From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 017AA27816C for ; Wed, 1 Apr 2026 01:12:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775005974; cv=none; b=sG+q3DdNWWDlhkRMnKwGoRj0QUajYHYnDKz7aiDvKfzJjLH0phFL+aCaLul8FBiNU/pK83ir/9hDwn31xZxMuYekoFv8f6yT0GdFs2JAkujUqC99uPmrgvBufUEioVZtCRXedbQSehPWlrrZSoFwnc7lp+fHd8cSx+XX7IM7ujI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775005974; c=relaxed/simple; bh=476bPJH1yiHIKo35sskVy9NYL76Mta57CGMe4J6vEwM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LyGVQbz3GeApyk0Qi+djD7hwum5wzyBy0GgZg4LqvqdVXp49/YP8qeHH81OsrgIOw1wP/7soBIkX9JU7eCusDDWdaIhD8cjoxGMQz44YvHI3Bp5efU4skIjrEWV3zc8hrGlyv1aFDW1fSX9u4c83TY2xqQs2XKOTrrSq5YIWxoI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=SOQqRH/f; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SOQqRH/f" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775005972; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=X5u0Mvf0aIh7sPUU6rhICf017MOlqHpAj5kv9TV0zHM=; b=SOQqRH/fvQWGFbdhkgA3ZRMEPhoaPRWBmSSgCg16MCR0QgtAKIWuyQZhO5H83mgWf7xrNY IdsTJuyj56KWhuRZKEXTvfkfLWRNfrtuJBw0DZHqKQt2R4p+07GKRgpWiirP5LkVKB7yN1 p1Y6y5O+37l8y2vO0mTCJOUsrBgAPEY= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-486-FHqy26LoMYmKoZ1mlFpj7w-1; Tue, 31 Mar 2026 21:12:48 -0400 X-MC-Unique: FHqy26LoMYmKoZ1mlFpj7w-1 X-Mimecast-MFC-AGG-ID: FHqy26LoMYmKoZ1mlFpj7w_1775005967 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 31DE21800344; Wed, 1 Apr 2026 01:12:47 +0000 (UTC) Received: from fedora (unknown [10.72.116.96]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B700130001A2; Wed, 1 Apr 2026 01:12:43 +0000 (UTC) Date: Wed, 1 Apr 2026 09:12:38 +0800 From: Ming Lei To: Bart Van Assche Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Damien Le Moal Subject: Re: [PATCH v3 4/6] block: Reduce the minimum value for the maximum DMA segment size Message-ID: References: <20260327211349.2239633-1-bvanassche@acm.org> <20260327211349.2239633-5-bvanassche@acm.org> <7fe454fa-d39b-4d2f-a238-297df2261cdd@acm.org> <70b6d783-fdd3-4dce-807a-80b0967906a3@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: <70b6d783-fdd3-4dce-807a-80b0967906a3@acm.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Tue, Mar 31, 2026 at 09:12:54AM -0700, Bart Van Assche wrote: > On 3/30/26 5:57 PM, Ming Lei wrote: > > What is the exactly code path you are trying to cover by changing > > BLK_MIN_SEGMENT_SIZE? > > In the solution I came up with and that we are no longer using in Android > (we switched to the upstream approach) there were code paths > that are only triggered if max_segment_size < PAGE_SIZE (see also > https://lore.kernel.org/linux-block/20230522222554.525229-1-bvanassche@acm.org/). > I'm not sure there are any such code paths left? Then please setup one aarch64 VM with 16/64K PAGE_SIZE for covering the code path. It is insane to reduce BLK_MIN_SEGMENT_SIZE just for faking max_segment_size < PAGE_SIZE in 4K page size kernel for test purpose only, IMO. Thanks, Ming