linux-kernel - Re: [PATCH] mm: add warning if __vm_enough

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Message-ID: <18dc0807-5596-3aad-350d-3673a033bca8@redhat.com>
Date:   Tue, 26 Jul 2022 15:45:50 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Yongqiang Liu <liuyongqiang13@...wei.com>
Subject: Re: [PATCH] mm: add warning if __vm_enough_memory fails

On 26.07.22 09:24, Kefeng Wang wrote:
> If a process has no enough memory to allocate a new virtual mapping, we
> may meet kinds of error, eg, fork cannot allocate memory, SIGBUS error
> in shmem, but it is difficult to confirm them, let's add some debug
> information to easy to check this scenario if __vm_enough_memory fails.
> 
> Reported-by: Yongqiang Liu <liuyongqiang13@...wei.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  mm/util.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/util.c b/mm/util.c
> index 1266a33a49ea..19bfff8a0ad6 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -1020,6 +1020,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
>  	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
>  		return 0;
>  error:
> +	pr_warn("%s: pid: %d, comm: %s, no enough memory for the allocation\n",
> +		__func__, current->pid, current->comm);
>  	vm_unacct_memory(pages);
>  
>  	return -ENOMEM;

Users can easily spam the kernel log, no? Maybe at least ratelimit.

-- 
Thanks,

David / dhildenb