linux-kernel - [PATCH 5/5] mm/vmalloc.c: return explicit error value in alloc_vmap

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Message-ID: <20250415023952.27850-6-bhe@redhat.com>
Date: Tue, 15 Apr 2025 10:39:52 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-mm@...ck.org
Cc: akpm@...ux-foundation.org,
	urezki@...il.com,
	linux-kernel@...r.kernel.org,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH 5/5] mm/vmalloc.c: return explicit error value in alloc_vmap_area()

In codes of alloc_vmap_area(), it returns the upper bound 'vend' to
indicate if the allocation is successful or failed. That is not very clear.

Here change to return explicit error values and check them to judge if
allocation is successful.

IS_ERR_VALUE already uses unlikely() internally

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/vmalloc.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3f38a232663b..5b21cd09b2b4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1715,7 +1715,7 @@ va_clip(struct rb_root *root, struct list_head *head,
 			 */
 			lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT);
 			if (!lva)
-				return -1;
+				return -ENOMEM;
 		}
 
 		/*
@@ -1729,7 +1729,7 @@ va_clip(struct rb_root *root, struct list_head *head,
 		 */
 		va->va_start = nva_start_addr + size;
 	} else {
-		return -1;
+		return -EINVAL;
 	}
 
 	if (type != FL_FIT_TYPE) {
@@ -1758,19 +1758,19 @@ va_alloc(struct vmap_area *va,
 
 	/* Check the "vend" restriction. */
 	if (nva_start_addr + size > vend)
-		return vend;
+		return -ERANGE;
 
 	/* Update the free vmap_area. */
 	ret = va_clip(root, head, va, nva_start_addr, size);
-	if (WARN_ON_ONCE(ret))
-		return vend;
+	if (ret)
+		return ret;
 
 	return nva_start_addr;
 }
 
 /*
  * Returns a start address of the newly allocated area, if success.
- * Otherwise a vend is returned that indicates failure.
+ * Otherwise an error value is returned that indicates failure.
  */
 static __always_inline unsigned long
 __alloc_vmap_area(struct rb_root *root, struct list_head *head,
@@ -1795,14 +1795,13 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
 
 	va = find_vmap_lowest_match(root, size, align, vstart, adjust_search_size);
 	if (unlikely(!va))
-		return vend;
+		return -ENOENT;
 
 	nva_start_addr = va_alloc(va, root, head, size, align, vstart, vend);
-	if (nva_start_addr == vend)
-		return vend;
 
 #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
-	find_vmap_lowest_match_check(root, head, size, align);
+	if (!IS_ERR_VALUE(nva_start_addr))
+		find_vmap_lowest_match_check(root, head, size, align);
 #endif
 
 	return nva_start_addr;
@@ -1932,7 +1931,7 @@ node_alloc(unsigned long size, unsigned long align,
 	struct vmap_area *va;
 
 	*vn_id = 0;
-	*addr = vend;
+	*addr = -EINVAL;
 
 	/*
 	 * Fallback to a global heap if not vmalloc or there
@@ -2012,20 +2011,20 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	}
 
 retry:
-	if (addr == vend) {
+	if (IS_ERR_VALUE(addr)) {
 		preload_this_cpu_lock(&free_vmap_area_lock, gfp_mask, node);
 		addr = __alloc_vmap_area(&free_vmap_area_root, &free_vmap_area_list,
 			size, align, vstart, vend);
 		spin_unlock(&free_vmap_area_lock);
 	}
 
-	trace_alloc_vmap_area(addr, size, align, vstart, vend, addr == vend);
+	trace_alloc_vmap_area(addr, size, align, vstart, vend, IS_ERR_VALUE(addr));
 
 	/*
-	 * If an allocation fails, the "vend" address is
+	 * If an allocation fails, the error value is
 	 * returned. Therefore trigger the overflow path.
 	 */
-	if (unlikely(addr == vend))
+	if (IS_ERR_VALUE(addr))
 		goto overflow;
 
 	va->va_start = addr;
@@ -4753,9 +4752,10 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
 
 		ret = va_clip(&free_vmap_area_root,
 			&free_vmap_area_list, va, start, size);
-		if (WARN_ON_ONCE(unlikely(ret)))
-			/* It is a BUG(), but trigger recovery instead. */
+		if ((unlikely(ret))) {
+			WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret);
 			goto recovery;
+		}
 
 		/* Allocated area. */
 		va = vas[area];
-- 
2.41.0