linux-kernel - Re: [PATCH v16 06/11] mm: introduce memfd_secret system call to create "secret" memory areas

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Message-ID: <YBqT/nwFpfP2EyeJ@dhcp22.suse.cz>
Date:   Wed, 3 Feb 2021 13:15:58 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org, Hagen Paul Pfeifer <hagen@...u.net>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v16 06/11] mm: introduce memfd_secret system call to
 create "secret" memory areas

On Thu 21-01-21 14:27:18, Mike Rapoport wrote:
> +static struct file *secretmem_file_create(unsigned long flags)
> +{
> +	struct file *file = ERR_PTR(-ENOMEM);
> +	struct secretmem_ctx *ctx;
> +	struct inode *inode;
> +
> +	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
> +	if (IS_ERR(inode))
> +		return ERR_CAST(inode);
> +
> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		goto err_free_inode;
> +
> +	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
> +				 O_RDWR, &secretmem_fops);
> +	if (IS_ERR(file))
> +		goto err_free_ctx;
> +
> +	mapping_set_unevictable(inode->i_mapping);

Btw. you need also mapping_set_gfp_mask(mapping, GFP_HIGHUSER) because
the default is GFP_HIGHUSER_MOVABLE and you do not support migration so
no pages from movable zones should be allowed.

-- 
Michal Hocko
SUSE Labs