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From: jglisse@redhat.com
To: linux-mm@kvack.org
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Evgeny Baskakov" <ebaskakov@nvidia.com>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	"Mark Hairgrove" <mhairgrove@nvidia.com>
Subject: [PATCH 10/15] mm/hmm: do not differentiate between empty entry or missing directory v3
Date: Thu, 22 Mar 2018 20:55:22 -0400	[thread overview]
Message-ID: <20180323005527.758-11-jglisse@redhat.com> (raw)
In-Reply-To: <20180323005527.758-1-jglisse@redhat.com>

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.

Changed since v1:
  - Improved comments
Changed since v2:
  - Typo in comments

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@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 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

  parent reply	other threads:[~2018-03-23  0:56 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-23  0:55 [PATCH 00/15] hmm: fixes and documentations v4 jglisse
2018-03-23  0:55 ` [PATCH 01/15] mm/hmm: documentation editorial update to HMM documentation jglisse
2018-04-08  3:19   ` Randy Dunlap
2018-03-23  0:55 ` [PATCH 02/15] mm/hmm: fix header file if/else/endif maze v2 jglisse
2018-03-23  0:55 ` [PATCH 03/15] mm/hmm: HMM should have a callback before MM is destroyed v3 jglisse
2018-03-23  0:55 ` [PATCH 04/15] mm/hmm: unregister mmu_notifier when last HMM client quit v3 jglisse
2018-03-23  0:55 ` [PATCH 05/15] mm/hmm: hmm_pfns_bad() was accessing wrong struct jglisse
2018-03-23  0:55 ` [PATCH 06/15] mm/hmm: use struct for hmm_vma_fault(), hmm_vma_get_pfns() parameters v2 jglisse
2018-03-23  0:55 ` [PATCH 07/15] mm/hmm: remove HMM_PFN_READ flag and ignore peculiar architecture v2 jglisse
2018-03-23  0:55 ` [PATCH 08/15] mm/hmm: use uint64_t for HMM pfn instead of defining hmm_pfn_t to ulong v2 jglisse
2018-03-23  0:55 ` [PATCH 09/15] mm/hmm: cleanup special vma handling (VM_SPECIAL) jglisse
2018-03-23  0:55 ` jglisse [this message]
2018-03-23  0:55 ` [PATCH 11/15] mm/hmm: rename HMM_PFN_DEVICE_UNADDRESSABLE to HMM_PFN_DEVICE_PRIVATE jglisse
2018-03-23  0:55 ` [PATCH 12/15] mm/hmm: move hmm_pfns_clear() closer to where it is use jglisse
2018-03-23  0:55 ` [PATCH 13/15] mm/hmm: factor out pte and pmd handling to simplify hmm_vma_walk_pmd() v2 jglisse
2018-03-23  0:55 ` [PATCH 14/15] mm/hmm: change hmm_vma_fault() to allow write fault on page basis jglisse
2018-03-23  0:55 ` [PATCH 15/15] mm/hmm: use device driver encoding for HMM pfn v2 jglisse

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