From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: [PATCH v3 hmm 04/12] mm/hmm: Simplify hmm_get_or_create and make it reliable Date: Thu, 13 Jun 2019 21:44:42 -0300 Message-ID: <20190614004450.20252-5-jgg@ziepe.ca> References: <20190614004450.20252-1-jgg@ziepe.ca> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20190614004450.20252-1-jgg@ziepe.ca> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Cc: Andrea Arcangeli , Philip Yang , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, linux-mm@kvack.org, Jason Gunthorpe , dri-devel@lists.freedesktop.org, Ira Weiny , Ben Skeggs List-Id: linux-rdma@vger.kernel.org RnJvbTogSmFzb24gR3VudGhvcnBlIDxqZ2dAbWVsbGFub3guY29tPgoKQXMgY29kZWQgdGhpcyBm dW5jdGlvbiBjYW4gZmFsc2UtZmFpbCBpbiB2YXJpb3VzIHJhY3kgc2l0dWF0aW9ucy4gTWFrZSBp dApyZWxpYWJsZSBhbmQgc2ltcGxlciBieSBydW5uaW5nIHVuZGVyIHRoZSB3cml0ZSBzaWRlIG9m IHRoZSBtbWFwX3NlbSBhbmQKYXZvaWRpbmcgdGhlIGZhbHNlLWZhaWxpbmcgY29tcGFyZS9leGNo YW5nZSBwYXR0ZXJuLiBEdWUgdG8gdGhlIG1tYXBfc2VtCnRoaXMgbm8gbG9uZ2VyIGhhcyB0byBh dm9pZCByYWNpbmcgd2l0aCBhIDJuZCBwYXJhbGxlbApobW1fZ2V0X29yX2NyZWF0ZSgpLgoKVW5m b3J0dW5hdGVseSB0aGlzIHN0aWxsIGhhcyB0byB1c2UgdGhlIHBhZ2VfdGFibGVfbG9jayBhcyB0 aGUKbm9uLXNsZWVwaW5nIGxvY2sgcHJvdGVjdGluZyBtbS0+aG1tLCBzaW5jZSB0aGUgY29udGV4 dHMgd2hlcmUgd2UgZnJlZSB0aGUKaG1tIGFyZSBpbmNvbXBhdGlibGUgd2l0aCBtbWFwX3NlbS4K ClNpZ25lZC1vZmYtYnk6IEphc29uIEd1bnRob3JwZSA8amdnQG1lbGxhbm94LmNvbT4KUmV2aWV3 ZWQtYnk6IEpvaG4gSHViYmFyZCA8amh1YmJhcmRAbnZpZGlhLmNvbT4KUmV2aWV3ZWQtYnk6IFJh bHBoIENhbXBiZWxsIDxyY2FtcGJlbGxAbnZpZGlhLmNvbT4KUmV2aWV3ZWQtYnk6IElyYSBXZWlu eSA8aXJhLndlaW55QGludGVsLmNvbT4KVGVzdGVkLWJ5OiBQaGlsaXAgWWFuZyA8UGhpbGlwLllh bmdAYW1kLmNvbT4KLS0tCnYyOgotIEZpeCBlcnJvciB1bndpbmQgb2YgbW1ncmFiIChKZXJvbWUp Ci0gVXNlIGhtbSBsb2NhbCBpbnN0ZWFkIG9mIDJuZCBjb250YWluZXJfb2YgKEplcm9tZSkKdjM6 Ci0gQ2FuJ3QgdXNlIG1tYXBfc2VtIGluIHRoZSBTUkNVIGNhbGxiYWNrLCBrZWVwIHVzaW5nIHRo ZQogIHBhZ2VfdGFibGVfbG9jayAoUGhpbGlwKQotLS0KIG1tL2htbS5jIHwgODQgKysrKysrKysr KysrKysrKysrKysrKysrLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0KIDEgZmlsZSBj aGFuZ2VkLCAzNiBpbnNlcnRpb25zKCspLCA0OCBkZWxldGlvbnMoLSkKCmRpZmYgLS1naXQgYS9t bS9obW0uYyBiL21tL2htbS5jCmluZGV4IDA4MGIxN2EyZTg3ZTJkLi40YzY0ZDRjMzJmNDgyNSAx MDA2NDQKLS0tIGEvbW0vaG1tLmMKKysrIGIvbW0vaG1tLmMKQEAgLTMxLDE2ICszMSw2IEBACiAj aWYgSVNfRU5BQkxFRChDT05GSUdfSE1NX01JUlJPUikKIHN0YXRpYyBjb25zdCBzdHJ1Y3QgbW11 X25vdGlmaWVyX29wcyBobW1fbW11X25vdGlmaWVyX29wczsKIAotc3RhdGljIGlubGluZSBzdHJ1 Y3QgaG1tICptbV9nZXRfaG1tKHN0cnVjdCBtbV9zdHJ1Y3QgKm1tKQotewotCXN0cnVjdCBobW0g KmhtbSA9IFJFQURfT05DRShtbS0+aG1tKTsKLQotCWlmIChobW0gJiYga3JlZl9nZXRfdW5sZXNz X3plcm8oJmhtbS0+a3JlZikpCi0JCXJldHVybiBobW07Ci0KLQlyZXR1cm4gTlVMTDsKLX0KLQog LyoqCiAgKiBobW1fZ2V0X29yX2NyZWF0ZSAtIHJlZ2lzdGVyIEhNTSBhZ2FpbnN0IGFuIG1tIChI TU0gaW50ZXJuYWwpCiAgKgpAQCAtNTUsMTEgKzQ1LDE5IEBAIHN0YXRpYyBpbmxpbmUgc3RydWN0 IGhtbSAqbW1fZ2V0X2htbShzdHJ1Y3QgbW1fc3RydWN0ICptbSkKICAqLwogc3RhdGljIHN0cnVj dCBobW0gKmhtbV9nZXRfb3JfY3JlYXRlKHN0cnVjdCBtbV9zdHJ1Y3QgKm1tKQogewotCXN0cnVj dCBobW0gKmhtbSA9IG1tX2dldF9obW0obW0pOwotCWJvb2wgY2xlYW51cCA9IGZhbHNlOworCXN0 cnVjdCBobW0gKmhtbTsKIAotCWlmIChobW0pCi0JCXJldHVybiBobW07CisJbG9ja2RlcF9hc3Nl cnRfaGVsZF9leGNsdXNpdmUoJm1tLT5tbWFwX3NlbSk7CisKKwkvKiBBYnVzZSB0aGUgcGFnZV90 YWJsZV9sb2NrIHRvIGFsc28gcHJvdGVjdCBtbS0+aG1tLiAqLworCXNwaW5fbG9jaygmbW0tPnBh Z2VfdGFibGVfbG9jayk7CisJaWYgKG1tLT5obW0pIHsKKwkJaWYgKGtyZWZfZ2V0X3VubGVzc196 ZXJvKCZtbS0+aG1tLT5rcmVmKSkgeworCQkJc3Bpbl91bmxvY2soJm1tLT5wYWdlX3RhYmxlX2xv Y2spOworCQkJcmV0dXJuIG1tLT5obW07CisJCX0KKwl9CisJc3Bpbl91bmxvY2soJm1tLT5wYWdl X3RhYmxlX2xvY2spOwogCiAJaG1tID0ga21hbGxvYyhzaXplb2YoKmhtbSksIEdGUF9LRVJORUwp OwogCWlmICghaG1tKQpAQCAtNzQsNTcgKzcyLDQ3IEBAIHN0YXRpYyBzdHJ1Y3QgaG1tICpobW1f Z2V0X29yX2NyZWF0ZShzdHJ1Y3QgbW1fc3RydWN0ICptbSkKIAlobW0tPm5vdGlmaWVycyA9IDA7 CiAJaG1tLT5kZWFkID0gZmFsc2U7CiAJaG1tLT5tbSA9IG1tOwotCW1tZ3JhYihobW0tPm1tKTsK IAotCXNwaW5fbG9jaygmbW0tPnBhZ2VfdGFibGVfbG9jayk7Ci0JaWYgKCFtbS0+aG1tKQotCQlt bS0+aG1tID0gaG1tOwotCWVsc2UKLQkJY2xlYW51cCA9IHRydWU7Ci0Jc3Bpbl91bmxvY2soJm1t LT5wYWdlX3RhYmxlX2xvY2spOworCWhtbS0+bW11X25vdGlmaWVyLm9wcyA9ICZobW1fbW11X25v dGlmaWVyX29wczsKKwlpZiAoX19tbXVfbm90aWZpZXJfcmVnaXN0ZXIoJmhtbS0+bW11X25vdGlm aWVyLCBtbSkpIHsKKwkJa2ZyZWUoaG1tKTsKKwkJcmV0dXJuIE5VTEw7CisJfQogCi0JaWYgKGNs ZWFudXApCi0JCWdvdG8gZXJyb3I7CisJbW1ncmFiKGhtbS0+bW0pOwogCiAJLyoKLQkgKiBXZSBz aG91bGQgb25seSBnZXQgaGVyZSBpZiBob2xkIHRoZSBtbWFwX3NlbSBpbiB3cml0ZSBtb2RlIGll IG9uCi0JICogcmVnaXN0cmF0aW9uIG9mIGZpcnN0IG1pcnJvciB0aHJvdWdoIGhtbV9taXJyb3Jf cmVnaXN0ZXIoKQorCSAqIFdlIGhvbGQgdGhlIGV4Y2x1c2l2ZSBtbWFwX3NlbSBoZXJlIHNvIHdl IGtub3cgdGhhdCBtbS0+aG1tIGlzCisJICogc3RpbGwgTlVMTCBvciAwIGtyZWYsIGFuZCBpcyBz YWZlIHRvIHVwZGF0ZS4KIAkgKi8KLQlobW0tPm1tdV9ub3RpZmllci5vcHMgPSAmaG1tX21tdV9u b3RpZmllcl9vcHM7Ci0JaWYgKF9fbW11X25vdGlmaWVyX3JlZ2lzdGVyKCZobW0tPm1tdV9ub3Rp ZmllciwgbW0pKQotCQlnb3RvIGVycm9yX21tOwotCi0JcmV0dXJuIGhtbTsKLQotZXJyb3JfbW06 CiAJc3Bpbl9sb2NrKCZtbS0+cGFnZV90YWJsZV9sb2NrKTsKLQlpZiAobW0tPmhtbSA9PSBobW0p Ci0JCW1tLT5obW0gPSBOVUxMOworCW1tLT5obW0gPSBobW07CiAJc3Bpbl91bmxvY2soJm1tLT5w YWdlX3RhYmxlX2xvY2spOwotZXJyb3I6Ci0JbW1kcm9wKGhtbS0+bW0pOwotCWtmcmVlKGhtbSk7 Ci0JcmV0dXJuIE5VTEw7CisJcmV0dXJuIGhtbTsKIH0KIAogc3RhdGljIHZvaWQgaG1tX2ZyZWVf cmN1KHN0cnVjdCByY3VfaGVhZCAqcmN1KQogewotCWtmcmVlKGNvbnRhaW5lcl9vZihyY3UsIHN0 cnVjdCBobW0sIHJjdSkpOworCXN0cnVjdCBobW0gKmhtbSA9IGNvbnRhaW5lcl9vZihyY3UsIHN0 cnVjdCBobW0sIHJjdSk7CisKKwkvKgorCSAqIFRoZSBtbS0+aG1tIHBvaW50ZXIgaXMga2VwdCB2 YWxpZCB3aGlsZSBub3RpZmllciBvcHMgY2FuIGJlIHJ1bm5pbmcKKwkgKiBzbyB0aGV5IGRvbid0 IGhhdmUgdG8gZGVhbCB3aXRoIGEgTlVMTCBtbS0+aG1tIHZhbHVlCisJICovCisJc3Bpbl9sb2Nr KCZobW0tPm1tLT5wYWdlX3RhYmxlX2xvY2spOworCWlmIChobW0tPm1tLT5obW0gPT0gaG1tKQor CQlobW0tPm1tLT5obW0gPSBOVUxMOworCXNwaW5fdW5sb2NrKCZobW0tPm1tLT5wYWdlX3RhYmxl X2xvY2spOworCW1tZHJvcChobW0tPm1tKTsKKworCWtmcmVlKGhtbSk7CiB9CiAKIHN0YXRpYyB2 b2lkIGhtbV9mcmVlKHN0cnVjdCBrcmVmICprcmVmKQogewogCXN0cnVjdCBobW0gKmhtbSA9IGNv bnRhaW5lcl9vZihrcmVmLCBzdHJ1Y3QgaG1tLCBrcmVmKTsKLQlzdHJ1Y3QgbW1fc3RydWN0ICpt bSA9IGhtbS0+bW07Ci0KLQltbXVfbm90aWZpZXJfdW5yZWdpc3Rlcl9ub19yZWxlYXNlKCZobW0t Pm1tdV9ub3RpZmllciwgbW0pOwogCi0Jc3Bpbl9sb2NrKCZtbS0+cGFnZV90YWJsZV9sb2NrKTsK LQlpZiAobW0tPmhtbSA9PSBobW0pCi0JCW1tLT5obW0gPSBOVUxMOwotCXNwaW5fdW5sb2NrKCZt bS0+cGFnZV90YWJsZV9sb2NrKTsKLQotCW1tZHJvcChobW0tPm1tKTsKKwltbXVfbm90aWZpZXJf dW5yZWdpc3Rlcl9ub19yZWxlYXNlKCZobW0tPm1tdV9ub3RpZmllciwgaG1tLT5tbSk7CiAJbW11 X25vdGlmaWVyX2NhbGxfc3JjdSgmaG1tLT5yY3UsIGhtbV9mcmVlX3JjdSk7CiB9CiAKLS0gCjIu MjEuMAoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJp LWRldmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBz Oi8vbGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVs 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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 0B88CC31E45 for ; Fri, 14 Jun 2019 00:45:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B653620850 for ; Fri, 14 Jun 2019 00:45:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="UA1C5NPq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B653620850 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E72E16B026A; Thu, 13 Jun 2019 20:44:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DAD5A6B026C; Thu, 13 Jun 2019 20:44:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B8D1D6B026F; Thu, 13 Jun 2019 20:44:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by kanga.kvack.org (Postfix) with ESMTP id 7022B6B026A for ; Thu, 13 Jun 2019 20:44:57 -0400 (EDT) Received: by mail-qk1-f197.google.com with SMTP id u129so642289qkd.12 for ; Thu, 13 Jun 2019 17:44:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:from:to:cc:subject:date :message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=iQFZUVD3bm8q29tG8rKodDV9niV08KJ4TO1srbmenK4=; b=E/taCVPq+f97Ed9wscAUpd/Fp1rtKG8wLsm9pmlinKogMM29vZThMs6EZjL5l2RR0r 7zM7m4eTJEQnCvugytFYHc2j2oaHvq1YUsmwtXHaXPtOzWygPGYBLtenywJ3vX18l0gH LBYH+G82FtpvVHmC5bm5axEXZO6jNEGV3qc+gj66BSd6UMkTFmSWkv0VmyBr2+L31s8h px8lC50IfxgF7d5hxIwmVcjaNZVeTdu/ZeUy6PR5j9M2ZbRQsE33T5jIMf61rYvSwZQX C10O77jj+Y9WMUYWQHv17LQcs3wqEdGgBPNd8ijByHLLTrhp7qZIZX1koLFD4bbjzGlI VZaQ== X-Gm-Message-State: APjAAAVLXF1Y49yTRCrHI6lMm7tR81GDK0mcZSo/CTRSaVoAo4spB3K/ 8yfNtTcni/Kyj6H6x2zzAB8UVhfqE0OSIivWYex+ngs9Rvfv2pVnoFmXNHzqvh+wInwuBsQ1QMo Kqyb9tcYT4vkQGs+jBx7vNEj5Wae8Ehf69rBFncSe03HAyOTaTX1+bRavpoiQfhYDMA== X-Received: by 2002:a37:de18:: with SMTP id h24mr18765496qkj.147.1560473097240; Thu, 13 Jun 2019 17:44:57 -0700 (PDT) X-Received: by 2002:a37:de18:: with SMTP id h24mr18765470qkj.147.1560473096612; Thu, 13 Jun 2019 17:44:56 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1560473096; cv=none; d=google.com; s=arc-20160816; b=z2vwekf0JYqv5CTw+lY+BO0tgfBvfKzvW0GXymUbvqvm/Gj9qi1ZKihUlW6oFeSyVw jKlcqtBI7fxAenVC4qLFBGa6NTR4yZfEDOrJj90xo2mbSg7agVS+485RdfcEBYSvMQw/ /3ALDdT+SB3TO25Lj5dKnW4BNgJT2Gu7VqV8OBO94cr0lWi5Osx6DTpcUnKjjRyGfzlJ 9vNl/8cYEKGvHv2xQb+ikpL8fPfdV1TnGBtgRPLfOYCIBsZsBJI7HPiRAhqvLZ5I5CMT fu0Kuj6ACe704BdyntI3IprUXLQ8tgciOHIPWqoO5paWiiB7ljhCMSPwrZIHyT704Krm qNQA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:dkim-signature; bh=iQFZUVD3bm8q29tG8rKodDV9niV08KJ4TO1srbmenK4=; b=eyOcvSGUvgcCpAFwsGZxuSuyiRiYhUlXs6OvgKLv5KuxAxc1npm/8jJGX3tjTaInwd DK3bNSDdhrv6WZAnYCtR+vtGszQzyOZSw2tEsQPWjjtJcoMKe1FFo4e+s3INyx26uj83 ttuvsYE8uEdqEzuCCnD/PIcc4rXekrvy9tz3EoeuqKBCt8DbMje9KNymtEDSEfG+2L2/ 2iV5AHA8hyxT7ETLHcKShuq3g/CbkC2NPRHL6oDcGFUKh41OPUod3vWeYHvMfjw9xBnZ VaS3HtsUfze9mcJI3Zhk0pCJn7wI8zwRleNnSLWu3RaSpEzeRso2wfCiCat7CkZRlOdS IK2g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@ziepe.ca header.s=google header.b=UA1C5NPq; spf=pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) smtp.mailfrom=jgg@ziepe.ca Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id o7sor1032381qvf.60.2019.06.13.17.44.56 for (Google Transport Security); Thu, 13 Jun 2019 17:44:56 -0700 (PDT) Received-SPF: pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@ziepe.ca header.s=google header.b=UA1C5NPq; spf=pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) smtp.mailfrom=jgg@ziepe.ca DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=iQFZUVD3bm8q29tG8rKodDV9niV08KJ4TO1srbmenK4=; b=UA1C5NPqvlm8z++G2laNCnwB/GWT7FWVDsQKpzNw396EnXD5grCbfeRcH4MVcv9Pxt Bw608pa0SQVwTZPesERpsVjDiheiUA0ZxpcaOhSCg3wFfLyCKPSY6m0rcqgkt0F7+Btu VcnvcuEPLZ4+31oNvXwgQ7Mzr5sdaFHqpO9DtB7bD2Mphja5lK5GoftxQttJJRITdM9l ZjsrOqKbZRdEDMQmdCny9EgekTtIr+yc7ps9gI2Z9j+YV7fGRjNJ2Dq2ZT34qRz8bx4L 2H+VNusPv5/abMz/Jh+ee/Y2I8OCp7Q6Wc38Z0vyw+mbGlfjmn34SHlMrcpzNY0sbebl RR8A== X-Google-Smtp-Source: APXvYqw56kQGKLPlj2Zgzkw2ysxgtbRlSboLCdNQH17EQruEZjbScaFJD3FwSz5lL9I3GIRJGcwbsg== X-Received: by 2002:a0c:afa2:: with SMTP id s31mr5894610qvc.186.1560473096316; Thu, 13 Jun 2019 17:44:56 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-156-34-55-100.dhcp-dynamic.fibreop.ns.bellaliant.net. [156.34.55.100]) by smtp.gmail.com with ESMTPSA id l3sm683628qkd.49.2019.06.13.17.44.54 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Jun 2019 17:44:54 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hbaKr-0005Jq-Ni; Thu, 13 Jun 2019 21:44:53 -0300 From: Jason Gunthorpe To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Cc: linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Jason Gunthorpe , Ira Weiny , Philip Yang Subject: [PATCH v3 hmm 04/12] mm/hmm: Simplify hmm_get_or_create and make it reliable Date: Thu, 13 Jun 2019 21:44:42 -0300 Message-Id: <20190614004450.20252-5-jgg@ziepe.ca> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190614004450.20252-1-jgg@ziepe.ca> References: <20190614004450.20252-1-jgg@ziepe.ca> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: From: Jason Gunthorpe As coded this function can false-fail in various racy situations. Make it reliable and simpler by running under the write side of the mmap_sem and avoiding the false-failing compare/exchange pattern. Due to the mmap_sem this no longer has to avoid racing with a 2nd parallel hmm_get_or_create(). Unfortunately this still has to use the page_table_lock as the non-sleeping lock protecting mm->hmm, since the contexts where we free the hmm are incompatible with mmap_sem. Signed-off-by: Jason Gunthorpe Reviewed-by: John Hubbard Reviewed-by: Ralph Campbell Reviewed-by: Ira Weiny Tested-by: Philip Yang --- v2: - Fix error unwind of mmgrab (Jerome) - Use hmm local instead of 2nd container_of (Jerome) v3: - Can't use mmap_sem in the SRCU callback, keep using the page_table_lock (Philip) --- mm/hmm.c | 84 ++++++++++++++++++++++++-------------------------------- 1 file changed, 36 insertions(+), 48 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 080b17a2e87e2d..4c64d4c32f4825 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -31,16 +31,6 @@ #if IS_ENABLED(CONFIG_HMM_MIRROR) static const struct mmu_notifier_ops hmm_mmu_notifier_ops; -static inline struct hmm *mm_get_hmm(struct mm_struct *mm) -{ - struct hmm *hmm = READ_ONCE(mm->hmm); - - if (hmm && kref_get_unless_zero(&hmm->kref)) - return hmm; - - return NULL; -} - /** * hmm_get_or_create - register HMM against an mm (HMM internal) * @@ -55,11 +45,19 @@ static inline struct hmm *mm_get_hmm(struct mm_struct *mm) */ static struct hmm *hmm_get_or_create(struct mm_struct *mm) { - struct hmm *hmm = mm_get_hmm(mm); - bool cleanup = false; + struct hmm *hmm; - if (hmm) - return hmm; + lockdep_assert_held_exclusive(&mm->mmap_sem); + + /* Abuse the page_table_lock to also protect mm->hmm. */ + spin_lock(&mm->page_table_lock); + if (mm->hmm) { + if (kref_get_unless_zero(&mm->hmm->kref)) { + spin_unlock(&mm->page_table_lock); + return mm->hmm; + } + } + spin_unlock(&mm->page_table_lock); hmm = kmalloc(sizeof(*hmm), GFP_KERNEL); if (!hmm) @@ -74,57 +72,47 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm) hmm->notifiers = 0; hmm->dead = false; hmm->mm = mm; - mmgrab(hmm->mm); - spin_lock(&mm->page_table_lock); - if (!mm->hmm) - mm->hmm = hmm; - else - cleanup = true; - spin_unlock(&mm->page_table_lock); + hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; + if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) { + kfree(hmm); + return NULL; + } - if (cleanup) - goto error; + mmgrab(hmm->mm); /* - * We should only get here if hold the mmap_sem in write mode ie on - * registration of first mirror through hmm_mirror_register() + * We hold the exclusive mmap_sem here so we know that mm->hmm is + * still NULL or 0 kref, and is safe to update. */ - hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; - if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) - goto error_mm; - - return hmm; - -error_mm: spin_lock(&mm->page_table_lock); - if (mm->hmm == hmm) - mm->hmm = NULL; + mm->hmm = hmm; spin_unlock(&mm->page_table_lock); -error: - mmdrop(hmm->mm); - kfree(hmm); - return NULL; + return hmm; } static void hmm_free_rcu(struct rcu_head *rcu) { - kfree(container_of(rcu, struct hmm, rcu)); + struct hmm *hmm = container_of(rcu, struct hmm, rcu); + + /* + * The mm->hmm pointer is kept valid while notifier ops can be running + * so they don't have to deal with a NULL mm->hmm value + */ + spin_lock(&hmm->mm->page_table_lock); + if (hmm->mm->hmm == hmm) + hmm->mm->hmm = NULL; + spin_unlock(&hmm->mm->page_table_lock); + mmdrop(hmm->mm); + + kfree(hmm); } static void hmm_free(struct kref *kref) { struct hmm *hmm = container_of(kref, struct hmm, kref); - struct mm_struct *mm = hmm->mm; - - mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); - spin_lock(&mm->page_table_lock); - if (mm->hmm == hmm) - mm->hmm = NULL; - spin_unlock(&mm->page_table_lock); - - mmdrop(hmm->mm); + mmu_notifier_unregister_no_release(&hmm->mmu_notifier, hmm->mm); mmu_notifier_call_srcu(&hmm->rcu, hmm_free_rcu); } -- 2.21.0