From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750947AbcGFEDn (ORCPT ); Wed, 6 Jul 2016 00:03:43 -0400 Received: from linuxhacker.ru ([217.76.32.60]:53614 "EHLO fiona.linuxhacker.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730AbcGFEDn convert rfc822-to-8bit (ORCPT ); Wed, 6 Jul 2016 00:03:43 -0400 Subject: Re: More parallel atomic_open/d_splice_alias fun with NFS and possibly more FSes. Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=windows-1252 From: Oleg Drokin In-Reply-To: <20160706032055.GQ14480@ZenIV.linux.org.uk> Date: Tue, 5 Jul 2016 23:25:46 -0400 Cc: Mailing List , "" Content-Transfer-Encoding: 8BIT Message-Id: <6334F6B6-807C-4B36-B785-7DD502E0D70B@linuxhacker.ru> References: <20160703062917.GG14480@ZenIV.linux.org.uk> <94F1587A-7AFC-4B48-A0FC-F4CE152F18CC@linuxhacker.ru> <20160705123110.GL14480@ZenIV.linux.org.uk> <20160705135149.GM14480@ZenIV.linux.org.uk> <6D633478-6B94-465E-84D7-C0BA59C5E5F5@linuxhacker.ru> <20160705180841.GO14480@ZenIV.linux.org.uk> <1C63FC85-848B-486F-8223-F5CEB5C39848@linuxhacker.ru> <20160705200826.GP14480@ZenIV.linux.org.uk> <1587788B-C7F6-4D19-BDAD-29846231CD6C@linuxhacker.ru> <6188A470-DF7F-44CE-89F0-117EC2FA1677@linuxhacker.ru> <20160706032055.GQ14480@ZenIV.linux.org.uk> To: Al Viro X-Mailer: Apple Mail (2.1283) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Jul 5, 2016, at 11:20 PM, Al Viro wrote: > On Tue, Jul 05, 2016 at 08:29:37PM -0400, Oleg Drokin wrote: >>> + /* Otherwise we just unhash it to be rehashed afresh via >>> + * lookup if necessary >>> + */ >>> + d_drop(dentry); >> >> So we can even drop this part and retain the top condition as it was. >> d_add does not care if the dentry we are feeding it was hashed or not, >> so do you see any downsides to doing that I wonder? > > d_add() on hashed dentry will end up reaching this: > static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) > { > BUG_ON(!d_unhashed(entry)); Ah, ok. Yes, I remember about it now from the older issue with nfs. It's still puzzling why I did not hit it yet, but oh well. I wonder if handling of negative dentries broke… Time for more investigations. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from linuxhacker.ru ([217.76.32.60]:53614 "EHLO fiona.linuxhacker.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730AbcGFEDn convert rfc822-to-8bit (ORCPT ); Wed, 6 Jul 2016 00:03:43 -0400 Subject: Re: More parallel atomic_open/d_splice_alias fun with NFS and possibly more FSes. Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=windows-1252 From: Oleg Drokin In-Reply-To: <20160706032055.GQ14480@ZenIV.linux.org.uk> Date: Tue, 5 Jul 2016 23:25:46 -0400 Cc: Mailing List , "" Content-Transfer-Encoding: 8BIT Message-Id: <6334F6B6-807C-4B36-B785-7DD502E0D70B@linuxhacker.ru> References: <20160703062917.GG14480@ZenIV.linux.org.uk> <94F1587A-7AFC-4B48-A0FC-F4CE152F18CC@linuxhacker.ru> <20160705123110.GL14480@ZenIV.linux.org.uk> <20160705135149.GM14480@ZenIV.linux.org.uk> <6D633478-6B94-465E-84D7-C0BA59C5E5F5@linuxhacker.ru> <20160705180841.GO14480@ZenIV.linux.org.uk> <1C63FC85-848B-486F-8223-F5CEB5C39848@linuxhacker.ru> <20160705200826.GP14480@ZenIV.linux.org.uk> <1587788B-C7F6-4D19-BDAD-29846231CD6C@linuxhacker.ru> <6188A470-DF7F-44CE-89F0-117EC2FA1677@linuxhacker.ru> <20160706032055.GQ14480@ZenIV.linux.org.uk> To: Al Viro Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Jul 5, 2016, at 11:20 PM, Al Viro wrote: > On Tue, Jul 05, 2016 at 08:29:37PM -0400, Oleg Drokin wrote: >>> + /* Otherwise we just unhash it to be rehashed afresh via >>> + * lookup if necessary >>> + */ >>> + d_drop(dentry); >> >> So we can even drop this part and retain the top condition as it was. >> d_add does not care if the dentry we are feeding it was hashed or not, >> so do you see any downsides to doing that I wonder? > > d_add() on hashed dentry will end up reaching this: > static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) > { > BUG_ON(!d_unhashed(entry)); Ah, ok. Yes, I remember about it now from the older issue with nfs. It's still puzzling why I did not hit it yet, but oh well. I wonder if handling of negative dentries brokeďż˝ Time for more investigations.