From 8c49c8c9ad98740781e5e2d30d8e20551e1a1260 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Mon, 24 Jan 2022 17:43:54 -0800 Subject: [PATCH] mm: rcu safe VMA freeing 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. Signed-off-by: Michel Lespinasse Signed-off-by: Suren Baghdasaryan --- include/linux/mm_types.h | 13 ++++++++++--- kernel/fork.c | 13 +++++++++++++ 2 files changed, 23 insertions(+), 3 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 500e536796ca..eba3987b22d8 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -444,9 +444,16 @@ 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. */ diff --git a/kernel/fork.c b/kernel/fork.c index f8ce1fc21378..a4993ac1613b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -479,10 +479,23 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) return new; } +#ifdef CONFIG_PER_VMA_LOCK +static void __vm_area_free(struct rcu_head *head) +{ + struct vm_area_struct *vma = container_of(head, struct vm_area_struct, + vm_rcu); + kmem_cache_free(vm_area_cachep, vma); +} +#endif + void vm_area_free(struct vm_area_struct *vma) { free_anon_vma_name(vma); +#ifdef CONFIG_PER_VMA_LOCK + call_rcu(&vma->vm_rcu, __vm_area_free); +#else kmem_cache_free(vm_area_cachep, vma); +#endif } static void account_kernel_stack(struct task_struct *tsk, int account) -- 2.49.0