From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaliy Gusev Subject: Re: [RFC][PATCH] Pid namespaces vs locks interaction Date: Wed, 12 Dec 2007 20:42:41 +0300 Message-ID: <200712122042.41990.vgusev@openvz.org> References: <200712061411.32159.vgusev@openvz.org> <200712121907.25283.vgusev@openvz.org> <20071212173115.GA21956@sergelap.austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: "J. Bruce Fields" , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Containers , Pavel Emelyanov To: "Serge E. Hallyn" Return-path: In-Reply-To: <20071212173115.GA21956-6s5zFf/epYLPQpwDFJZrxKsjOiXwFzmk@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On 12 December 2007 20:31:15 Serge E. Hallyn wrote: > Quoting Vitaliy Gusev (vgusev-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org): > > Hello > > > > On 6 December 2007 18:51:30 Serge E. Hallyn wrote: > > > > fl_pid is used by nfs, fuse and gfs2. For instance nfs keeps in > > > > fl_pid some unique id to identify locking process between hosts - it > > > > is not a process pid. > > > > > > Ok, but so the struct user_flock->fl_pid is being set to the task's > > > virtual pid, while the struct kernel_flock->fl_pid is being set to > > > task->tgid for nfsd use. > > > > > > Why can't nfs just generate a uniqueid from the struct pid when it > > > needs it? > > > > I think it is hard. lockd uses struct nlm_host to get process unique id > > (see __nlm_alloc_pid() function). > > Looks pretty simple though... That whole set of code could even stay > the same except for in __nlm_alloc_pid(): > > option 1: compare struct pid* instead of uint32_t pid > option 2: use the "global pid" out of the stored struct pid, > something like pid->numbers[0].nr. We can't use process pid. Process pid is circulated! NFS (lockd) needs unique process id between hosts which can't repeat oneself. > > > > Fuse just seems to copy the pid to report it to userspace, so it would > > > just copy pid_vnr(kernel_flock->pid) into user_flock->fl_pid. > > > > > > Anyway I haven't looked at all the uses of struct fl_pid, but you > > > can always get the pidnr back from the struct pid if needed so there > > > should be no problem. > > > > > > The split definately seems worthwhile to me, so that > > > user_flock->fl_pidnr can always be said to be the pid in the acting > > > process' namespace, and flock->fl_pid can always be a struct pid, > > > rather than having fl_pid sometimes be current->tgid, or sometimes > > > pid_vnr(flock->fl_nspid)... > > > > > > -serge > > > - > > > To unsubscribe from this list: send the line "unsubscribe > > > linux-fsdevel" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > > Thank, > > Vitaliy Gusev > > - > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Thank, Vitaliy Gusev