linux-kernel - Re: [PATCH 5.12 038/127] btrfs: zoned: fix parallel compressed writes

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Date:   Tue, 25 May 2021 14:00:54 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        David Sterba <dsterba@...e.com>,
        Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH 5.12 038/127] btrfs: zoned: fix parallel compressed writes

On Mon, May 24, 2021 at 05:25:55PM +0200, Greg Kroah-Hartman wrote:
> From: Johannes Thumshirn <johannes.thumshirn@....com>
> 
> commit 764c7c9a464b68f7c6a5a9ec0b923176a05e8e8f upstream.
> 
> When multiple processes write data to the same block group on a
> compressed zoned filesystem, the underlying device could report I/O
> errors and data corruption is possible.
> 
> This happens because on a zoned file system, compressed data writes
> where sent to the device via a REQ_OP_WRITE instead of a
> REQ_OP_ZONE_APPEND operation. But with REQ_OP_WRITE and parallel
> submission it cannot be guaranteed that the data is always submitted
> aligned to the underlying zone's write pointer.
> 
> The change to using REQ_OP_ZONE_APPEND instead of REQ_OP_WRITE on a
> zoned filesystem is non intrusive on a regular file system or when
> submitting to a conventional zone on a zoned filesystem, as it is
> guarded by btrfs_use_zone_append.
> 
> Reported-by: David Sterba <dsterba@...e.com>
> Fixes: 9d294a685fbc ("btrfs: zoned: enable to mount ZONED incompat flag")
> CC: stable@...r.kernel.org # 5.12.x: e380adfc213a13: btrfs: zoned: pass start block to btrfs_use_zone_append
> CC: stable@...r.kernel.org # 5.12.x
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> Signed-off-by: David Sterba <dsterba@...e.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

We found a bug in this patch, please drop it from 5.12 queue.