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Thu, 14 Sep 2023 18:25:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id wmGLAiFQA2XWZAAAMHmgww (envelope-from ); Thu, 14 Sep 2023 18:25:37 +0000 Date: Thu, 14 Sep 2023 20:25:34 +0200 From: David Sterba To: Johannes Thumshirn Cc: Chris Mason , Josef Bacik , David Sterba , Christoph Hellwig , Naohiro Aota , Qu Wenruo , Damien Le Moal , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 00/11] btrfs: introduce RAID stripe tree Message-ID: <20230914182534.GD20408@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <20230914-raid-stripe-tree-v9-0-15d423829637@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230914-raid-stripe-tree-v9-0-15d423829637@wdc.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 14, 2023 at 09:06:55AM -0700, Johannes Thumshirn wrote: > Updates of the raid-stripe-tree are done at ordered extent write time to safe > on bandwidth while for reading we do the stripe-tree lookup on bio mapping > time, i.e. when the logical to physical translation happens for regular btrfs > RAID as well. > > The stripe tree is keyed by an extent's disk_bytenr and disk_num_bytes and > it's contents are the respective physical device id and position. > > For an example 1M write (split into 126K segments due to zone-append) > rapido2:/home/johannes/src/fstests# xfs_io -fdc "pwrite -b 1M 0 1M" -c fsync /mnt/test/test > wrote 1048576/1048576 bytes at offset 0 > 1 MiB, 1 ops; 0.0065 sec (151.538 MiB/sec and 151.5381 ops/sec) > > The tree will look as follows (both 128k buffered writes to a ZNS drive): > > RAID0 case: > bash-5.2# btrfs inspect-internal dump-tree -t raid_stripe /dev/nvme0n1 > btrfs-progs v6.3 > raid stripe tree key (RAID_STRIPE_TREE ROOT_ITEM 0) > leaf 805535744 items 1 free space 16218 generation 8 owner RAID_STRIPE_TREE > leaf 805535744 flags 0x1(WRITTEN) backref revision 1 > checksum stored 2d2d2262 > checksum calced 2d2d2262 > fs uuid ab05cfc6-9859-404e-970d-3999b1cb5438 > chunk uuid c9470ba2-49ac-4d46-8856-438a18e6bd23 > item 0 key (1073741824 RAID_STRIPE_KEY 131072) itemoff 16243 itemsize 56 > encoding: RAID0 > stripe 0 devid 1 offset 805306368 length 131072 > stripe 1 devid 2 offset 536870912 length 131072 > total bytes 42949672960 > bytes used 294912 > uuid ab05cfc6-9859-404e-970d-3999b1cb5438 > > RAID1 case: > bash-5.2# btrfs inspect-internal dump-tree -t raid_stripe /dev/nvme0n1 > btrfs-progs v6.3 > raid stripe tree key (RAID_STRIPE_TREE ROOT_ITEM 0) > leaf 805535744 items 1 free space 16218 generation 8 owner RAID_STRIPE_TREE > leaf 805535744 flags 0x1(WRITTEN) backref revision 1 > checksum stored 56199539 > checksum calced 56199539 > fs uuid 9e693a37-fbd1-4891-aed2-e7fe64605045 > chunk uuid 691874fc-1b9c-469b-bd7f-05e0e6ba88c4 > item 0 key (939524096 RAID_STRIPE_KEY 131072) itemoff 16243 itemsize 56 > encoding: RAID1 > stripe 0 devid 1 offset 939524096 length 65536 > stripe 1 devid 2 offset 536870912 length 65536 > total bytes 42949672960 > bytes used 294912 > uuid 9e693a37-fbd1-4891-aed2-e7fe64605045 > > A design document can be found here: > https://docs.google.com/document/d/1Iui_jMidCd4MVBNSSLXRfO7p5KmvnoQL/edit?usp=sharing&ouid=103609947580185458266&rtpof=true&sd=true Please also turn it to developer documentation file (in btrfs-progs/Documentation/dev), it can follow the same structure. > > The user-space part of this series can be found here: > https://lore.kernel.org/linux-btrfs/20230215143109.2721722-1-johannes.thumshirn@wdc.com > > Changes to v8: > - Changed tracepoints according to David's comments > - Mark on-disk structures as packed > - Got rid of __DECLARE_FLEX_ARRAY > - Rebase onto misc-next > - Split out helpers for new btrfs_load_block_group_zone_info RAID cases > - Constify declarations where possible > - Initialise variables before use > - Lower scope of variables > - Remove btrfs_stripe_root() helper > - Pick different BTRFS_RAID_STRIPE_KEY constant > - Reorder on-disk encoding types to match the raid_index > - And possibly more, please git range-diff the versions > - Link to v8: https://lore.kernel.org/r/20230911-raid-stripe-tree-v8-0-647676fa852c@wdc.com v9 will be added as topic branch to for-next, I did several style changes so please send any updates as incrementals if needed.