linux-kernel - Re: [PATCH] shm: Fix the filename of hugetlb sysv shared memory

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Date:	Fri, 8 Jun 2007 16:55:05 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Albert Cahalan <acahalan@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	torvalds@...ux-foundation.org,
	Badari Pulavarty <pbadari@...ibm.com>
Subject: Re: [PATCH] shm: Fix the filename of hugetlb sysv shared memory

On Fri, 08 Jun 2007 17:43:34 -0600
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> Some user space tools need to identify SYSV shared memory when
> examining /proc/<pid>/maps.  To do so they look for a block device
> with major zero, a dentry named SYSV<sysv key>, and having the minor of
> the internal sysv shared memory kernel mount.
> 
> To help these tools and to make it easier for people just browsing
> /proc/<pid>/maps this patch modifies hugetlb sysv shared memory to
> use the SYSV<key> dentry naming convention.
> 
> User space tools will still have to be aware that hugetlb sysv
> shared memory lives on a different internal kernel mount and so
> has a different block device minor number from the rest of sysv
> shared memory.

I assume this fix is preferred over Badari's?  If so, why?



From: Badari Pulavarty <pbadari@...ibm.com>

shmid used to be stored as inode# for shared memory segments. Some of
the proc-ps tools use this from /proc/pid/maps.  Recent cleanups
to newseg() changed it.  This patch sets inode number back to shared
memory id to fix breakage.

Signed-off-by: Badari Pulavarty <pbadari@...ibm.com>
Cc: "Albert Cahalan" <acahalan@...il.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 ipc/shm.c |    5 +++++
 1 files changed, 5 insertions(+)

diff -puN ipc/shm.c~restore-shmid-as-inode-to-fix-proc-pid-maps-abi-breakage ipc/shm.c
--- a/ipc/shm.c~restore-shmid-as-inode-to-fix-proc-pid-maps-abi-breakage
+++ a/ipc/shm.c
@@ -397,6 +397,11 @@ static int newseg (struct ipc_namespace 
 	shp->shm_nattch = 0;
 	shp->id = shm_buildid(ns, id, shp->shm_perm.seq);
 	shp->shm_file = file;
+	/*
+	 * shmid gets reported as "inode#" in /proc/pid/maps.
+	 * proc-ps tools use this. Changing this will break them.
+	 */
+	file->f_dentry->d_inode->i_ino = shp->id;
 
 	ns->shm_tot += numpages;
 	shm_unlock(shp);
_

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