linux-kernel - [RESEND RFC PATCH v1 03/20] mm: add flag to __ksm

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Date:   Mon, 23 Jan 2023 09:37:31 -0800
From:   Stefan Roesch <shr@...kernel.io>
To:     linux-mm@...ck.org
Cc:     shr@...kernel.io, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: [RESEND RFC PATCH v1 03/20] mm: add flag to __ksm_exit call

This adds the flag parameter to the __ksm_exit() call. This allows to
distinguish if this call is for an prctl or madvise invocation.

Signed-off-by: Stefan Roesch <shr@...kernel.io>
---
 include/linux/ksm.h | 8 +++++---
 mm/ksm.c            | 8 ++++++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 50e6b56092f3..d38a05a36298 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -18,8 +18,8 @@
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags);
-void __ksm_exit(struct mm_struct *mm);
 int __ksm_enter(struct mm_struct *mm, int flag);
+void __ksm_exit(struct mm_struct *mm, int flag);
 
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
@@ -32,8 +32,10 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 
 static inline void ksm_exit(struct mm_struct *mm)
 {
-	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
-		__ksm_exit(mm);
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGE_ANY);
+	else if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGEABLE);
 }
 
 /*
diff --git a/mm/ksm.c b/mm/ksm.c
index d84a244fe224..83796328574c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2563,12 +2563,16 @@ int __ksm_enter(struct mm_struct *mm, int flag)
 	return 0;
 }
 
-void __ksm_exit(struct mm_struct *mm)
+void __ksm_exit(struct mm_struct *mm, int flag)
 {
 	struct ksm_mm_slot *mm_slot;
 	struct mm_slot *slot;
 	int easy_to_free = 0;
 
+	if (!(current->flags & PF_EXITING) && flag == MMF_VM_MERGE_ANY &&
+	    test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
+
 	/*
 	 * This process is exiting: if it's straightforward (as is the
 	 * case when ksmd was never running), free mm_slot immediately.
@@ -2595,7 +2599,7 @@ void __ksm_exit(struct mm_struct *mm)
 
 	if (easy_to_free) {
 		mm_slot_free(mm_slot_cache, mm_slot);
-		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+		clear_bit(flag, &mm->flags);
 		mmdrop(mm);
 	} else if (mm_slot) {
 		mmap_write_lock(mm);
-- 
2.30.2