From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-194.mimecast.com ([63.128.21.194]:45777 "EHLO us-smtp-delivery-194.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754846AbdEKMQn (ORCPT ); Thu, 11 May 2017 08:16:43 -0400 From: Trond Myklebust To: "mhocko@kernel.org" , "n.borisov.lkml@gmail.com" CC: "torvalds@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-nfs@vger.kernel.org" Subject: Re: [GIT PULL] Please pull NFS client fixes for 4.12 Date: Thu, 11 May 2017 12:16:37 +0000 Message-ID: <1494504995.3207.1.camel@primarydata.com> References: <1494434821.4764.1.camel@primarydata.com> <20170511075910.GD26782@dhcp22.suse.cz> In-Reply-To: <20170511075910.GD26782@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: T24gVGh1LCAyMDE3LTA1LTExIGF0IDA5OjU5ICswMjAwLCBNaWNoYWwgSG9ja28gd3JvdGU6DQo+ IE9uIFRodSAxMS0wNS0xNyAxMDo1MzoyNywgTmlrb2xheSBCb3Jpc292IHdyb3RlOg0KPiA+IA0K PiA+IA0KPiA+IE9uIDEwLjA1LjIwMTcgMTk6NDcsIFRyb25kIE15a2xlYnVzdCB3cm90ZToNCj4g DQo+IFsuLi5dDQo+ID4gPiAtIENsZWFudXAgYW5kIHJlbW92YWwgb2Ygc29tZSBtZW1vcnkgZmFp bHVyZSBwYXRocyBub3cgdGhhdA0KPiA+ID4gwqAgR0ZQX05PRlMgaXMgZ3VhcmFudGVlZCB0byBu ZXZlciBmYWlsLg0KPiA+IA0KPiA+IFdoYXQgZ3VhcmFudGVlcyB0aGF0PyBTaW5jZSBpZiB0aGlz IGlzIHRoZSBjYXNlIHRoZW4gdGhpcyBjYW4NCj4gPiByZXN1bHQgaW4NCj4gPiBhIGxvdCBvZiBv cHBvcnR1bml0aWVzIGZvciBjbGVhbnVwIGFjcm9zcyB0aGUgd2hvbGUga2VybmVsIHRyZWUuDQo+ ID4gQWZ0ZXINCj4gPiBkaXNjdXNzaW5nIHdpdGggbWhvY2tvIChjYydlZCkgaXQgc2VlbXMgdGhh dCBpbiBwcmFjdGljZSBldmVyeXRoaW5nDQo+ID4gYmVsb3cgQ09TVExZX09SREVSIHdoaWNoIGFy ZSBub3QgR0ZQX05PUkVUUlkgd2lsbCBuZXZlciBmYWlsLiBCdXQNCj4gPiB0aGlzDQo+ID4gc2Vt YW50aWMgaXMgbm90IHRoZSBzYW1lIGFzIEdGUF9OT0ZBSUwuIEUuZy4gbm90aGluZyBndWFyYW50 ZWVzDQo+ID4gdGhhdA0KPiA+IHRoaXMgd2lsbCBzdGF5IGxpa2UgdGhhdCBpbiB0aGUgZnV0dXJl Pw0KPiANCj4gSW4gcHJhY3RpY2UgaXQgaXMgaGFyZCB0byBjaGFuZ2UgdGhlIHNlbWFudGljIG9m IHNtYWxsIGFsbG9jYXRpb25zDQo+IG5ldmVyDQo+IGZhaWwgX3ByYWN0aWNhbGx5Xy4gQnV0IHRo aXMgaXMgYWJzb2x1dGVseSBub3QgZ3VhcmFudGVlZCEgVGhleSBjYW4NCj4gZmFpbA0KPiBlLmcu IHdoZW4gdGhlIGFsbG9jYXRpb24gY29udGV4dCBpcyB0aGUgb29tIHZpY3RpbS4gUmVtb3Zpbmcg ZXJyb3INCj4gcGF0aHMNCj4gZm9yIGFsbG9jYXRpb24gZmFpbHVyZXMgaXMganVzdCB3cm9uZy4N Cg0KT0ssIHRoaXMgbWFrZXMgbm8gZnVja2luZyBzZW5zZSBhdCBhbGwuDQoNCkVpdGhlciBhbGxv Y2F0aW9ucyBjYW4gZmFpbCBvciB0aGV5IGNhbid0Lg0KMSkgSWYgdGhleSBjYW4ndCBmYWlsLCB0 aGVuIHdlIGRvbid0IG5lZWQgdGhlIGNoZWNrcy4NCjIpIElmIHRoZXkgY2FuIGZhaWwsIHRoZW4g d2UgZG8gbmVlZCB0aGVtLCBhbmQgdGhpcyBoYW5kIHdyaW5naW5nIGluDQp0aGUgTU0gY29tbXVu aXR5IGFib3V0IEdGUF8qIHNlbWFudGljcyBhbmQgaG93IHdlIG5lZWQgdG8gcHJldmVudA0KZmFp bHVyZSBpcyBmdWNraW5nIHBvaW50bGVzcy4NCg0KU28gd2hpY2ggaXMgaXQ/ICgxKSBvciAoMik/ DQoNCg0KDQoNCi0tIA0KVHJvbmQgTXlrbGVidXN0DQpMaW51eCBORlMgY2xpZW50IG1haW50YWlu ZXIsIFByaW1hcnlEYXRhDQp0cm9uZC5teWtsZWJ1c3RAcHJpbWFyeWRhdGEuY29tDQo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932590AbdEKMQp (ORCPT ); Thu, 11 May 2017 08:16:45 -0400 Received: from us-smtp-delivery-194.mimecast.com ([63.128.21.194]:59393 "EHLO us-smtp-delivery-194.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754911AbdEKMQn (ORCPT ); Thu, 11 May 2017 08:16:43 -0400 From: Trond Myklebust To: "mhocko@kernel.org" , "n.borisov.lkml@gmail.com" CC: "torvalds@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-nfs@vger.kernel.org" Subject: Re: [GIT PULL] Please pull NFS client fixes for 4.12 Thread-Topic: [GIT PULL] Please pull NFS client fixes for 4.12 Thread-Index: AQHSya0NrD4QrM982UyDRv5+dS7+KaHuw/6AgAABmoCAAEfrgA== Date: Thu, 11 May 2017 12:16:37 +0000 Message-ID: <1494504995.3207.1.camel@primarydata.com> References: <1494434821.4764.1.camel@primarydata.com> <20170511075910.GD26782@dhcp22.suse.cz> In-Reply-To: <20170511075910.GD26782@dhcp22.suse.cz> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [68.49.162.121] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MWHPR11MB1358;7:B8VMZEX73epNB92wXtCvJ0o8gt0KwjhZHedkRT0UlVvp0jKbw0VkJnXUml4snzZzGUqeIz7gb0yn/EDKE+3VOLJA1zWXDKFXlK86mf5f3WGpcAprDK3auzVfNz2ImNE1QvCY0U/a77yl8ldpmx/vmNGB6tsWU1uLXe+R6tFgYl8y3/Zs9QW2bxa2VEW1vsKxn5kXzhb7SbAww134CUfIos+3fFGPVeqoerkOzhnfYe09k7GBPFNufxdOk444UmE9MHd9t6Wmqb/kXHbPe7emepzzwi7rOOpgwgPVW7jzFGYxKXocLO4Kbe4gA3XzifRPefcIsqQBUPG/Ay20YnRZrQ==;20:f5lCiYLCcRew5SsJ1FPYQKSEVqn5L2yr6kCqmFom7/UIohrqpmh4kXXSygw52+XekWxCAK2u/EDmqoCheaALJfMULuy6i43ksO7t1KrbF1U3jyqckLpvBK2Gdl98bV9ppGaU5YSTDm2gUsdWEJBwj1YRKb7SsNOu1bZLUaz5pM4= x-ms-office365-filtering-correlation-id: 43d4dc90-9c71-46c1-b616-08d4986792a6 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(2017030254075)(201703131423075);SRVR:MWHPR11MB1358; 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spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-ID: MIME-Version: 1.0 X-OriginatorOrg: primarydata.com X-MS-Exchange-CrossTenant-originalarrivaltime: 11 May 2017 12:16:37.2832 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 03193ed6-8726-4bb3-a832-18ab0d28adb7 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR11MB1358 X-MC-Unique: v6WbjWGRODyyoznOQ5558w-1 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id v4BCGnh7025861 On Thu, 2017-05-11 at 09:59 +0200, Michal Hocko wrote: > On Thu 11-05-17 10:53:27, Nikolay Borisov wrote: > > > > > > On 10.05.2017 19:47, Trond Myklebust wrote: > > [...] > > > - Cleanup and removal of some memory failure paths now that > > >   GFP_NOFS is guaranteed to never fail. > > > > What guarantees that? Since if this is the case then this can > > result in > > a lot of opportunities for cleanup across the whole kernel tree. > > After > > discussing with mhocko (cc'ed) it seems that in practice everything > > below COSTLY_ORDER which are not GFP_NORETRY will never fail. But > > this > > semantic is not the same as GFP_NOFAIL. E.g. nothing guarantees > > that > > this will stay like that in the future? > > In practice it is hard to change the semantic of small allocations > never > fail _practically_. But this is absolutely not guaranteed! They can > fail > e.g. when the allocation context is the oom victim. Removing error > paths > for allocation failures is just wrong. OK, this makes no fucking sense at all. Either allocations can fail or they can't. 1) If they can't fail, then we don't need the checks. 2) If they can fail, then we do need them, and this hand wringing in the MM community about GFP_* semantics and how we need to prevent failure is fucking pointless. So which is it? (1) or (2)? -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@primarydata.com