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Mon, 29 Aug 2022 14:25:39 -0700 (PDT) Date: Mon, 29 Aug 2022 21:25:05 +0000 In-Reply-To: <20220829212531.3184856-1-surenb@google.com> Mime-Version: 1.0 References: <20220829212531.3184856-1-surenb@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220829212531.3184856-3-surenb@google.com> Subject: [RFC PATCH 02/28] mm: rcu safe VMA freeing From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, paulmck@kernel.org, riel@surriel.com, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, surenb@google.com, kernel-team@android.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org X-ccpol: medium X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220829_142540_676244_482E0566 X-CRM114-Status: GOOD ( 14.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Michel Lespinasse 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 | 16 +++++++++++----- kernel/fork.c | 13 +++++++++++++ 2 files changed, 24 insertions(+), 5 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index cf97f3884fda..bed25ef7c994 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -403,12 +403,18 @@ 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, vm_end; - /* linked list of VM areas per task, sorted by address */ - struct vm_area_struct *vm_next, *vm_prev; + /* linked list of VMAs per task, sorted by address */ + struct vm_area_struct *vm_next, *vm_prev; + }; +#ifdef CONFIG_PER_VMA_LOCK + struct rcu_head vm_rcu; /* Used for deferred freeing. */ +#endif + }; struct rb_node vm_rb; diff --git a/kernel/fork.c b/kernel/fork.c index 90c85b17bf69..614872438393 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -481,10 +481,23 @@ 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)