*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.
Also, the function atomic_pte_lookup's return value has been changed to boolean.
The callsites have been appropriately modified.
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.weiny@xxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx>
---
Changes since v2
- Modified the return value of atomic_pte_lookup
to use booleans rather than numeric values.
This was suggested by John Hubbard.
---
drivers/misc/sgi-gru/grufault.c | 56 +++++++++++------------------------------
1 file changed, 15 insertions(+), 41 deletions(-)
diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index bce47af..da2d2cc 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -193,9 +193,11 @@ static int non_atomic_pte_lookup(struct vm_area_struct *vma,
}
/*
- * atomic_pte_lookup
+ * atomic_pte_lookup() - Convert a user virtual address
+ * to a physical address.
+ * @Return: true for success, false for failure. Failure means that
+ * the page could not be pinned via gup fast.
*
- * Convert a user virtual address to a physical address
* Only supports Intel large pages (2MB only) on x86_64.
* ZZZ - hugepage support is incomplete
*
@@ -205,49 +207,20 @@ 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;
-
- 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);
-
- if (unlikely(!pte_present(pte) ||
- (write && (!pte_write(pte) || !pte_dirty(pte)))))
- return 1;
-
- *paddr = pte_pfn(pte) << PAGE_SHIFT;
+ struct page *page;
if (unlikely(is_vm_hugetlb_page(vma)))
*pageshift = HPAGE_SHIFT;
else
*pageshift = PAGE_SHIFT;
- return 0;
+ if (!__get_user_pages_fast(vaddr, 1, write, &page))
+ return false;
-err:
- return 1;
+ *paddr = page_to_phys(page);
+ put_user_page(page);
+
+ return true;
}
static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,
@@ -256,7 +229,8 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,
struct mm_struct *mm = gts->ts_mm;
struct vm_area_struct *vma;
unsigned long paddr;
- int ret, ps;
+ int ps;
+ bool success;
vma = find_vma(mm, vaddr);
if (!vma)
@@ -267,8 +241,8 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,
* context.
*/
rmb(); /* Must/check ms_range_active before loading PTEs */
- ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps);
- if (ret) {
+ success = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps);
+ if (!success) {
if (atomic)
goto upm;
if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps))
--
2.7.4
