From: Andrew Morton <akpm@linux-foundation.org>
To: Jaewon Kim <jaewon31.kim@samsung.com>
Cc: walken@google.com, bp@suse.de, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com
Subject: Re: [PATCH] mm: mmap: show vm_unmapped_area error log
Date: Thu, 5 Mar 2020 20:24:43 -0800 [thread overview]
Message-ID: <20200305202443.8de3598558336b1d75afbba7@linux-foundation.org> (raw)
In-Reply-To: <5E605749.9050509@samsung.com>
On Thu, 5 Mar 2020 10:35:05 +0900 Jaewon Kim <jaewon31.kim@samsung.com> wrote:
> Hello
>
> sorry for build warning.
> I've changed %d to %ld reported by kbuild.
> Let me attach full patch again below.
> --------------------------------------------------
>
>
> 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
>
hm, I suppose that could be useful. Although the choice of which info
to display could be a source of dispute. Why did you choose this info
and omit other things? Perhaps a stack trace could also be useful?
> --- 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()) {
Please avoid using printk_ratelimit(). See the comment at the
printk_ratelimit() definition site:
/*
* Please don't use printk_ratelimit(), because it shares ratelimiting state
* with all other unrelated printk_ratelimit() callsites. Instead use
* printk_ratelimited() or plain old __ratelimit().
*/
> + pr_err("%s err:%ld 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;
> }
next prev parent reply other threads:[~2020-03-06 4:24 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 ` [PATCH] mm: mmap: show vm_unmapped_area error log Jaewon Kim
2020-03-05 1:35 ` Jaewon Kim
2020-03-06 4:24 ` Andrew Morton [this message]
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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