From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38EA5C433F5 for ; Wed, 30 Mar 2022 16:03:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348496AbiC3QFE (ORCPT ); Wed, 30 Mar 2022 12:05:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347537AbiC3QFD (ORCPT ); Wed, 30 Mar 2022 12:05:03 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 964C2223224 for ; Wed, 30 Mar 2022 09:03:17 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id j13so20809474plj.8 for ; Wed, 30 Mar 2022 09:03:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=8ABS5RaDizOOxxZFwl9O2FRDLc7MT+a0LL7KHwTVFfs=; b=wbEAVtmOaNk8ULWhkU3abb9TRZoVeC7dF/LvVJaJLjuqC975dusSyXqcE7NoSHArTX SUiv/VzTSAHIYUXXHdsE36zXOzQv/McUvL3wCdaV4TT0CUrQz50id7uGglrwgHyZf2nS QZpTRW/R/nKOKZt6UAn4l/hkQJJVtYvy7iKfvgTMBSKCm0xA9V5KWHzvkNo4UWb1YK/Q tkX6Eqp6QyrCBcmeGwJ7GeaKsELD+5SkUQ68xdPFhc4FvXkpFRYZoP3udJKcH8NNY5CR nyKV8js9JHs/lebhROAbpmFhfyK6lboevmutBN6UT37Vi5c9qaykRftfzU2bw6DBlHhs 2j5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=8ABS5RaDizOOxxZFwl9O2FRDLc7MT+a0LL7KHwTVFfs=; b=rfw3g7UuI/WtVeCVg17xskrOueX0zvddsdMsY4JReJiQjzijTq0eJGi6uRgUvbdmSq L3sGojyQKZ/M+StCy1Gq2gffARvWU7MTjEycjft7KsNo4iZKFVqjCCYr/2OpDDf4VaWg qmkarohv5Tzv9w2bHMqLMYM0hF7CrxAzwo1dqQDMhcHEM23AfjQKMjBUkazaQOjXtCN0 TTvm56/LhsxpykgLtR1TFZSZXzN03fST4bSU4BCILYxi+wEXz1ejTbC99jikHqHv9C7l L1/HX21Qsisx/1eVmqRls9qDL/pbsX/3KBBbTn+v5JhtoHmhkZt8dAyR0qCWL8me+Ch1 8k/g== X-Gm-Message-State: AOAM530SCIUbAYPi3yNpUWUMWbEWyGAgwtGs6Tdl34GQ9a532AlbyTe5 ni5pa4zNFxvpo3hRtVoTVs0zwg== X-Google-Smtp-Source: ABdhPJyNP+ko8653MxRYs+qCjoycO5v/hMO9ctN6MYYLdfFjR2NL/EtY2W76uFHVc1M4sgqCwuI33Q== X-Received: by 2002:a17:902:ce8e:b0:154:2ebc:8d49 with SMTP id f14-20020a170902ce8e00b001542ebc8d49mr269232plg.135.1648656196988; Wed, 30 Mar 2022 09:03:16 -0700 (PDT) Received: from relinquished.localdomain ([2620:10d:c090:400::5:3897]) by smtp.gmail.com with ESMTPSA id a11-20020a63cd4b000000b00378b9167493sm20084837pgj.52.2022.03.30.09.03.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Mar 2022 09:03:16 -0700 (PDT) Date: Wed, 30 Mar 2022 09:03:14 -0700 From: Omar Sandoval To: Sweet Tea Dorminy Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v14 5/7] btrfs: send: allocate send buffer with alloc_page() and vmap() for v2 Message-ID: References: <4353fe7122eb0aae24e3c9ff2399f2b58b74f79e.1647537027.git.osandov@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Mar 24, 2022 at 01:53:20PM -0400, Sweet Tea Dorminy wrote: > > > On 3/17/22 13:25, Omar Sandoval wrote: > > From: Omar Sandoval > > > > For encoded writes, we need the raw pages for reading compressed data > > directly via a bio. > Perhaps: > "For encoded writes, the existing btrfs_encoded_read*() functions expect a > list of raw pages." > > I think it would be a better to continue just vmalloc'ing a large continuous > buffer and translating each page in the buffer into its raw page with > something like is_vmalloc_addr(data) ? vmalloc_to_page(data) : > virt_to_page(data). Vmalloc can request a higher-order allocation, which > probably doesn't matter but might slightly improve memory locality. And in > terms of readability, I somewhat like the elegance of having a single > identical kvmalloc call to allocate and send_buf in both cases, even if we > do need to initialize the page list for some v2 commands. I like this, but are we guaranteed that kvmalloc() will return a page-aligned buffer? It seems reasonable to me that it would for allocations of at least one page, but I can't find that written down anywhere.