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[209.85.208.41]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-63c48acf60dsm10835174a12.18.2025.10.21.21.25.46 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Oct 2025 21:25:46 -0700 (PDT) Received: by mail-ed1-f41.google.com with SMTP id 4fb4d7f45d1cf-63d6ee383bdso3725378a12.2 for ; Tue, 21 Oct 2025 21:25:46 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVrPH6tJKl3zj8TkmfqJ2csvTOBCUwCHpQxFt+qUq3GtoPSYCcetMF96fdo8JImQLs+Ag2Be9snJw==@kvack.org X-Received: by 2002:a05:6402:2113:b0:63b:f91e:60a2 with SMTP id 4fb4d7f45d1cf-63c1f6c1fc8mr18494752a12.25.1761107146449; Tue, 21 Oct 2025 21:25:46 -0700 (PDT) MIME-Version: 1.0 References: <20251017141536.577466-1-kirill@shutemov.name> <20251019215328.3b529dc78222787226bd4ffe@linux-foundation.org> <44ubh4cybuwsb4b6na3m4h3yrjbweiso5pafzgf57a4wgzd235@pgl54elpqgxa> In-Reply-To: From: Linus Torvalds Date: Tue, 21 Oct 2025 18:25:30 -1000 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWB9CwG0IBKbkuN6M06jeHmD1GxcMpSycRZvl1CF5oywYvt7kYLWS-f-Gn8 Message-ID: Subject: Re: [PATCH] mm/filemap: Implement fast short reads To: Dave Chinner Cc: Kiryl Shutsemau , Andrew Morton , David Hildenbrand , Matthew Wilcox , Alexander Viro , Christian Brauner , Jan Kara , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Suren Baghdasaryan Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: 722DC4000F X-Rspamd-Server: rspam03 X-Stat-Signature: zw67gbyscrjspdu1op4q4wskz99zp95u X-HE-Tag: 1761107150-465745 X-HE-Meta: U2FsdGVkX18fC19mdHqnerGOK52aZ49aIrDXWx75o9FwKzH6tj6TtmXfxz566g733phQlxKFeO55UfU9zinXPPIDgXz0h422KnAd2BaTYEneCHvkXXd5dHRjd6oadW5wto8ldIcxjoT4zVdgvEztdvZwwkzlz25NDXnwEDJsgwgY8CmxJCmVYzBaDYcTI+eewSMCIEkBsnoqqVIZKnyI0YDTYh7o9fSFAArWOyboMbe15o2nRAEK/BtV69mMZ0XduY2O/WAvAD8AiNQTYOvxuejf6+VqHJlW3Uxr2QWvBFwX8DtA9SzDvBSPSd7iOtJYgwwnLay5mUpWFM+VoIF6c07ZlJKAmyjEhS8RvFea7IAbKq4F6BDUP8DgQfS9l2dlKMvKjAA8L1e5qP2mPPHKqazdIw0qqAl2Xp5pqYloTSOCHPY1UDhNQ6JsT/ofnNa6xRNHA5crlKMVnn8cGqvPk/cwfDq05Qa9Dj3IkTKSZvRR/WfjP0Up6YgTXw4pTPQUM6aRD9AEKPoCi6kzlooDmI9RGExJA9MEOBRqh5lG9XcPx9JRjBKGSTwvag8THjTBtnpuJz9dsLUUU543C22O8pvXbua5x5HjAIwGq12riTDwyUf8Sey6xNL2q3pmr9PGJr8BKyqOOExREgmp0H/sQMYxXobmh4WSDMI1Veoo4zWf6bXshIrCTdP87etkWi4wKo/uxpfnUZdqeowt6aRsxsbfMCLLsU1WB4sl5lnuvxKqbbzPIKtqdHhuVfDzOj0YNxT5ZcF7IZEsF5jRjcfXp5ziZES1GGbsTsJio1zHSrMeBEzt0gkFhcjU4rHb7OQqwZhtkRTFBN7xNAZkFrH7W/m6C3CYRB/pzxy5vNpnuYXikj88C+vBEhWAQDgG5PGMaUQ/KR3+ffrZa78puij5oS4OCoOHct6FNI3sJrbU9wcXNBS9j7Mks+hiiVnexnwQ3eV4H/rJ9Oa5xNCldFT vC52cxxe 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 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: List-Subscribe: List-Unsubscribe: On Tue, 21 Oct 2025 at 13:39, Dave Chinner wrote: > > > > > 1. Locate a folio in XArray. > > > > 2. Obtain a reference on the folio using folio_try_get(). > > > > 3. If successful, verify that the folio still belongs to > > > > the mapping and has not been truncated or reclaimed. > > What about if it has been hole-punched? The sequence number check should take care of anything like that. Do you have any reason to believe it doesn't? Yes, you can get the "before or after or between" behavior, but you can get that with perfectly regular reads that take the refcount on the page. Reads have never taken the page lock, and have never been serialized that way. So the fast case changes absolutely nothing in this respect that I can see. Linus