From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CCF5E1E7C3B; Thu, 20 Mar 2025 16:44:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742489101; cv=none; b=sv3v01HPaln7PRzc9op6X2+HdVXqbRqb4kwKSHhIyZnuhLr9WXRgzyu/5LJ4hn52J6Zu3ArYR0CfYgA+roP7yFGvzvoQb4gLKkdp++zuSACqcTCb9171Z7xqbFK+PHPwzBtbBNnAyThfnNU2C0OigNt5qhnbmcnmTLH4dphrwbA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742489101; c=relaxed/simple; bh=/u61Jwp+ai5pZlaKMnn+SZJFHL2VxcANp7aVTHQUCEQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hlzHC+YGefjJntQTG/PPr3qV6JI3PGt1h2GK+CXM7itK7sXk1LDWAIyJsbAZtUd1dNqeZpu8ZjFXwHybbD6QkNoyG8r4wncphfFC27TmiYDK61fwH31pNgd0yDT3I7idsztoziDkV6qfEo+jUqKSNvAgNTw16kAJj13s/rk3u2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 271EE68AA6; Thu, 20 Mar 2025 17:44:52 +0100 (CET) Date: Thu, 20 Mar 2025 17:44:51 +0100 From: Christoph Hellwig To: Bart Van Assche Cc: Matthew Wilcox , Luis Chamberlain , leon@kernel.org, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@kernel.dk, joro@8bytes.org, brauner@kernel.org, hare@suse.de, david@fromorbit.com, djwong@kernel.org, john.g.garry@oracle.com, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, kernel@pankajraghav.com Subject: Re: [RFC 2/4] blkdev: lift BLK_MAX_BLOCK_SIZE to page cache limit Message-ID: <20250320164451.GA21364@lst.de> References: <20250320111328.2841690-1-mcgrof@kernel.org> <20250320111328.2841690-3-mcgrof@kernel.org> <5459e3e0-656c-4d94-82c7-3880608f9ac8@acm.org> <7cc6f537-aac4-4bfc-80f0-1829a850d56a@acm.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7cc6f537-aac4-4bfc-80f0-1829a850d56a@acm.org> User-Agent: Mutt/1.5.17 (2007-11-01) On Thu, Mar 20, 2025 at 09:34:50AM -0700, Bart Van Assche wrote: > The fact that this change is proposed because there are device > manufacturers that want to produce devices with block sizes larger than > 64 KiB would be useful information for the commit message. I think it's just the proposal that is very confused. Keith pointed out that number of segments mostly matters when you have 4k non-contiguous pages and that's where the quoted limit comes from. The LBA size is a lower bound to the folio size in the page cache, so the limit automatically increases with that, although in practice the file system will usually allocate larger folios even with a smaller block size, and I assume most systems (or at least the ones that care about performance) actually use transparent huge pages/folios for anonymous memory as well.