linux-kernel - Re: [RFC][PATCH] /proc/pid/maps doesn't match "ipcs -m" shmid

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Date:	Fri, 8 Jun 2007 00:41:45 -0400
From:	"Albert Cahalan" <acahalan@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	pbadari@...ibm.com, torvalds@...ux-foundation.org
Subject: Re: [RFC][PATCH] /proc/pid/maps doesn't match "ipcs -m" shmid

On 6/7/07, Eric W. Biederman <ebiederm@...ssion.com> wrote:

> So it looks to me like we need to do three things:
> - Fix the inode number
> - Fix the name on the hugetlbfs dentry to hold the key
> - Add a big fat comment that user space programs depend on this
>   behavior of both the dentry name and the inode number.

Assuming that this proposed fix goes in:

Since the inode number is the shmid, and this is a number
that the kernel randomly chooses AFAIK, there should be
no need to have different shm segments sharing the same
inode number.

The situation with the key is a bit more disturbing, though
we already hit that anyway when IPC_PRIVATE is used.
(why anybody would NOT use IPC_PRIVATE is a mystery)
So having the key in the name doesn't make things worse.

I have some concern about the device minor number.
This should be the same for all shm mappings; I do not
know if the behavior changed.
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