Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756636AbZIUPa7 (ORCPT ); Mon, 21 Sep 2009 11:30:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756617AbZIUPa7 (ORCPT ); Mon, 21 Sep 2009 11:30:59 -0400 Received: from mail-yw0-f194.google.com ([209.85.211.194]:37528 "EHLO mail-yw0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755198AbZIUPa5 convert rfc822-to-8bit (ORCPT ); Mon, 21 Sep 2009 11:30:57 -0400 X-Greylist: delayed 4389 seconds by postgrey-1.27 at vger.kernel.org; Mon, 21 Sep 2009 11:30:57 EDT DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=U88/W0Pjb6N5vxuMwRR5USlar7/7LowDxtZn3blP/MrNjrei/WYlB9MROFAaDndth9 vSfJjz5IaPkkzu2xvzBKw4ueyIjzD4nQhtjPO2bgEUbDGCUfQP/nJLPt1ZKBDVqWQcjw fUA5Bn6ESyaynMc+gRAq04CyRa/Imb3mIRPAU= MIME-Version: 1.0 In-Reply-To: <20090921143857.GE14381@ZenIV.linux.org.uk> References: <20090921140220.GD14381@ZenIV.linux.org.uk> <8bd0f97a0909210710h5bb75bcdwb666b51a9155a70a@mail.gmail.com> <20090921143857.GE14381@ZenIV.linux.org.uk> From: Mike Frysinger Date: Mon, 21 Sep 2009 11:30:41 -0400 Message-ID: <8bd0f97a0909210830j80df616m1fee64108c0125a7@mail.gmail.com> Subject: Re: [PATCH 2/2] vfs: fix d_path() for unreachable paths To: Al Viro Cc: Miklos Szeredi , akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Valdis.Kletnieks@vt.edu, agruen@suse.de, hch@lst.de, hugh.dickins@tiscali.co.uk, matthew@wil.cx Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1888 Lines: 44 On Mon, Sep 21, 2009 at 10:38, Al Viro wrote: > On Mon, Sep 21, 2009 at 10:10:17AM -0400, Mike Frysinger wrote: >> it works without having to copy & paste the same exact structures over >> and over.  a suggestion as how to do it cleanly without bloating the >> code is certainly welcome.  it doesnt really matter that it's on the >> stack as the usage is small and d_path() is given the size of the >> buffer, so it isnt going to overflow. > > Umm...  Surely, you can put a CPU number + one bit into PDE->data?  As in >        proc_create_data("icplb", ....., (void *)(cpu * 2)) >        proc_create_data("dcplb", ....., (void *)(cpu * 2 + 1)) > and >        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); >        unsigned long n = (unsigned long) pde->data; >        ... >        cpu = n / 2; >        is_D = n & 1; if i'd known this route, i'd have used it ;). i'll look into changing it, thanks. >> > ??For another... locking in that loop >> > over processes and VMAs of each looks very suspicios, while we are at it. >> >> we've reviewed it several times and exercised it in multiple ways.  so >> unless you have a real idea of something being wrong, the code has >> been vetted heavily. > > write_lock_irq tasklist_lock > loop over processes >        get_task_mm [now VM is pinned down, but not locked] >        walk the VMA list without any locking > > Something on another CPU (you have SMP systems, judging by the previously > discussed code, right?) does munmap(). the SMP port is limited due to lack of hardware cache coherency, but we'll check out this call path -mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/