linux-kernel - [PATCH 5/5] mm/vmalloc: improve allocation failure error messages

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Date:   Tue, 26 Jan 2021 14:54:04 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Nicholas Piggin <npiggin@...il.com>, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>
Subject: [PATCH 5/5] mm/vmalloc: improve allocation failure error messages

There are several reasons why a vmalloc can fail, virtual space
exhausted, page array allocation failure, page allocation failure,
and kernel page table allocation failure.

Add distinct warning messages for the main causes of failure, with
some added information like page order or allocation size where
applicable.

Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
 mm/vmalloc.c | 40 ++++++++++++++++++++++++++++------------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5ff190590fe4..4facf582a3be 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2790,6 +2790,10 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 
 	if (!pages) {
 		free_vm_area(area);
+		warn_alloc(gfp_mask, NULL,
+			   "vmalloc size %lu allocation failure: "
+			   "page array size %lu allocation failed",
+			   area->nr_pages * PAGE_SIZE, array_size);
 		return NULL;
 	}
 
@@ -2813,6 +2817,10 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 			/* Successfully allocated i pages, free them in __vfree() */
 			area->nr_pages = i;
 			atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
+			warn_alloc(gfp_mask, NULL,
+				   "vmalloc size %lu allocation failure: "
+				   "page order %u allocation failed",
+				   area->nr_pages * PAGE_SIZE, page_order);
 			goto fail;
 		}
 
@@ -2824,15 +2832,17 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	}
 	atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
 
-	if (vmap_pages_range(addr, addr + size, prot, pages, page_shift) < 0)
+	if (vmap_pages_range(addr, addr + size, prot, pages, page_shift) < 0) {
+		warn_alloc(gfp_mask, NULL,
+			   "vmalloc size %lu allocation failure: "
+			   "failed to map pages",
+			   area->nr_pages * PAGE_SIZE);
 		goto fail;
+	}
 
 	return area->addr;
 
 fail:
-	warn_alloc(gfp_mask, NULL,
-			  "vmalloc: allocation failure, allocated %ld of %ld bytes",
-			  (area->nr_pages*PAGE_SIZE), size);
 	__vfree(area->addr);
 	return NULL;
 }
@@ -2866,8 +2876,15 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	unsigned long real_align = align;
 	unsigned int shift = PAGE_SHIFT;
 
-	if (!size || (size >> PAGE_SHIFT) > totalram_pages())
-		goto fail;
+	if (WARN_ON_ONCE(!size))
+		return NULL;
+
+	if ((size >> PAGE_SHIFT) > totalram_pages()) {
+		warn_alloc(gfp_mask, NULL,
+			   "vmalloc size %lu allocation failure: "
+			   "exceeds total pages", real_size);
+		return NULL;
+	}
 
 	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP) &&
 			arch_vmap_pmd_supported(prot)) {
@@ -2894,8 +2911,12 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	size = PAGE_ALIGN(size);
 	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
 				vm_flags, start, end, node, gfp_mask, caller);
-	if (!area)
+	if (!area) {
+		warn_alloc(gfp_mask, NULL,
+			   "vmalloc size %lu allocation failure: "
+			   "vm_struct allocation failed", real_size);
 		goto fail;
+	}
 
 	addr = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
 	if (!addr)
@@ -2920,11 +2941,6 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		goto again;
 	}
 
-	if (!area) {
-		/* Warn for area allocation, page allocations already warn */
-		warn_alloc(gfp_mask, NULL,
-			  "vmalloc: allocation failure: %lu bytes", real_size);
-	}
 	return NULL;
 }
 
-- 
2.23.0