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Mon, 28 Sep 2026 10:41:51 -0700 (PDT) Date: Mon, 28 Sep 2026 17:41:11 +0000 In-Reply-To: <20260928174122.3380703-1-smostafa@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260928174122.3380703-1-smostafa@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260928174122.3380703-5-smostafa@google.com> Subject: [RFC PATCH 04/15] fork: Separate vmap stack allocation and free calls From: Mostafa Saleh To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, akpm@linux-foundation.org, urezki@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, kees@kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, gustavoars@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, Pasha Tatashin , Linus Walleij , David Stevens , Mostafa Saleh Content-Type: text/plain; charset="UTF-8" From: Pasha Tatashin In preparation for the partially populated stacks, separate out the __vmalloc_node and vfree calls from the vmap based stack allocations. Signed-off-by: Pasha Tatashin [Fix a bug in original patch: free_vmap_stack(vm_area->addr)] Signed-off-by: Linus Walleij [Add missing free_vmap_stack conversion, fix typos, rebase] Signed-off-by: David Stevens [Resolved conflict in alloc_thread_stack_node(), update commit msg] Signed-off-by: Mostafa Saleh --- kernel/fork.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 473878d7f62f..3f1c46d8f7ec 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -272,6 +272,21 @@ static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area) return false; } +static inline struct vm_struct *alloc_vmap_stack(int node) +{ + void *stack; + + stack = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_VMAP_STACK, + node, __builtin_return_address(0)); + + return stack ? find_vm_area(stack) : NULL; +} + +static inline void free_vmap_stack(struct vm_struct *vm_area) +{ + vfree(vm_area->addr); +} + static void thread_stack_free_rcu(struct rcu_head *rh) { struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu); @@ -280,7 +295,7 @@ static void thread_stack_free_rcu(struct rcu_head *rh) if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area)) return; - vfree(vm_area->addr); + free_vmap_stack(vm_area); } static void thread_stack_delayed_free(struct task_struct *tsk) @@ -307,7 +322,7 @@ static int free_vm_stack_cache(unsigned int cpu) if (!vm_area) continue; - vfree(vm_area->addr); + free_vmap_stack(vm_area); cached_vm_stack_areas[i] = NULL; } @@ -336,14 +351,14 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm_area) static int alloc_thread_stack_node(struct task_struct *tsk, int node) { struct vm_struct *vm_area; - void *stack; vm_area = alloc_thread_stack_node_from_cache(tsk, node); if (vm_area) { unsigned long offset = 0; + void *stack; if (memcg_charge_kernel_stack(vm_area)) { - vfree(vm_area->addr); + free_vmap_stack(vm_area); return -ENOMEM; } @@ -364,15 +379,12 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) return 0; } - stack = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, - GFP_VMAP_STACK, - node, __builtin_return_address(0)); - if (!stack) + vm_area = alloc_vmap_stack(node); + if (!vm_area) return -ENOMEM; - vm_area = find_vm_area(stack); if (memcg_charge_kernel_stack(vm_area)) { - vfree(stack); + free_vmap_stack(vm_area); return -ENOMEM; } /* @@ -381,8 +393,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) * so cache the vm_struct. */ tsk->stack_vm_area = vm_area; - stack = kasan_reset_tag(stack); - tsk->stack = stack; + tsk->stack = kasan_reset_tag(vm_area->addr); return 0; } -- 2.56.0.rc1.315.gc6ed9934b7-goog