From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net ([212.227.17.22]:33483 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750891AbeEQIER (ORCPT ); Thu, 17 May 2018 04:04:17 -0400 Subject: Re: [PATCH 2/4] btrfs: lzo: Add comment about the how btrfs records its lzo compressed data To: Nikolay Borisov , Qu Wenruo , linux-btrfs@vger.kernel.org Cc: jamespharvey20@gmail.com References: <20180517062753.25973-1-wqu@suse.com> <20180517062753.25973-3-wqu@suse.com> From: Qu Wenruo Message-ID: <3fb51446-e04e-91a1-7699-243759edfd58@gmx.com> Date: Thu, 17 May 2018 16:04:02 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2018年05月17日 15:48, Nikolay Borisov wrote: > > > On 17.05.2018 09:27, Qu Wenruo wrote: >> Signed-off-by: Qu Wenruo > > Overall it looks good and useful just a couple of nits below. >> --- >> fs/btrfs/lzo.c | 23 +++++++++++++++++++++++ >> 1 file changed, 23 insertions(+) >> >> diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c >> index 0667ea07f766..3d2ae4c08876 100644 >> --- a/fs/btrfs/lzo.c >> +++ b/fs/btrfs/lzo.c >> @@ -17,6 +17,29 @@ >> >> #define LZO_LEN 4 >> >> +/* >> + * Btrfs LZO compression format >> + * >> + * Regular LZO compressed data extent is consist of: > nit: s/is consist/consists >> + * 1. Header >> + * Fixed size. LZO_LEN (4) bytes long, LE16. >> + * Records the total size (*includes* the header) of real compressed data. >> + * >> + * 2. Segment(s) >> + * Variable size. Includes one segment header, and then data payload. >> + * One btrfs compressed data can have one or more segments. > > So "one btrfs compressed data" should really mean "one btrfs compressed > extent" I guess? Oh, yes, one btrfs compressed extent. Thanks, Qu > >> + * >> + * 2.1 Segment header >> + * Fixed size. LZO_LEN (4) bytes long, LE16. >> + * Records the total size of the segment (*excludes* the header). >> + * >> + * 2.2 Data Payload >> + * Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE). >> + * >> + * While for inlined LZO compressed data extent, it doesn't have Header, just >> + * one Segment. > > > >> + */ >> + >> struct workspace { >> void *mem; >> void *buf; /* where decompressed data goes */ >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >