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From: Alistair Popple <apopple@nvidia.com>
To: <linux-mm@kvack.org>, <nouveau@lists.freedesktop.org>,
	<bskeggs@redhat.com>, <akpm@linux-foundation.org>
Cc: rcampbell@nvidia.com, linux-doc@vger.kernel.org,
	Alistair Popple <apopple@nvidia.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	kvm-ppc@vger.kernel.org
Subject: [Nouveau] [PATCH v4 3/8] mm/rmap: Split try_to_munlock from try_to_unmap
Date: Thu, 4 Mar 2021 17:16:40 +1100
Message-ID: <20210304061645.29747-4-apopple@nvidia.com> (raw)
In-Reply-To: <20210304061645.29747-1-apopple@nvidia.com>

The behaviour of try_to_unmap_one() is difficult to follow because it
performs different operations based on a fairly large set of flags used
in different combinations.

TTU_MUNLOCK is one such flag. However it is exclusively used by
try_to_munlock() which specifies no other flags. Therefore rather than
overload try_to_unmap_one() with unrelated behaviour split this out into
it's own function and remove the flag.

Signed-off-by: Alistair Popple <apopple@nvidia.com>

---

Christoph - I didn't add your Reviewed-by because removal of the extra
VM_LOCKED check changed things slightly. Let me know if you're still ok
for me to add it. Thanks.

v4:
* Removed redundant check for VM_LOCKED
---
 include/linux/rmap.h |  1 -
 mm/rmap.c            | 40 ++++++++++++++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 70085ca1a3fc..7f1ee411bd7b 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -87,7 +87,6 @@ struct anon_vma_chain {
 
 enum ttu_flags {
 	TTU_MIGRATION		= 0x1,	/* migration mode */
-	TTU_MUNLOCK		= 0x2,	/* munlock mode */
 
 	TTU_SPLIT_HUGE_PMD	= 0x4,	/* split huge PMD if any */
 	TTU_IGNORE_MLOCK	= 0x8,	/* ignore mlock */
diff --git a/mm/rmap.c b/mm/rmap.c
index ef9ef2694c58..c8a637abffb3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1391,10 +1391,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 	struct mmu_notifier_range range;
 	enum ttu_flags flags = (enum ttu_flags)(long)arg;
 
-	/* munlock has nothing to gain from examining un-locked vmas */
-	if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
-		return true;
-
 	if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
 	    is_zone_device_page(page) && !is_device_private_page(page))
 		return true;
@@ -1455,8 +1451,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 				page_vma_mapped_walk_done(&pvmw);
 				break;
 			}
-			if (flags & TTU_MUNLOCK)
-				continue;
 		}
 
 		/* Unexpected PMD-mapped THP? */
@@ -1775,6 +1769,37 @@ static int page_not_mapped(struct page *page)
 	return !page_mapped(page);
 };
 
+static bool try_to_munlock_one(struct page *page, struct vm_area_struct *vma,
+		     unsigned long address, void *arg)
+{
+	struct page_vma_mapped_walk pvmw = {
+		.page = page,
+		.vma = vma,
+		.address = address,
+	};
+
+	/* munlock has nothing to gain from examining un-locked vmas */
+	if (!(vma->vm_flags & VM_LOCKED))
+		return true;
+
+	while (page_vma_mapped_walk(&pvmw)) {
+		/* PTE-mapped THP are never mlocked */
+		if (!PageTransCompound(page)) {
+			/*
+			 * Holding pte lock, we do *not* need
+			 * mmap_lock here
+			 */
+			mlock_vma_page(page);
+		}
+		page_vma_mapped_walk_done(&pvmw);
+
+		/* found a mlocked page, no point continuing munlock check */
+		return false;
+	}
+
+	return true;
+}
+
 /**
  * try_to_munlock - try to munlock a page
  * @page: the page to be munlocked
@@ -1787,8 +1812,7 @@ static int page_not_mapped(struct page *page)
 void try_to_munlock(struct page *page)
 {
 	struct rmap_walk_control rwc = {
-		.rmap_one = try_to_unmap_one,
-		.arg = (void *)TTU_MUNLOCK,
+		.rmap_one = try_to_munlock_one,
 		.done = page_not_mapped,
 		.anon_lock = page_lock_anon_vma_read,
 
-- 
2.20.1

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  parent reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04  6:16 [Nouveau] [PATCH v4 0/8] Add support for SVM atomics in Nouveau Alistair Popple
2021-03-04  6:16 ` [Nouveau] [PATCH v4 1/8] mm: Remove special swap entry functions Alistair Popple
2021-03-08 18:24   ` Ralph Campbell
2021-03-04  6:16 ` [Nouveau] [PATCH v4 2/8] mm/swapops: Rework swap entry manipulation code Alistair Popple
2021-03-08 18:30   ` Ralph Campbell
2021-03-04  6:16 ` Alistair Popple [this message]
2021-03-08 18:39   ` [Nouveau] [PATCH v4 3/8] mm/rmap: Split try_to_munlock from try_to_unmap Ralph Campbell
2021-03-04  6:16 ` [Nouveau] [PATCH v4 4/8] mm/rmap: Split migration into its own function Alistair Popple
2021-03-08 18:58   ` Ralph Campbell
2021-03-09  0:01     ` Alistair Popple
2021-03-04  6:16 ` [Nouveau] [PATCH v4 5/8] mm: Device exclusive memory access Alistair Popple
2021-03-08 19:44   ` Ralph Campbell
2021-03-09  1:17     ` Alistair Popple
2021-03-04  6:16 ` [Nouveau] [PATCH v4 6/8] mm: Selftests for exclusive device memory Alistair Popple
2021-03-04  6:16 ` [Nouveau] [PATCH v4 7/8] nouveau/svm: Refactor nouveau_range_fault Alistair Popple
2021-03-04  6:16 ` [Nouveau] [PATCH v4 8/8] nouveau/svm: Implement atomic SVM access Alistair Popple

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