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Date: Thu, 22 Mar 2018 20:55:22 -0400
From: jglisse@...hat.com
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Jérôme Glisse <jglisse@...hat.com>,
Evgeny Baskakov <ebaskakov@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>,
Mark Hairgrove <mhairgrove@...dia.com>
Subject: [PATCH 10/15] mm/hmm: do not differentiate between empty entry or missing directory v3
From: Jérôme Glisse <jglisse@...hat.com>
There is no point in differentiating between a range for which there
is not even a directory (and thus entries) and empty entry (pte_none()
or pmd_none() returns true).
Simply drop the distinction ie remove HMM_PFN_EMPTY flag and merge now
duplicate hmm_vma_walk_hole() and hmm_vma_walk_clear() functions.
Changed since v1:
- Improved comments
Changed since v2:
- Typo in comments
Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Cc: Evgeny Baskakov <ebaskakov@...dia.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Mark Hairgrove <mhairgrove@...dia.com>
---
include/linux/hmm.h | 8 +++-----
mm/hmm.c | 45 +++++++++++++++------------------------------
2 files changed, 18 insertions(+), 35 deletions(-)
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 54d684fe3b90..cf283db22106 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -84,7 +84,6 @@ struct hmm;
* HMM_PFN_VALID: pfn is valid. It has, at least, read permission.
* HMM_PFN_WRITE: CPU page table has write permission set
* HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
- * HMM_PFN_EMPTY: corresponding CPU page table entry is pte_none()
* HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
* result of vm_insert_pfn() or vm_insert_page(). Therefore, it should not
* be mirrored by a device, because the entry will never have HMM_PFN_VALID
@@ -94,10 +93,9 @@ struct hmm;
#define HMM_PFN_VALID (1 << 0)
#define HMM_PFN_WRITE (1 << 1)
#define HMM_PFN_ERROR (1 << 2)
-#define HMM_PFN_EMPTY (1 << 3)
-#define HMM_PFN_SPECIAL (1 << 4)
-#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 5)
-#define HMM_PFN_SHIFT 6
+#define HMM_PFN_SPECIAL (1 << 3)
+#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 4)
+#define HMM_PFN_SHIFT 5
/*
* hmm_pfn_to_page() - return struct page pointed to by a valid HMM pfn
diff --git a/mm/hmm.c b/mm/hmm.c
index a93c1e35df91..b8affe0bf4eb 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -348,6 +348,16 @@ static void hmm_pfns_clear(uint64_t *pfns,
*pfns = 0;
}
+/*
+ * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
+ * @start: range virtual start address (inclusive)
+ * @end: range virtual end address (exclusive)
+ * @walk: mm_walk structure
+ * Returns: 0 on success, -EAGAIN after page fault, or page fault error
+ *
+ * This function will be called whenever pmd_none() or pte_none() returns true,
+ * or whenever there is no page directory covering the virtual address range.
+ */
static int hmm_vma_walk_hole(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
@@ -357,31 +367,6 @@ static int hmm_vma_walk_hole(unsigned long addr,
uint64_t *pfns = range->pfns;
unsigned long i;
- hmm_vma_walk->last = addr;
- i = (addr - range->start) >> PAGE_SHIFT;
- for (; addr < end; addr += PAGE_SIZE, i++) {
- pfns[i] = HMM_PFN_EMPTY;
- if (hmm_vma_walk->fault) {
- int ret;
-
- ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
- if (ret != -EAGAIN)
- return ret;
- }
- }
-
- return hmm_vma_walk->fault ? -EAGAIN : 0;
-}
-
-static int hmm_vma_walk_clear(unsigned long addr,
- unsigned long end,
- struct mm_walk *walk)
-{
- struct hmm_vma_walk *hmm_vma_walk = walk->private;
- struct hmm_range *range = hmm_vma_walk->range;
- uint64_t *pfns = range->pfns;
- unsigned long i;
-
hmm_vma_walk->last = addr;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++) {
@@ -440,10 +425,10 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
goto again;
if (pmd_protnone(pmd))
- return hmm_vma_walk_clear(start, end, walk);
+ return hmm_vma_walk_hole(start, end, walk);
if (write_fault && !pmd_write(pmd))
- return hmm_vma_walk_clear(start, end, walk);
+ return hmm_vma_walk_hole(start, end, walk);
pfn = pmd_pfn(pmd) + pte_index(addr);
flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
@@ -462,7 +447,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
pfns[i] = 0;
if (pte_none(pte)) {
- pfns[i] = HMM_PFN_EMPTY;
+ pfns[i] = 0;
if (hmm_vma_walk->fault)
goto fault;
continue;
@@ -513,8 +498,8 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
fault:
pte_unmap(ptep);
- /* Fault all pages in range */
- return hmm_vma_walk_clear(start, end, walk);
+ /* Fault any virtual address we were asked to fault */
+ return hmm_vma_walk_hole(start, end, walk);
}
pte_unmap(ptep - 1);
--
2.14.3
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