+ mm-rcu-safe-vma-freeing.patch added to mm-unstable branch

+ mm-rcu-safe-vma-freeing.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: rcu safe VMA freeing
has been added to the -mm mm-unstable branch.  Its filename is
     mm-rcu-safe-vma-freeing.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rcu-safe-vma-freeing.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Michel Lespinasse <michel@lespinasse.org>
Subject: mm: rcu safe VMA freeing
Date: Mon, 27 Feb 2023 09:36:09 -0800

This prepares for page faults handling under VMA lock, looking up VMAs
under protection of an rcu read lock, instead of the usual mmap read lock.

Link: https://lkml.kernel.org/r/20230227173632.3292573-11-surenb@google.com
Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/include/linux/mm_types.h~mm-rcu-safe-vma-freeing
+++ a/include/linux/mm_types.h
@@ -480,9 +480,16 @@ struct anon_vma_name {
 struct vm_area_struct {
 	/* The first cache line has the info for VMA tree walking. */
 
-	unsigned long vm_start;		/* Our start address within vm_mm. */
-	unsigned long vm_end;		/* The first byte after our end address
-					   within vm_mm. */
+	union {
+		struct {
+			/* VMA covers [vm_start; vm_end) addresses within mm */
+			unsigned long vm_start;
+			unsigned long vm_end;
+		};
+#ifdef CONFIG_PER_VMA_LOCK
+		struct rcu_head vm_rcu;	/* Used for deferred freeing. */
+#endif
+	};
 
 	struct mm_struct *vm_mm;	/* The address space we belong to. */
 
--- a/kernel/fork.c~mm-rcu-safe-vma-freeing
+++ a/kernel/fork.c
@@ -479,12 +479,30 @@ struct vm_area_struct *vm_area_dup(struc
 	return new;
 }
 
-void vm_area_free(struct vm_area_struct *vma)
+static void __vm_area_free(struct vm_area_struct *vma)
 {
 	free_anon_vma_name(vma);
 	kmem_cache_free(vm_area_cachep, vma);
 }
 
+#ifdef CONFIG_PER_VMA_LOCK
+static void vm_area_free_rcu_cb(struct rcu_head *head)
+{
+	struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
+						  vm_rcu);
+	__vm_area_free(vma);
+}
+#endif
+
+void vm_area_free(struct vm_area_struct *vma)
+{
+#ifdef CONFIG_PER_VMA_LOCK
+	call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb);
+#else
+	__vm_area_free(vma);
+#endif
+}
+
 static void account_kernel_stack(struct task_struct *tsk, int account)
 {
 	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
_

Patches currently in -mm which might be from michel@lespinasse.org are

mm-rcu-safe-vma-freeing.patch