From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e3.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id l57MsMNF025594 for ; Thu, 7 Jun 2007 18:54:22 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l57Nuxxp526676 for ; Thu, 7 Jun 2007 19:56:59 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l57NuwMG025140 for ; Thu, 7 Jun 2007 19:56:58 -0400 Message-ID: <46689B55.1020905@us.ibm.com> Date: Thu, 07 Jun 2007 16:57:09 -0700 From: Badari Pulavarty MIME-Version: 1.0 Subject: Re: [RFC][PATCH] /proc/pid/maps doesn't match "ipcs -m" shmid References: <20070606204432.b670a7b1.akpm@linux-foundation.org> <787b0d920706062153u7ad64179p1c4f3f663c3882f@mail.gmail.com> <1181233393.9995.14.camel@dyn9047017100.beaverton.ibm.com> <787b0d920706070943h6ac65b85nee5b01600905be08@mail.gmail.com> <1181235997.9995.23.camel@dyn9047017100.beaverton.ibm.com> <20070607124824.27e909fd.akpm@linux-foundation.org> <1181246363.9995.37.camel@dyn9047017100.beaverton.ibm.com> <20070607203757.GA531@vino.hallyn.com> <1181250968.9995.41.camel@dyn9047017100.beaverton.ibm.com> <20070607220820.GA1191@vino.hallyn.com> <20070607222246.GB1191@vino.hallyn.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: "Serge E. Hallyn" Cc: Andrew Morton , Albert Cahalan , lkml , linux-mm , ebiederm@xmission.com, torvalds@linux-foundation.org List-ID: Serge E. Hallyn wrote: >Quoting Serge E. Hallyn (serge@hallyn.com): > >>Quoting Badari Pulavarty (pbadari@us.ibm.com): >> >>>On Thu, 2007-06-07 at 15:37 -0500, Serge E. Hallyn wrote: >>> >>>>Quoting Badari Pulavarty (pbadari@us.ibm.com): >>>> >>>>>On Thu, 2007-06-07 at 12:48 -0700, Andrew Morton wrote: >>>>> >>>>>>On Thu, 07 Jun 2007 10:06:37 -0700 >>>>>>Badari Pulavarty wrote: >>>>>> >>>>>>>On Thu, 2007-06-07 at 12:43 -0400, Albert Cahalan wrote: >>>>>>> >>>>>>>>On 6/7/07, Badari Pulavarty wrote: >>>>>>>> >>>>>>>>>BTW, I agree with Eric that its would be nice to use shmid as part >>>>>>>>>of name instead of forcing to be as inode number. It should be >>>>>>>>>possible for pmap to workout shmid from "key" or name. Isn't it ? >>>>>>>>> >>>>>>>>It is not at all nice. >>>>>>>> >>>>>>>>1. it's incompatible ABI breakage >>>>>>>>2. where will you put the key then, in the inode? :-) >>>>>>>> >>>>>>>Nope. Currently "key" is part of the name (but its not unique). >>>>>>> >>>>>>>>Changing to "SYSVID%d" is no good either. Look, people >>>>>>>>are ***parsing*** this stuff in /proc. The /proc filesystem >>>>>>>>is not some random sandbox to be playing in. >>>>>>>> >>>>>>>>Before you go messing with it, note that the device number >>>>>>>>also matters. (it's per-boot dynamic, but that's OK) >>>>>>>>That's how one knows that /SYSV00000000 is not just >>>>>>>>a regular file; sadly these didn't get a non-/ prefix. >>>>>>>>(and no you can't fix that now; it's way too late) >>>>>>>> >>>>>>>>Next time you feel like breaking an ABI, mind putting >>>>>>>>"LET'S BREAK AN ABI!" in the subject of your email? >>>>>>>> >>>>>>>I am not breaking ABI. Its already broken in the current >>>>>>>mainline. I am trying to fix it by putting back the ino# >>>>>>>as shmid. Eric had a suggestion that, instead of depending >>>>>>>on the inode# to be shmid, we could embed shmid into name >>>>>>>(instead of "key" which is currently not unique). >>>>>>> >>>>>>>>BTW, I suspect this kind of thing also breaks: >>>>>>>>a. fuser, lsof, and other resource usage display tools >>>>>>>>b. various obscure emulators (similar to valgrind) >>>>>>>> >>>>>>>If you strongly feel that "old" behaviour needs to be retained, >>>>>>> >>>>>>yup, we should put it back. The change was, afaik, accidental. >>>>>> >>>>>>>here is the patch I originally suggested. >>>>>>> >>>>>>Confused. Will this one-liner fix all the userspace breakage to which >>>>>>Albert refers? >>>>>> >>>>>Yes. Albert, please correct me if I am wrong. >>>>> >>>>It will, but could lead to two different inodes with the same i_ino, >>>>right? >>>> >>>Only if we generate same ID in two different namespaces. Is it currently >>>possible ? >>> >>Should be nothing stopping it. >> > >(just to be more certain, a quick test showed I can get id 0 for >different keys, and different ids for the same key 0xff, in different >ipc namespaces) > Funny. I played with it and decided that it can happen :) Thanks, Badari -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org