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Thu, 23 Apr 2020 21:07:53 -0700 (PDT) Received: from N-20L6PF1KTYA2 ([131.228.2.21]) by smtp.gmail.com with ESMTPSA id w21sm3365383lji.26.2020.04.23.21.07.51 (version=TLS1_2 cipher=AES128-GCM-SHA256 bits=128/128); Thu, 23 Apr 2020 21:07:52 -0700 (PDT) Date: Fri, 24 Apr 2020 12:07:50 +0800 From: "Li Xinhai" To: "Jason Gunthorpe" , "Mike Kravetz" Cc: "linux-mm@kvack.org" , akpm , "Punit Agrawal" , Longpeng Subject: Re: [PATCH] mm/hugetlb: avoid unnecessary check on pud and pmd entry in huge_pte_offset References: <1587646154-26276-1-git-send-email-lixinhai.lxh@gmail.com>, , <20200423183835.GA13640@mellanox.com> X-Priority: 3 X-GUID: 428DEC0B-64EC-454A-ADC5-5EFB1EDDF54B X-Has-Attach: no X-Mailer: Foxmail 7.2.13.365[cn] Mime-Version: 1.0 Message-ID: <202004241207494655904@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 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: T24gMjAyMC0wNC0yNMKgYXQgMDI6MzjCoEphc29uIEd1bnRob3JwZcKgd3JvdGU6Cj5PbiBUaHUs IEFwciAyMywgMjAyMCBhdCAxMToxNDoyOEFNIC0wNzAwLCBNaWtlIEtyYXZldHogd3JvdGU6Cj4+ IENjIGEgZmV3IHBlb3BsZSB3aG8gaGF2ZSBsb29rZWQgYXQgaHVnZV9wdGVfb2Zmc2V0KCkgcmVj ZW50bHkuCj4+Cj4+IE9uIDQvMjMvMjAgNTo0OSBBTSwgTGkgWGluaGFpIHdyb3RlOgo+PiA+IFdo ZW4gaHVnZV9wdGVfb2Zmc2V0KCkgaXMgY2FsbGVkLCB0aGUgcGFyYW1ldGVyIHN6IGNhbiBvbmx5 IGJlIFBVRF9TSVpFCj4+ID4gb3IgUE1EX1NJWkUuCj4+ID4gSWYgc3ogaXMgUFVEX1NJWkUgYW5k IGNvZGUgY2FuIHJlYWNoIHB1ZCwgdGhlbiAqcHVkIG11c3QgYmUgbm9uZSwgb3IKPj4gPiBub3Jt YWwgaHVnZXRsYiBlbnRyeSwgb3Igbm9uLXByZXNlbnQgKG1pZ3JhdGlvbiBvciBod3BvaXNvbmVk KSBodWdldGxiCj4+ID4gZW50cnksIGFuZCB3ZSBjYW4gZGlyZWN0bHkgcmV0dXJuIHB1ZC4KPj4g PiBXaGVuIHN6IGlzIFBNRF9TSVpFLCBwdWQgbXVzdCBiZSBub25lIG9yIHByZXNlbnQsIGFuZCBp ZiBjb2RlIGNhbiByZWFjaAo+PiA+IHBtZCwgd2UgY2FuIGRpcmVjdGx5IHJldHVybiBwbWQuCj4+ ID4KPj4gPiBTbywgYWZ0ZXIgdGhpcyBwYXRjaCwgdGhlIGNvZGUgaXMgc2ltcGxpZmllZCBieSBm aXJzdCBjaGVjayBvbiB0aGUKPj4gPiBwYXJhbWV0ZXIgc3osIGFuZCBhdm9pZCB1bm5lY2Vzc2Fy eSBjaGVja3MgaW4gY3VycmVudCBjb2RlLgo+PiA+Cj4+ID4gU2lnbmVkLW9mZi1ieTogTGkgWGlu aGFpIDxsaXhpbmhhaS5seGhAZ21haWwuY29tPgo+PiA+IENjOiBNaWtlIEtyYXZldHogPG1pa2Uu a3JhdmV0ekBvcmFjbGUuY29tPgo+PiA+IENjOiBBbmRyZXcgTW9ydG9uIDxha3BtQGxpbnV4LWZv dW5kYXRpb24ub3JnPgo+PiA+wqAgbW0vaHVnZXRsYi5jIHwgMjQgKysrKysrKysrLS0tLS0tLS0t LS0tLS0tCj4+ID7CoCAxIGZpbGUgY2hhbmdlZCwgOSBpbnNlcnRpb25zKCspLCAxNSBkZWxldGlv bnMoLSkKPj4gPgo+PiA+IGRpZmYgLS1naXQgYS9tbS9odWdldGxiLmMgYi9tbS9odWdldGxiLmMK Pj4gPiBpbmRleCBiY2FiYmUwLi5lMTQyNGY1IDEwMDY0NAo+PiA+ICsrKyBiL21tL2h1Z2V0bGIu Ywo+PiA+IEBAIC01MzY1LDggKzUzNjUsOCBAQCBwdGVfdCAqaHVnZV9wdGVfb2Zmc2V0KHN0cnVj dCBtbV9zdHJ1Y3QgKm1tLAo+PiA+wqAgewo+PiA+wqAgcGdkX3QgKnBnZDsKPj4gPsKgIHA0ZF90 ICpwNGQ7Cj4+ID4gLQlwdWRfdCAqcHVkLCBwdWRfZW50cnk7Cj4+ID4gLQlwbWRfdCAqcG1kLCBw bWRfZW50cnk7Cj4+ID4gKwlwdWRfdCAqcHVkOwo+PiA+ICsJcG1kX3QgKnBtZDsKPj4gPsKgCj4+ ID7CoCBwZ2QgPSBwZ2Rfb2Zmc2V0KG1tLCBhZGRyKTsKPj4gPsKgIGlmICghcGdkX3ByZXNlbnQo KnBnZCkpCj4+ID4gQEAgLTUzNzYsMjIgKzUzNzYsMTYgQEAgcHRlX3QgKmh1Z2VfcHRlX29mZnNl dChzdHJ1Y3QgbW1fc3RydWN0ICptbSwKPj4gPsKgIHJldHVybiBOVUxMOwo+PiA+wqAKPj4gPsKg IHB1ZCA9IHB1ZF9vZmZzZXQocDRkLCBhZGRyKTsKPj4gPiAtCXB1ZF9lbnRyeSA9IFJFQURfT05D RSgqcHVkKTsKPj4gPiAtCWlmIChzeiAhPSBQVURfU0laRSAmJiBwdWRfbm9uZShwdWRfZW50cnkp KQo+PiA+IC0JcmV0dXJuIE5VTEw7Cj4+ID4gLQkvKiBodWdlcGFnZSBvciBzd2FwPyAqLwo+PiA+ IC0JaWYgKHB1ZF9odWdlKHB1ZF9lbnRyeSkgfHwgIXB1ZF9wcmVzZW50KHB1ZF9lbnRyeSkpCj4+ ID4gKwlpZiAoc3ogPT0gUFVEX1NJWkUpCj4+ID4gKwkvKiBtdXN0IGJlIHB1ZF9odWdlIG9yIHB1 ZF9ub25lICovCj4+ID7CoCByZXR1cm4gKHB0ZV90ICopcHVkOwo+PiA+IC0KPj4gPiAtCXBtZCA9 IHBtZF9vZmZzZXQocHVkLCBhZGRyKTsKPj4gPiAtCXBtZF9lbnRyeSA9IFJFQURfT05DRSgqcG1k KTsKPj4gPiAtCWlmIChzeiAhPSBQTURfU0laRSAmJiBwbWRfbm9uZShwbWRfZW50cnkpKQo+PiA+ ICsJaWYgKCFwdWRfcHJlc2VudCgqcHVkKSkKPj4gPsKgIHJldHVybiBOVUxMOwo+PiA+IC0JLyog aHVnZXBhZ2Ugb3Igc3dhcD8gKi8KPj4gPiAtCWlmIChwbWRfaHVnZShwbWRfZW50cnkpIHx8ICFw bWRfcHJlc2VudChwbWRfZW50cnkpKQo+PiA+IC0JcmV0dXJuIChwdGVfdCAqKXBtZDsKPj4gPiAr CS8qIG11c3QgaGF2ZSBhIHZhbGlkIGVudHJ5IGFuZCBzaXplIHRvIGdvIGZ1cnRoZXIgKi8KPj4g PsKgCj4+ID4gLQlyZXR1cm4gTlVMTDsKPj4gPiArCXBtZCA9IHBtZF9vZmZzZXQocHVkLCBhZGRy KTsKPj4KPj4gQ2FuIHdlIGdldCBoZXJlIHdpdGggc3ogPSBQTURfU0laRSBhbmQgcHVkX25vbmUo KnB1ZCk/wqAgV291bGQgdGhhdCBiZQo+PiBhbiBpc3N1ZSBmb3IgdGhlIHBtZF9vZmZzZXQoKSBj YWxsPwo+Cj5DZXJ0YWlubHkgcG1kX29mZnNldCgpIG11c3Qgb25seSBiZSBjYWxsZWQgaWYgdGhl IFBVRCBlbnRyeSBpcwo+cG9pbnRpbmcgYXQgYSBwbWQgbGV2ZWwuCj4KPkFGQUlLIHRoaXMgbWVh bnMgaXQgc2hvdWxkIG5vdCBiZSBjYWxsZWQgb24gcHVkX25vbmUoKSwgcHVkX2h1Z2UoKSBvcgo+ IXB1ZF9wcmVzZW50KCkgY2FzZXMuIAoKVGhlIHRlc3Qgb2bCoCFwdWRfcHJlc2VudCgqcHVkKSBh bHNvIGJsb2NrIHB1ZF9ub25lKCpwdWQpLCBzbyB3aGVuIHN6ID09ClBNRF9TSVpFLCBwbWRfb2Zm c2V0KCkgb25seSBjYWxsZWQgd2l0aCBhIHZhbGlkIFBVRCBlbnRyeSB3aGljaCBwb2ludCB0byBQ TUQKcGFnZSB0YWJsZS4KCj4KPkphc29u