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From: Jaewon Kim <jaewon31.kim@samsung.com>
To: walken@google.com, bp@suse.de, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	jaewon31.kim@gmail.com, Jaewon Kim <jaewon31.kim@samsung.com>
Subject: [PATCH] mm: mmap: show vm_unmapped_area error log
Date: Wed,  4 Mar 2020 12:02:06 +0900	[thread overview]
Message-ID: <20200304030206.1706-1-jaewon31.kim@samsung.com> (raw)
In-Reply-To: CGME20200304030211epcas1p4da8cb569947aefb3aad1da039aaabce4@epcas1p4.samsung.com

Even on 64 bit kernel, the mmap failure can happen for a 32 bit task.
Virtual memory space shortage of a task on mmap is reported to userspace
as -ENOMEM. It can be confused as physical memory shortage of overall
system.

The vm_unmapped_area can be called to by some drivers or other kernel
core system like filesystem. It can be hard to know which code layer
returns the -ENOMEM.

Print error log of vm_unmapped_area with rate limited. Without rate
limited, soft lockup ocurrs on infinite mmap sytem call.

i.e.)
<3>[  576.024088]  [6:  mmap_infinite:14251] mmap: vm_unmapped_area err:-12 total_vm:0xfee08 flags:0x1 len:0xa00000 low:0x8000 high:0xf3f63000

Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
---
 include/linux/mm.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 52269e56c514..ee822d65ebb7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2379,10 +2379,19 @@ extern unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info);
 static inline unsigned long
 vm_unmapped_area(struct vm_unmapped_area_info *info)
 {
+	unsigned long addr;
+
 	if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
-		return unmapped_area_topdown(info);
+		addr = unmapped_area_topdown(info);
 	else
-		return unmapped_area(info);
+		addr = unmapped_area(info);
+
+	if (IS_ERR_VALUE(addr) && printk_ratelimit()) {
+		pr_err("%s err:%d total_vm:0x%lx flags:0x%lx len:0x%lx low:0x%lx high:0x%lx\n",
+			__func__, addr, current->mm->total_vm, info->flags,
+			info->length, info->low_limit, info->high_limit);
+	}
+	return addr;
 }
 
 /* truncate.c */
-- 
2.13.7



       reply	other threads:[~2020-03-04  3:02 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200304030211epcas1p4da8cb569947aefb3aad1da039aaabce4@epcas1p4.samsung.com>
2020-03-04  3:02 ` Jaewon Kim [this message]
2020-03-05  1:35   ` [PATCH] mm: mmap: show vm_unmapped_area error log Jaewon Kim
2020-03-06  4:24     ` Andrew Morton
2020-03-06  6:16       ` Jaewon Kim
2020-03-07 23:47         ` Andrew Morton
2020-03-08  1:58           ` Matthew Wilcox
2020-03-08  9:58             ` Jaewon Kim
2020-03-08 12:36               ` Matthew Wilcox
2020-03-09  9:12                 ` Jaewon Kim
2020-03-09 14:01                   ` Matthew Wilcox
2020-03-10  4:18                     ` Jaewon Kim
2020-03-08 10:10           ` Jaewon Kim

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