linux-kernel - Re: [PATCH, RFC, v2] shmat: introduce flag SHM_MAP

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Message-ID: <20081007082030.GD20740@one.firstfloor.org>
Date:	Tue, 7 Oct 2008 10:20:30 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andi Kleen <andi@...stfloor.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH, RFC, v2] shmat: introduce flag SHM_MAP_HINT

On Tue, Oct 07, 2008 at 09:57:50AM +0300, Kirill A. Shutemov wrote:
> It allows interpret attach address as a hint, not as exact address.

Please expand the description a bit. Rationale. etc.

> @@ -55,6 +55,7 @@ struct shmid_ds {
>  #define	SHM_RND		020000	/* round attach address to SHMLBA boundary */
>  #define	SHM_REMAP	040000	/* take-over region on attach */
>  #define	SHM_EXEC	0100000	/* execution access */
> +#define	SHM_MAP_HINT	0200000	/* interpret attach address as a hint */

search hint

> @@ -892,7 +892,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
>  	sfd->vm_ops = NULL;
>  
>  	down_write(&current->mm->mmap_sem);
> -	if (addr && !(shmflg & SHM_REMAP)) {
> +	if (addr && !(shmflg & (SHM_REMAP|SHM_MAP_HINT))) {

I think you were right earlier that it can be just deleted, so why don't
you just do that?

-Andi

-- 
ak@...ux.intel.com
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