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

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Date:	Fri, 08 Jun 2007 09:07:54 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	"Serge E. Hallyn" <serge@...lyn.com>,
	Albert Cahalan <acahalan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	torvalds@...ux-foundation.org
Subject: Re: [RFC][PATCH] /proc/pid/maps doesn't match "ipcs -m" shmid



Eric W. Biederman wrote:

>
>At this point given that we actually have a small user space dependency
>and the fact that after I have reviewed the code it looks harmless to
>change the inode number of those inodes, in both cases they are just
>anonymous inodes generated with new_inode, and anything that we wrap
>is likely to be equally so.
>
>So it looks to me like we need to do three things:
>- Fix the inode number
>
Okay. its already done.

>
>- Fix the name on the hugetlbfs dentry to hold the key
>
I don't see need for doing this for hugetlbfs inodes. Currently, they 
don't base their
name on "key" + basing on the "key" is kind of useless anyway (its not 
unique).

>
>- Add a big fat comment that user space programs depend on this
>  behavior of both the dentry name and the inode number.
>
I don't think, the user-space can depend on the dentry-name. It can only 
depend
on inode# to match shmid. (since key is not unique esp. for key=0x00000000).

BTW, I agree that shmid is not unique even without namespaces as its 
based on
seq# and we wrap seq#.

Thanks,
Badari




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