linux-kernel - [PATCH v2 05/10] mm/vmalloc: Defer freeing partly initialized vm

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Message-ID: <20250915134041.151462-6-urezki@gmail.com>
Date: Mon, 15 Sep 2025 15:40:35 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...nel.org>,
	Baoquan He <bhe@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Michal Hocko <mhocko@...e.com>
Subject: [PATCH v2 05/10] mm/vmalloc: Defer freeing partly initialized vm_struct

__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.

Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 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 2759dac6be44..97252078a3dc 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -50,7 +50,11 @@ struct iov_iter;		/* in uio.h */
 #endif
 
 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 b77e8be75f10..e61e62872372 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3686,6 +3686,35 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 	return nr_allocated;
 }
 
+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 = 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)
@@ -3717,8 +3746,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, 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;
 	}
 
 	set_vm_area_page_order(area, page_shift - PAGE_SHIFT);
@@ -3795,7 +3823,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	return area->addr;
 
 fail:
-	vfree(area->addr);
+	defer_vm_area_cleanup(area);
 	return NULL;
 }
 
-- 
2.47.3