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[209.85.208.48]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b65eb525dffsm1083309266b.61.2025.10.21.08.50.37 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Oct 2025 08:50:37 -0700 (PDT) Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-63c31c20b64so7312124a12.1 for ; Tue, 21 Oct 2025 08:50:37 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCWioPYG0UcoESpL/3quhwb+2PWbjx/6ltAkkBWxgPi1Uk5EfznY/RN9C4Gq1CaoZezuDqdGgd7pRg==@kvack.org X-Received: by 2002:a05:6402:3554:b0:63c:4d42:993d with SMTP id 4fb4d7f45d1cf-63c4d429b92mr11883163a12.31.1761061836721; Tue, 21 Oct 2025 08:50:36 -0700 (PDT) MIME-Version: 1.0 References: <20251017141536.577466-1-kirill@shutemov.name> <20251019215328.3b529dc78222787226bd4ffe@linux-foundation.org> <44ubh4cybuwsb4b6na3m4h3yrjbweiso5pafzgf57a4wgzd235@pgl54elpqgxa> In-Reply-To: <44ubh4cybuwsb4b6na3m4h3yrjbweiso5pafzgf57a4wgzd235@pgl54elpqgxa> From: Linus Torvalds Date: Tue, 21 Oct 2025 05:50:19 -1000 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWBOp9VJpCXyIKnJNta0lggyjzqPvsPMHPbiYL935bxgvLcEoC8FIS9Zxss Message-ID: Subject: Re: [PATCH] mm/filemap: Implement fast short reads To: Kiryl Shutsemau Cc: 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: 78BAD40012 X-Rspamd-Server: rspam02 X-Stat-Signature: 1bm9b1enxdyzt18pt7b18aahhwqkyezd X-HE-Tag: 1761061839-449327 X-HE-Meta: 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 qbIMSf4j BwRrC1yg1iv0kmgiUszsZ36HlgN6cspMBmxQj27HKSkL2V73d3sC+N3rJYWNuph4+6bSh6pzz9LrQl2QIfxgOg863wsyXOpQJkQfOiM4fvsjcKokbsbQjuFGAc6nc+5kxdVWP3nPfQV3cleSxwCO/C2mH3+3RbfqASbxnKxxMRIA1J9Q+0uYzW8va/A== 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, 20 Oct 2025 at 01:33, Kiryl Shutsemau wrote: > > On Sun, Oct 19, 2025 at 09:53:28PM -0700, Andrew Morton wrote: > > > > A use case for alloca() or equiv. That would improve the average-case > > stack depth but not the worst-case. > > __kstack_alloca()/__builtin_alloca() would work and it bypassed > -Wframe-larger-than warning. > > But I don't see any real users. Yes, and we've walked away from alloca() (and on-stack VLAs, which are really exactly the same thing as far as a compiler is concerned), because it makes static analysis much *MUCH* harder. Let's not ever re-introduce dynamic stack use in the kernel. Linus