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Subject[PATCH 09/14] mm/hmm: do not differentiate between empty entry or missing directory
Date
From: Jérôme Glisse <jglisse@redhat.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.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.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 78b3ed6d7977..6d2b6bf6da4b 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -84,7 +84,6 @@ struct hmm;
* HMM_PFN_VALID: pfn is valid
* 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 04595a994542..2118e42cb838 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -305,6 +305,16 @@ static void hmm_pfns_clear(uint64_t *pfns,
*pfns = 0;
}

+/*
+ * hmm_vma_walk_hole() - handle a range back by no pmd or no pte
+ * @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 is an helper call whenever pmd_none() or pte_none() returns true
+ * or when there is no directory covering the range.
+ */
static int hmm_vma_walk_hole(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
@@ -314,31 +324,6 @@ 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++) {
@@ -397,10 +382,10 @@ 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;
@@ -419,7 +404,7 @@ 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;
@@ -470,8 +455,8 @@ 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 all pages in range if ask for */
+ return hmm_vma_walk_hole(start, end, walk);
}
pte_unmap(ptep - 1);

--
2.14.3
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