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[209.85.208.48]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b65eb036b2bsm300367166b.49.2025.10.18.10.57.06 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Oct 2025 10:57:06 -0700 (PDT) Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-63c0c9a408aso5261316a12.3 for ; Sat, 18 Oct 2025 10:57:06 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVxD9Nw132ZHGUzxN/8nrwSD4bRzh2r5HaXEtKzywzTFhmIcxJqB7WsjVQeBsH+PX+wBxmoE2moGQ==@kvack.org X-Received: by 2002:a05:6402:524c:b0:639:1ee3:4e83 with SMTP id 4fb4d7f45d1cf-63c1f64f094mr7116093a12.8.1760810225989; Sat, 18 Oct 2025 10:57:05 -0700 (PDT) MIME-Version: 1.0 References: <20251017141536.577466-1-kirill@shutemov.name> In-Reply-To: <20251017141536.577466-1-kirill@shutemov.name> From: Linus Torvalds Date: Sat, 18 Oct 2025 07:56:48 -1000 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWBhMhgs4_s15aKV87bAatc3jK6By6Ho8BjAuIc9dhonJUNbnDV1fLJr0qc 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, Kiryl Shutsemau Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 32ABF100005 X-Stat-Signature: aae89atxjic39iu9e9trcduz65mj8kuz X-Rspam-User: X-HE-Tag: 1760810228-396101 X-HE-Meta: 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 q60xPOJJ 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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 Fri, 17 Oct 2025 at 04:15, Kiryl Shutsemau wrote: > > To address this issue, introduce i_pages_delete_seqcnt, which increments > each time a folio is deleted from the page cache and implement a modified > page cache lookup protocol for short reads: So this patch looks good to me, but to avoid the stack size warnings, let's just make FAST_READ_BUF_SIZE be 768 bytes or something like that, not the full 1k. It really shouldn't make much of a difference, and we do have that stack size limit check for a reason. And obviously > --- a/fs/inode.c > +++ b/fs/inode.c > + seqcount_spinlock_init(&mapping->i_pages_delete_seqcnt, > + &mapping->i_pages->xa_lock); will need to use '&mapping->i_pages.xa_lock', since mapping->i_pages is the embedded xarray, not a pointer to it. But I do think the patch looks quite good. Linus