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Fri, 24 Apr 2020 07:07:23 -0700 (PDT) Received: from N-20L6PF1KTYA2 ([131.228.2.20]) by smtp.gmail.com with ESMTPSA id c2sm4525663ljk.97.2020.04.24.07.07.20 (version=TLS1_2 cipher=AES128-GCM-SHA256 bits=128/128); Fri, 24 Apr 2020 07:07:21 -0700 (PDT) Date: Fri, 24 Apr 2020 22:07:19 +0800 From: "Li Xinhai" To: "Jason Gunthorpe" Cc: "Mike Kravetz" , "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>, <202004241207494655904@gmail.com>, <20200424125753.GK13640@mellanox.com>, <2020042421333861801820@gmail.com>, <20200424134206.GM13640@mellanox.com> X-Priority: 3 X-GUID: CED2EAAE-1604-49F3-A45C-021C1B6141F5 X-Has-Attach: no X-Mailer: Foxmail 7.2.13.365[cn] Mime-Version: 1.0 Message-ID: <2020042422071809487733@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: T24gMjAyMC0wNC0yNMKgYXQgMjE6NDLCoEphc29uIEd1bnRob3JwZcKgd3JvdGU6Cj5PbiBGcmks IEFwciAyNCwgMjAyMCBhdCAwOTozMzo0MFBNICswODAwLCBMaSBYaW5oYWkgd3JvdGU6Cj4+ID4K Pj4gPj4gLCBzbyB3aGVuIHN6ID09IFBNRF9TSVpFLCBwbWRfb2Zmc2V0KCkgb25seSBjYWxsZWQg d2l0aCBhIHZhbGlkIFBVRAo+PiA+PiBlbnRyeSB3aGljaCBwb2ludCB0byBQTUQgcGFnZSB0YWJs ZS4KPj4gPgo+PiA+QnV0IHdoYXQgcHJldmVudHMgcHVkX2h1Z2U/Cj4+ID4KPj4gaWYgc3ogPT0g UFVEX1NJWkUsIHRoZSAncmV0dXJuIChwdGVfdCopcHVkJyBhbHJhZHkgZW5kIHRoZSBmdW5jdGlv biwgd2hpY2ggY292ZXIKPj4gcHVkX2h1Z2UoKSBhbmQgcHVkX25vbmUoKSwgYmVjYXVzZSB3ZSB0 aGUgbWFwcGluZyBpcyBmb3IgUFVEX1NJWkUgaHVnZSBwYWdlLgo+Pgo+PiBTbywgdGhlcmUgaXMg bm8gcG9zc2liaWxpdHkgZm9yIHBtZF9vZmZzZXQoKSBiZWVuIGNhbGxlZCB3aXRoIGludmFsaWQg cHVkIGVudHJ5Lgo+PiBCZWxvdyBpcyB0aGUgY29kZSBJIHVzZWQgZm9yIHRlc3Qgd2hpY2ggaGFz IEJVR19PTiwgdGhhdCBzaG91bGQgZ2l2ZSBtb3JlCj4+IGNsZWFyIGlkZWEgYWJvdXQgdGhlIHNl bWFudGljcyBvZiBjb2RlIHBhdGg6Cj4+Cj4+IC4uLgo+PiBwdWQgPSBwdWRfb2Zmc2V0KHA0ZCwg YWRkcik7Cj4+IGlmIChzeiA9PSBQVURfU0laRSkgewo+PiAvKiBtdXN0IGJlIHB1ZF9odWdlIG9y IHB1ZF9ub25lICovCj4+IEJVR19PTighcHVkX2h1Z2UoKnB1ZCkgJiYgIXB1ZF9ub25lKCpwdWQp KTsKPj4gcmV0dXJuIChwdGVfdCAqKXB1ZDsgLy8gbm90ZSB0aGF0IHJldHVybiB2YWxpZCBwb2lu dGVyIGZvciBwdWRfbm9uZSgpIGNhc2UsCj4+IC8vIGluc3RlYWQgb2YgTlVMTCwgdGhhdCBpcyBz YW1lIHNlbWFudGljcyBhcyBleGlzdGluZyBjb2RlLgo+PiB9Cj4+IGlmICghcHVkX3ByZXNlbnQo KnB1ZCkpCj4+IHJldHVybiBOVUxMOyAvLyBub3RlIHRoYXQgb25seSByZXR1cm4gTlVMTCBpbiBj YXNlIHB1ZCBub3QgcHJlc2VudCwKPj4gLy8gc2FtZSBzZW1hdGljcyBhcyBleGlzdGluZyBjb2Rl Lgo+PiAvKiBtdXN0IGhhdmUgYSB2YWxpZCBlbnRyeSBhbmQgc2l6ZSB0byBnbyBmdXJ0aGVyICov Cj4+IEJVR19PTihzeiAhPSBQTURfU0laRSk7Cj4+Cj4+IHBtZCA9IHBtZF9vZmZzZXQocHVkLCBh ZGRyKTsKPj4gLyogbXVzdCBiZSBwbWRfaHVnZSBvciBwbWRfbm9uZSAqLwo+PiBCVUdfT04oIXBt ZF9odWdlKCpwbWQpICYmICFwbWRfbm9uZSgqcG1kKSk7Cj4KPkJ1dCB3aHkgaXMgIXBtZF9odWdl KCkgPyBUaGUgcHJpb3IgY29kZSByZXR1cm5lZCBudWxsIGhlcmUsIGlzIHRoYXQKPmRlYWQgY29k ZT8gWW91ciBjb21taXQgbWVzc2FnZSBzaG91bGQgZXhwbGFpbiBhbGwgb2YgdGhpcy4uCj4gCmxl dCdzIHNlZSBleGlzaW5nIGNvZGUgZm9yIHBtZCBwYXJ0LCB0aGUgcmVhc29uIGFyZSBpbiBjb21t ZW50czoKLi4uCsKgIMKgIMKgIMKgIHBtZCA9IHBtZF9vZmZzZXQocHVkLCBhZGRyKTsKwqAgwqAg wqAgwqAgaWYgKHN6ICE9IFBNRF9TSVpFICYmIHBtZF9ub25lKCpwbWQpKQrCoCDCoCDCoCDCoCDC oCDCoCDCoCDCoCByZXR1cm4gTlVMTDsgLy8gZGVhZCBjb2RlLCBtdXN0IHN6ID09IFBNRF9TSVpF CsKgIMKgIMKgIMKgIC8qIGh1Z2VwYWdlIG9yIHN3YXA/ICovCsKgIMKgIMKgIMKgIGlmIChwbWRf aHVnZSgqcG1kKSB8fCAhcG1kX3ByZXNlbnQoKnBtZCkpIC8vICFwbWRfcHJlc2VudCgpIGFsc28g Y292ZXIgcG1kX25vbmUoKSwKwqAgwqAgwqAgwqAgwqAgwqAgwqAgwqAgcmV0dXJuIChwdGVfdCAq KXBtZDsgLy8gc28sIGFsbCBwb3NzaWJsZSBhbmQgdmFsaWQgdmFsdWUgaW4gcG1kIGVudHJ5IHdp bGwgcmVhY2ggaGVyZS4KCglyZXR1cm4gTlVMTDsgLy8gZGVhZCBjb2RlOyBjYW4gd2UgaGF2ZSAo IXBtZF9odWdlKCkgJiYgcG1kX3ByZXNlbnQoKSkgYW5kIHJlYWNoIGhlcmU/wqAKCQkvLyBubywg YmVjYXVzZSB0aGlzIGlzIGEgaHVnZXRsYiBtYXBwaW5nLiBvdGhlcndpc2UsIHRoZXJlIGlzIGlu dmFsaWQgdmFsdWUgaW4gcG1kIGVudHJ5LgouLi4KCj5KYXNvbg==