dimitri Sivanich <sivan...@sgi.com>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux...@kvack.org
Signed-off-by: Bharath Vedartham <linux.b...@gmail.com>
---
drivers/misc/sgi-gru/grufault.c | 39 +++++----------------------------------
1 file changed, 5 insertions(+), 34 deletions(-)
diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index 75108d2..121c9a4 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -202,46 +202,17 @@ static int non_atomic_pte_lookup(struct vm_area_struct
*vma,
static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr,
int write, unsigned long *paddr, int *pageshift)
{
- pgd_t *pgdp;
- p4d_t *p4dp;
- pud_t *pudp;
- pmd_t *pmdp;
- pte_t pte;
-
- pgdp = pgd_offset(vma->vm_mm, vaddr);
- if (unlikely(pgd_none(*pgdp)))
- goto err;
-
- p4dp = p4d_offset(pgdp, vaddr);
- if (unlikely(p4d_none(*p4dp)))
- goto err;
-
- pudp = pud_offset(p4dp, vaddr);
- if (unlikely(pud_none(*pudp)))
- goto err;
+ struct page *page;
- pmdp = pmd_offset(pudp, vaddr);
- if (unlikely(pmd_none(*pmdp)))
- goto err;
-#ifdef CONFIG_X86_64
- if (unlikely(pmd_large(*pmdp)))
- pte = *(pte_t *) pmdp;
- else
-#endif
- pte = *pte_offset_kernel(pmdp, vaddr);
+ *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT;
- if (unlikely(!pte_present(pte) ||
- (write && (!pte_write(pte) || !pte_dirty(pte)))))
+ if (!__get_user_pages_fast(vaddr, 1, write, &page))
return 1;
- *paddr = pte_pfn(pte) << PAGE_SHIFT;
-
- *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT;
+ *paddr = page_to_phys(page);
+ put_user_page(page);
return 0;
-
-err:
- return 1;
}
static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,
--
2.7.4
