linux-kernel - Re: [PATCH] btrfs: extend locking to all space

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Message-ID: <PH0PR04MB741656BC63FF14D8995B46529B019@PH0PR04MB7416.namprd04.prod.outlook.com>
Date:   Mon, 28 Feb 2022 15:51:43 +0000
From:   Johannes Thumshirn <Johannes.Thumshirn@....com>
To:     Niels Dossche <dossche.niels@...il.com>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "clm@...com" <clm@...com>,
        "josef@...icpanda.com" <josef@...icpanda.com>,
        "dsterba@...e.com" <dsterba@...e.com>,
        Niels Dossche <niels.dossche@...nt.be>
Subject: Re: [PATCH] btrfs: extend locking to all space_info members accesses

On 25/02/2022 22:21, Niels Dossche wrote:
> bytes_pinned is always accessed under space_info->lock, except in
> btrfs_preempt_reclaim_metadata_space, however the other members are
> accessed under that lock. The reserved member of the rsv's are also
> partially accessed under a lock and partially not. Move all these
> accesses into the same lock to ensure consistency.

Maybe also add a lockdep_assert_held() call to need_preemptive_reclaim().

As of now, it has only two callsites which both hold the lock before
accessing bytes_pinned et al, but better safe then sorry.

Anyways,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>