linux-kernel - [PATCH RFC v2 2/4] mm/ksm: introduce ksm

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Message-Id: <20190514131654.25463-3-oleksandr@redhat.com>
Date:   Tue, 14 May 2019 15:16:52 +0200
From:   Oleksandr Natalenko <oleksandr@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Kirill Tkhai <ktkhai@...tuozzo.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Timofey Titovets <nefelim4ag@...il.com>,
        Aaron Tomlin <atomlin@...hat.com>,
        Grzegorz Halat <ghalat@...hat.com>, linux-mm@...ck.org
Subject: [PATCH RFC v2 2/4] mm/ksm: introduce ksm_leave() helper

Move MADV_UNMERGEABLE part of ksm_madvise() into a dedicated helper
since it will be further used for unmerging VMAs forcibly.

This does not bring any functional changes.

Signed-off-by: Oleksandr Natalenko <oleksandr@...hat.com>
---
 mm/ksm.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 02fdbee394cc..e9f3901168bb 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2478,6 +2478,25 @@ static int ksm_enter(struct mm_struct *mm, struct vm_area_struct *vma,
 	return 0;
 }
 
+static int ksm_leave(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end, unsigned long *vm_flags)
+{
+	int err;
+
+	if (!(*vm_flags & VM_MERGEABLE))
+		return 0;		/* just ignore the advice */
+
+	if (vma->anon_vma) {
+		err = unmerge_ksm_pages(vma, start, end);
+		if (err)
+			return err;
+	}
+
+	*vm_flags &= ~VM_MERGEABLE;
+
+	return 0;
+}
+
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags)
 {
@@ -2492,16 +2511,9 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		break;
 
 	case MADV_UNMERGEABLE:
-		if (!(*vm_flags & VM_MERGEABLE))
-			return 0;		/* just ignore the advice */
-
-		if (vma->anon_vma) {
-			err = unmerge_ksm_pages(vma, start, end);
-			if (err)
-				return err;
-		}
-
-		*vm_flags &= ~VM_MERGEABLE;
+		err = ksm_leave(vma, start, end, vm_flags);
+		if (err)
+			return err;
 		break;
 	}
 
-- 
2.21.0