From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f196.google.com ([209.85.215.196]:42213 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727477AbeHJQyf (ORCPT ); Fri, 10 Aug 2018 12:54:35 -0400 Date: Fri, 10 Aug 2018 23:24:24 +0900 From: Naohiro Aota To: Hannes Reinecke , David Sterba , linux-btrfs@vger.kernel.org Cc: Chris Mason , Josef Bacik , linux-kernel@vger.kernel.org, Damien Le Moal , Bart Van Assche , Matias Bjorling Subject: Re: [RFC PATCH 00/17] btrfs zoned block device support Message-ID: <20180810142424.62linovnguszljzf@zazie> References: <20180809180450.5091-1-naota@elisp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, Aug 10, 2018 at 09:04:59AM +0200, Hannes Reinecke wrote: > On 08/09/2018 08:04 PM, Naohiro Aota wrote: > > This series adds zoned block device support to btrfs. > > > > A zoned block device consists of a number of zones. Zones are either > > conventional and accepting random writes or sequential and requiring that > > writes be issued in LBA order from each zone write pointer position. This > > patch series ensures that the sequential write constraint of sequential > > zones is respected while fundamentally not changing BtrFS block and I/O > > management for block stored in conventional zones. > > > > To achieve this, the default dev extent size of btrfs is changed on zoned > > block devices so that dev extents are always aligned to a zone. Allocation > > of blocks within a block group is changed so that the allocation is always > > sequential from the beginning of the block groups. To do so, an allocation > > pointer is added to block groups and used as the allocation hint. The > > allocation changes also ensures that block freed below the allocation > > pointer are ignored, resulting in sequential block allocation regardless of > > the block group usage. > > > > While the introduction of the allocation pointer ensure that blocks will be > > allocated sequentially, I/Os to write out newly allocated blocks may be > > issued out of order, causing errors when writing to sequential zones. This > > problem s solved by introducing a submit_buffer() function and changes to > > the internal I/O scheduler to ensure in-order issuing of write I/Os for > > each chunk and corresponding to the block allocation order in the chunk. > > > > The zones of a chunk are reset to allow reusing of the zone only when the > > block group is being freed, that is, when all the extents of the block group > > are unused. > > > > For btrfs volumes composed of multiple zoned disks, restrictions are added > > to ensure that all disks have the same zone size. This matches the existing > > constraint that all dev extents in a chunk must have the same size. > > > > It requires zoned block devices to test the patchset. Even if you don't > > have zone devices, you can use tcmu-runner [1] to emulate zoned block > > devices. It can export emulated zoned block devices via iSCSI. Please see > > the README.md of tcmu-runner [2] for howtos to generate a zoned block > > device on tcmu-runner. > > > > [1] https://github.com/open-iscsi/tcmu-runner > > [2] https://github.com/open-iscsi/tcmu-runner/blob/master/README.md > > > > Patch 1 introduces the HMZONED incompatible feature flag to indicate that > > the btrfs volume was formatted for use on zoned block devices. > > > > Patches 2 and 3 implement functions to gather information on the zones of > > the device (zones type and write pointer position). > > > > Patch 4 restrict the possible locations of super blocks to conventional > > zones to preserve the existing update in-place mechanism for the super > > blocks. > > > > Patches 5 to 7 disable features which are not compatible with the sequential > > write constraints of zoned block devices. This includes fallocate and > > direct I/O support. Device replace is also disabled for now. > > > > Patches 8 and 9 tweak the extent buffer allocation for HMZONED mode to > > implement sequential block allocation in block groups and chunks. > > > > Patches 10 to 12 implement the new submit buffer I/O path to ensure sequential > > write I/O delivery to the device zones. > > > > Patches 13 to 16 modify several parts of btrfs to handle free blocks > > without breaking the sequential block allocation and sequential write order > > as well as zone reset for unused chunks. > > > > Finally, patch 17 adds the HMZONED feature to the list of supported > > features. > > > Thanks for doing all the work. > However, the patches don't apply cleanly to current master branch. > Can you please rebase them? I'm currently basing on https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next branch, since my previous bug-fix patch 266e010932ce ("btrfs: revert fs_devices state on error of btrfs_init_new_device") is necessary to avoid use-after-free bug in error handling path of btrfs_init_new_device() in the patch 2. I'm sorry for not mentioning it. I'll rebase on the master branch when the patch reach the master. Regards, Naohiro > Thanks. > > Cheers, > > Hannes > -- > Dr. Hannes Reinecke zSeries & Storage > hare@suse.com +49 911 74053 688 > SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg > GF: F. Imendörffer, J. Smithard, D. Upmanyu, G. Norton > HRB 21284 (AG Nürnberg)