linux-kernel - Re: [RFC PATCH 1/2] mm: introduce MAP_FIXED

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Message-ID: <a3f7aed9-0df2-2fd6-cebb-ba569ad66781@redhat.com>
Date:   Fri, 17 Nov 2017 08:30:48 +0100
From:   Florian Weimer <fweimer@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>, linux-api@...r.kernel.org
Cc:     Khalid Aziz <khalid.aziz@...cle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC PATCH 1/2] mm: introduce MAP_FIXED_SAFE

On 11/16/2017 11:18 AM, Michal Hocko wrote:
> +	if (flags & MAP_FIXED_SAFE) {
> +		struct vm_area_struct *vma = find_vma(mm, addr);
> +
> +		if (vma && vma->vm_start <= addr)
> +			return -ENOMEM;
> +	}

Could you pick a different error code which cannot also be caused by a 
an unrelated, possibly temporary condition?  Maybe EBUSY or EEXIST?

This would definitely help with application-based randomization of 
mappings, and there, actual ENOMEM and this error would have to be 
handled differently.

Thanks,
Florian