Date: Tue, 16 Jan 2018 09:21:30 -0600 (CST)
From: Christopher Lameter <cl@linux.com>
To: Matthew Wilcox <willy@infradead.org>
cc: Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org,
        David Windsor <dave@nullcore.net>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-xfs@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        "David S. Miller" <davem@davemloft.net>,
        Laura Abbott <labbott@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Dave Kleikamp <dave.kleikamp@oracle.com>,
        Jan Kara <jack@suse.cz>,
        Luis de Bethencourt <luisbg@kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rik van Riel <riel@redhat.com>,
        Matthew Garrett <mjg59@google.com>,
        linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
        netdev@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy
 whitelisting)
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On Sun, 14 Jan 2018, Matthew Wilcox wrote:

> > Hmmm... At some point we should switch kmem_cache_create to pass a struct
> > containing all the parameters. Otherwise the API will blow up with
> > additional functions.
>
> Obviously I agree with you.  I'm inclined to not let that delay Kees'
> patches; we can fix the few places that use this API later.  At this
> point, my proposal for the ultimate form would be:

Right. Thats why I said "at some point"....

>
> struct kmem_cache_attr {
> 	const char name[32];

Want to avoid the string reference mess that occurred in the past?
Is that really necessary? But it would limit the size of the name.

> 	void (*ctor)(void *);
> 	unsigned int useroffset;
> 	unsigned int user_size;
> };
>
> kmem_create_cache_attr(const struct kmem_cache_attr *attr, unsigned int size,
> 			unsigned int align, slab_flags_t flags)
>
> (my rationale is that everything in attr should be const, but size, align
> and flags all get modified by the slab code).

Thought about putting all the parameters into the kmem_cache_attr struct.

So

struct kmem_cache_attr {
	char *name;
	size_t size;
	size_t align;
	slab_flags_t flags;
	unsigned int useroffset;
	unsinged int usersize;
	void (*ctor)(void *);
	kmem_isolate_func *isolate;
	kmem_migrate_func *migrate;
	...
}