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Subject[Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*()
Date
For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

As part of this conversion, the *pte_lookup functions can be removed and
be easily replaced with get_user_pages_fast() functions. In the case of
atomic lookup, __get_user_pages_fast() is used, because it does not fall
back to the slow path: get_user_pages(). get_user_pages_fast(), on the other
hand, first calls __get_user_pages_fast(), but then falls back to the
slow path if __get_user_pages_fast() fails.

Also: remove unnecessary CONFIG_HUGETLB ifdefs.

Cc: Ira Weiny <ira.weiny@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel-mentees@lists.linuxfoundation.org
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com>
---
This is a fold of the 3 patches in the v2 patch series.
The review tags were given to the individual patches.

Changes since v3
- Used gup flags in get_user_pages_fast rather than
boolean flags.
Changes since v4
- Updated changelog according to John Hubbard.
---
drivers/misc/sgi-gru/grufault.c | 112 +++++++++-------------------------------
1 file changed, 24 insertions(+), 88 deletions(-)

diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index 4b713a8..304e9c5 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -166,96 +166,20 @@ static void get_clear_fault_map(struct gru_state *gru,
}

/*
- * Atomic (interrupt context) & non-atomic (user context) functions to
- * convert a vaddr into a physical address. The size of the page
- * is returned in pageshift.
- * returns:
- * 0 - successful
- * < 0 - error code
- * 1 - (atomic only) try again in non-atomic context
- */
-static int non_atomic_pte_lookup(struct vm_area_struct *vma,
- unsigned long vaddr, int write,
- unsigned long *paddr, int *pageshift)
-{
- struct page *page;
-
-#ifdef CONFIG_HUGETLB_PAGE
- *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT;
-#else
- *pageshift = PAGE_SHIFT;
-#endif
- if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0)
- return -EFAULT;
- *paddr = page_to_phys(page);
- put_page(page);
- return 0;
-}
-
-/*
- * atomic_pte_lookup
+ * mmap_sem is already helod on entry to this function. This guarantees
+ * existence of the page tables.
*
- * Convert a user virtual address to a physical address
* Only supports Intel large pages (2MB only) on x86_64.
- * ZZZ - hugepage support is incomplete
- *
- * NOTE: mmap_sem is already held on entry to this function. This
- * guarantees existence of the page tables.
+ * ZZZ - hugepage support is incomplete.
*/
-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;
-#ifdef CONFIG_HUGETLB_PAGE
- *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT;
-#else
- *pageshift = PAGE_SHIFT;
-#endif
- return 0;
-
-err:
- return 1;
-}
-
static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,
int write, int atomic, unsigned long *gpa, int *pageshift)
{
struct mm_struct *mm = gts->ts_mm;
struct vm_area_struct *vma;
unsigned long paddr;
- int ret, ps;
+ int ret;
+ struct page *page;

vma = find_vma(mm, vaddr);
if (!vma)
@@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr,

/*
* Atomic lookup is faster & usually works even if called in non-atomic
- * context.
+ * context. get_user_pages_fast does atomic lookup before falling back to
+ * slow gup.
*/
rmb(); /* Must/check ms_range_active before loading PTEs */
- ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps);
- if (ret) {
- if (atomic)
+ if (atomic) {
+ ret = __get_user_pages_fast(vaddr, 1, write, &page);
+ if (!ret)
goto upm;
- if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps))
+ } else {
+ ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page);
+ if (!ret)
goto inval;
}
+
+ paddr = page_to_phys(page);
+ put_user_page(page);
+
+ if (unlikely(is_vm_hugetlb_page(vma)))
+ *pageshift = HPAGE_SHIFT;
+ else
+ *pageshift = PAGE_SHIFT;
+
if (is_gru_paddr(paddr))
goto inval;
- paddr = paddr & ~((1UL << ps) - 1);
+ paddr = paddr & ~((1UL << *pageshift) - 1);
*gpa = uv_soc_phys_ram_to_gpa(paddr);
- *pageshift = ps;
+
return VTOP_SUCCESS;

inval:
--
2.7.4
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