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Fri, 04 Jul 2025 08:25:43 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: linux-mm@kvack.org, Andrew Morton Cc: Michal Hocko , LKML , Baoquan He , Uladzislau Rezki Subject: [RFC 5/7] mm/vmalloc: Defer freeing partly initialized vm_struct Date: Fri, 4 Jul 2025 17:25:35 +0200 Message-Id: <20250704152537.55724-6-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250704152537.55724-1-urezki@gmail.com> References: <20250704152537.55724-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" __vmalloc_area_node() may call free_vmap_area() or vfree() on error paths, both of which can sleep. This becomes problematic if the function is invoked from an atomic context, such as when GFP_ATOMIC or GFP_NOWAIT is passed via gfp_mask. To fix this, unify error paths and defer the cleanup of partly initialized vm_struct objects to a workqueue. This ensures that freeing happens in a process context and avoids invalid sleeps in atomic regions. Signed-off-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5bac15b09b03..2eaff0575a9e 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3677,6 +3677,36 @@ vm_area_alloc_pages(gfp_t gfp, int nid, return nr_allocated; } =20 +static LLIST_HEAD(pending_vm_area_cleanup); + +static void cleanup_vm_area_work(struct work_struct *work) +{ + struct llist_node *node, *next; + struct vm_struct *vm; + + llist_for_each_safe(node, next, llist_del_all(&pending_vm_area_cleanup)) { + vm =3D (void *) node - offsetof(struct vm_struct, next); + + if (!vm->nr_pages) + free_vm_area(vm); + else + vfree(vm->addr); + } +} + +static DECLARE_WORK(cleanup_vm_area, cleanup_vm_area_work); + +/* + * Helper for __vmalloc_area_node() to defer cleanup + * of partially initialized vm_struct in error paths. + */ +static void +defer_vm_area_cleanup(struct vm_struct *area) +{ + if (llist_add((struct llist_node *) &area->next, &pending_vm_area_cleanup= )) + schedule_work(&cleanup_vm_area); +} + static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot, unsigned int page_shift, int node) @@ -3708,8 +3738,7 @@ static void *__vmalloc_area_node(struct vm_struct *ar= ea, gfp_t gfp_mask, warn_alloc(gfp_mask, NULL, "vmalloc error: size %lu, failed to allocated page array size %lu", nr_small_pages * PAGE_SIZE, array_size); - free_vm_area(area); - return NULL; + goto fail; } =20 set_vm_area_page_order(area, page_shift - PAGE_SHIFT); @@ -3786,7 +3815,7 @@ static void *__vmalloc_area_node(struct vm_struct *ar= ea, gfp_t gfp_mask, return area->addr; =20 fail: - vfree(area->addr); + defer_vm_area_cleanup(area); return NULL; } =20 --=20 2.39.5