From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1C00B3446C2; Wed, 19 Nov 2025 09:55:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763546123; cv=none; b=Amz0jYJE/Fwag7sePY24qTfC0/c5OU9bBmA6abSlSLrFnwRlPEm+QlIFx86dhVzWxJsws2yNAW+p/l/3XoIphxCGtEjcrTT997Q0vowqUOPNFLow8JCliw9wRG41Y4p+S9SMS+gPkeO0VkbN98T1L2Usw5dCISnWuP2g5Q2+DPM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763546123; c=relaxed/simple; bh=mrVGDGmdBwi9bp1Ejm5GWoCivDI1+7VKZSTga3B+PrE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BhoChP+5gAgqRAkozpGTOmc1+UCjQ6oYbLACv0QF6pPKiNfpYi/RBKKRuJCuztQGcZToMPTC9Gf5PtWxOLCVIxcXhbp7FbAsOKJ1XJ0auY5s8HtOdAMlYQazya1uDxGw+VwMNbq2JmQHKQy7iR8G1t3XD3eY6BWdg/YjJgyQ094= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=alOJWxNc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="alOJWxNc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E9E4C2BCB8; Wed, 19 Nov 2025 09:55:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763546122; bh=mrVGDGmdBwi9bp1Ejm5GWoCivDI1+7VKZSTga3B+PrE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=alOJWxNcB+IkVtIDy2pVEUyd3HFS7OmaPY1pgPwYQvu0rHyh4x9n+9brKyMNnQv/v Qq/pe+VC1Nn/fpd6n+LbqNwfMRfVwcZyFTRG9+u0KDEVY3w/5Nv8tE9d3P22QKl/hD ztmwVEfvJ0g6Z2VTO63PE09RkTkimEuutWrCDWxFDze1ym4BLGuNL9hxxXIht6x24v CYHHKFl99vhFfpGb9egB0srcRsR/HhSNEixF0MUs7KHQ+lo8AjkCSqBApb9DMnEPwH M8L5MtlUI6wysxhIXBD2Z4QIm/rkq6+k+Vo8w9R9p7oCQKVHOUgpNF1oEmeNXonWg1 E0y9b6mcngrEQ== Date: Wed, 19 Nov 2025 11:55:16 +0200 From: Leon Romanovsky To: Christoph Hellwig Cc: Jens Axboe , Keith Busch , Sagi Grimberg , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Chaitanya Kulkarni Subject: Re: [PATCH v2 1/2] nvme-pci: Use size_t for length fields to handle larger sizes Message-ID: <20251119095516.GA13783@unreal> References: <20251117-nvme-phys-types-v2-0-c75a60a2c468@nvidia.com> <20251117-nvme-phys-types-v2-1-c75a60a2c468@nvidia.com> <20251118050311.GA21569@lst.de> 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: <20251118050311.GA21569@lst.de> On Tue, Nov 18, 2025 at 06:03:11AM +0100, Christoph Hellwig wrote: > On Mon, Nov 17, 2025 at 09:22:43PM +0200, Leon Romanovsky wrote: > > From: Leon Romanovsky > > > > This patch changes the length variables from unsigned int to size_t. > > Using size_t ensures that we can handle larger sizes, as size_t is > > always equal to or larger than the previously used u32 type. > > > > Originally, u32 was used because blk-mq-dma code evolved from > > scatter-gather implementation, which uses unsigned int to describe length. > > This change will also allow us to reuse the existing struct phys_vec in places > > that don't need scatter-gather. > > > > Signed-off-by: Leon Romanovsky > > Reviewed-by: Chaitanya Kulkarni > > --- > > block/blk-mq-dma.c | 8 ++++++-- > > drivers/nvme/host/pci.c | 4 ++-- > > 2 files changed, 8 insertions(+), 4 deletions(-) > > > > diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c > > index e9108ccaf4b0..e7d9b54c3eed 100644 > > --- a/block/blk-mq-dma.c > > +++ b/block/blk-mq-dma.c > > @@ -8,7 +8,7 @@ > > > > struct phys_vec { > > phys_addr_t paddr; > > - u32 len; > > + size_t len; > > }; > > So we're now going to increase memory usage by 50% again after just > reducing it by removing the scatterlist? It is slightly less. Before this change: 96 bits After this change (on 64bits system): 128 bits. It is 33% increase per-structure. So what is the resolution? Should I drop this patch or not? Thanks