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[209.85.218.48]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b4865a83f4esm1202484166b.30.2025.10.06.11.15.08 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Oct 2025 11:15:08 -0700 (PDT) Received: by mail-ej1-f48.google.com with SMTP id a640c23a62f3a-b3d5088259eso770227566b.1 for ; Mon, 06 Oct 2025 11:15:08 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCWMOMM68bAh2aoEye675gqbho3g6mMGzpwngRo07Q3TOrYBZQcIrvwjgem7JqmvHoMKhWZYtZjDFA==@kvack.org X-Received: by 2002:a17:907:97c8:b0:b3f:b7ca:26c5 with SMTP id a640c23a62f3a-b49c44b0c80mr1722317966b.59.1759774507739; Mon, 06 Oct 2025 11:15:07 -0700 (PDT) MIME-Version: 1.0 References: <4bjh23pk56gtnhutt4i46magq74zx3nlkuo4ym2tkn54rv4gjl@rhxb6t6ncewp> <5zq4qlllkr7zlif3dohwuraa7rukykkuu6khifumnwoltcijfc@po27djfyqbka> In-Reply-To: <5zq4qlllkr7zlif3dohwuraa7rukykkuu6khifumnwoltcijfc@po27djfyqbka> From: Linus Torvalds Date: Mon, 6 Oct 2025 11:14:51 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWBukV_xtmU11JJsDRqxO_VMhKc_Ul7jDhpyeBLq29Yx3q9wMoG-6X-gkno Message-ID: Subject: Re: Optimizing small reads To: Kiryl Shutsemau Cc: Matthew Wilcox , Luis Chamberlain , Linux-MM , linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 2849C180009 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: w9k37r9sz9bzoiuxsrhgwymy49sopj9j X-HE-Tag: 1759774510-47404 X-HE-Meta: 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 OOVtzG9B 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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 Mon, 6 Oct 2025 at 11:04, Kiryl Shutsemau wrote: > > > > So I think you can just change the seqcount_spinlock_t to a plain > > seqcount_t with no locking at all, and document that external locking. > > That is not a spinlock. It is lockdep annotation that we expect this > spinlock to be held there for seqcount write to be valid. > > It is NOP with lockdep disabled. Ahh, right you are. Complaint withdrawn. I had the "lockref" kind of thing in mind, but yes, the seqcount thing already have an external lock model. Linus