From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH v3 hmm 09/12] mm/hmm: Poison hmm_range during unregister Date: Tue, 18 Jun 2019 15:04:22 -0300 Message-ID: <20190618180422.GK6961@ziepe.ca> References: <20190614004450.20252-1-jgg@ziepe.ca> <20190614004450.20252-10-jgg@ziepe.ca> <20190615141726.GI17724@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20190615141726.GI17724@infradead.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Christoph Hellwig Cc: Andrea Arcangeli , Philip Yang , Ralph Campbell , linux-rdma@vger.kernel.org, John Hubbard , Felix.Kuehling@amd.com, dri-devel@lists.freedesktop.org, Souptick Joarder , linux-mm@kvack.org, Jerome Glisse , amd-gfx@lists.freedesktop.org, Ira Weiny , Ben Skeggs List-Id: amd-gfx.lists.freedesktop.org T24gU2F0LCBKdW4gMTUsIDIwMTkgYXQgMDc6MTc6MjZBTSAtMDcwMCwgQ2hyaXN0b3BoIEhlbGx3 aWcgd3JvdGU6Cj4gPiAtCS8qIFNhbml0eSBjaGVjayB0aGlzIHJlYWxseSBzaG91bGQgbm90IGhh cHBlbi4gKi8KPiA+IC0JaWYgKGhtbSA9PSBOVUxMIHx8IHJhbmdlLT5lbmQgPD0gcmFuZ2UtPnN0 YXJ0KQo+ID4gLQkJcmV0dXJuOwo+ID4gLQo+ID4gIAltdXRleF9sb2NrKCZobW0tPmxvY2spOwo+ ID4gIAlsaXN0X2RlbF9yY3UoJnJhbmdlLT5saXN0KTsKPiA+ICAJbXV0ZXhfdW5sb2NrKCZobW0t PmxvY2spOwo+ID4gIAo+ID4gIAkvKiBEcm9wIHJlZmVyZW5jZSB0YWtlbiBieSBobW1fcmFuZ2Vf cmVnaXN0ZXIoKSAqLwo+ID4gLQlyYW5nZS0+dmFsaWQgPSBmYWxzZTsKPiA+ICAJbW1wdXQoaG1t LT5tbSk7Cj4gPiAgCWhtbV9wdXQoaG1tKTsKPiA+IC0JcmFuZ2UtPmhtbSA9IE5VTEw7Cj4gPiAr Cj4gPiArCS8qCj4gPiArCSAqIFRoZSByYW5nZSBpcyBub3cgaW52YWxpZCBhbmQgdGhlIHJlZiBv biB0aGUgaG1tIGlzIGRyb3BwZWQsIHNvCj4gPiArICAgICAgICAgKiBwb2lzb24gdGhlIHBvaW50 ZXIuICBMZWF2ZSBvdGhlciBmaWVsZHMgaW4gcGxhY2UsIGZvciB0aGUgY2FsbGVyJ3MKPiA+ICsg ICAgICAgICAqIHVzZS4KPiA+ICsgICAgICAgICAqLwo+ID4gKwlyYW5nZS0+dmFsaWQgPSBmYWxz ZTsKPiA+ICsJbWVtc2V0KCZyYW5nZS0+aG1tLCBQT0lTT05fSU5VU0UsIHNpemVvZihyYW5nZS0+ aG1tKSk7Cj4gCj4gRm9ybWF0dGluZyBzZWVtcyB0byBiZSBtZXNzZWQgdXAuICBCdXQgYWdhaW4g SSBkb24ndCBzZWUgdGhlIHZhbHVlCj4gaW4gdGhlIHBvaXNvbmluZywganVzdCBsZXQgbm9ybWFs IGxpbmtlZCBsaXN0IGRlYnVnZ2luZyBkbyBpdHMgd29yay4KPiBUaGUgb3RoZXIgY2xlYW51cHMg bG9va3MgZmluZSB0byBtZS4KCnRhYnMgdnMgc3BhY2VzLCBJIGZpeGVkIGl0LiBUaGlzIG9uZSBp cyBtb3JlIG11cmt5IHRoYW4gdGhlIG90aGVyIC0gaXQKaXMgdG8gcHJldmVudCB0aGUgY2FsbGVy IGZyb20gdXNpbmcgYW55IG9mIHRoZSByYW5nZSBBUElzIGFmdGVyIHRoZQpyYW5nZSBpcyB1bnJl Z2lzdGVyZWQsIGJ1dCB3ZSBjb3VsZCBhbHNvIHNhZmVseSB1c2UgTlVMTCBoZXJlLCBJCnRoaW5r LgoKSmFzb24KX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18K ZHJpLWRldmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0 dHBzOi8vbGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3100DC31E5B for ; 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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id v9sm7988792qti.60.2019.06.18.11.04.23 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 18 Jun 2019 11:04:23 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hdIT0-0003OU-LC; Tue, 18 Jun 2019 15:04:22 -0300 Date: Tue, 18 Jun 2019 15:04:22 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Souptick Joarder , Ira Weiny , Philip Yang Subject: Re: [PATCH v3 hmm 09/12] mm/hmm: Poison hmm_range during unregister Message-ID: <20190618180422.GK6961@ziepe.ca> References: <20190614004450.20252-1-jgg@ziepe.ca> <20190614004450.20252-10-jgg@ziepe.ca> <20190615141726.GI17724@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190615141726.GI17724@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Jun 15, 2019 at 07:17:26AM -0700, Christoph Hellwig wrote: > > - /* Sanity check this really should not happen. */ > > - if (hmm == NULL || range->end <= range->start) > > - return; > > - > > mutex_lock(&hmm->lock); > > list_del_rcu(&range->list); > > mutex_unlock(&hmm->lock); > > > > /* Drop reference taken by hmm_range_register() */ > > - range->valid = false; > > mmput(hmm->mm); > > hmm_put(hmm); > > - range->hmm = NULL; > > + > > + /* > > + * The range is now invalid and the ref on the hmm is dropped, so > > + * poison the pointer. Leave other fields in place, for the caller's > > + * use. > > + */ > > + range->valid = false; > > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); > > Formatting seems to be messed up. But again I don't see the value > in the poisoning, just let normal linked list debugging do its work. > The other cleanups looks fine to me. tabs vs spaces, I fixed it. This one is more murky than the other - it is to prevent the caller from using any of the range APIs after the range is unregistered, but we could also safely use NULL here, I think. Jason