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Thu, 07 Aug 2025 00:58:17 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: linux-mm@kvack.org, Andrew Morton Cc: Vlastimil Babka , Michal Hocko , Baoquan He , LKML , Uladzislau Rezki Subject: [PATCH 6/8] mm/vmalloc: Defer freeing partly initialized vm_struct Date: Thu, 7 Aug 2025 09:58:08 +0200 Message-Id: <20250807075810.358714-7-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250807075810.358714-1-urezki@gmail.com> References: <20250807075810.358714-1-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) Acked-by: Michal Hocko --- include/linux/vmalloc.h | 6 +++++- mm/vmalloc.c | 34 +++++++++++++++++++++++++++++++--- 2 files changed, 36 insertions(+), 4 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index fdc9aeb74a44..b1425fae8cbf 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -50,7 +50,11 @@ struct iov_iter; /* in uio.h */ #endif =20 struct vm_struct { - struct vm_struct *next; + union { + struct vm_struct *next; /* Early registration of vm_areas. */ + struct llist_node llnode; /* Asynchronous freeing on error paths. */ + }; + void *addr; unsigned long size; unsigned long flags; diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 7f48a54ec108..2424f80d524a 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3680,6 +3680,35 @@ 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 vm_struct *area, *tmp; + struct llist_node *head; + + head =3D llist_del_all(&pending_vm_area_cleanup); + if (!head) + return; + + llist_for_each_entry_safe(area, tmp, head, llnode) { + if (!area->pages) + free_vm_area(area); + else + vfree(area->addr); + } +} + +/* + * Helper for __vmalloc_area_node() to defer cleanup + * of partially initialized vm_struct in error paths. + */ +static DECLARE_WORK(cleanup_vm_area, cleanup_vm_area_work); +static void defer_vm_area_cleanup(struct vm_struct *area) +{ + if (llist_add(&area->llnode, &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) @@ -3711,8 +3740,7 @@ 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); @@ -3789,7 +3817,7 @@ 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