Re: [PATCH v10] btrfs: consolidate device_list_mutex in prepare_sprout to its parent

From: David Sterba <dsterba@suse.cz>
To: Anand Jain <anand.jain@oracle.com>
Cc: linux-btrfs@vger.kernel.org, dsterba@suse.com,
	Josef Bacik <josef@toxicpanda.com>
Subject: Re: [PATCH v10] btrfs: consolidate device_list_mutex in prepare_sprout to its parent
Date: Tue, 9 Nov 2021 15:14:05 +0100	[thread overview]
Message-ID: <20211109141405.GR28560@twin.jikos.cz> (raw)
In-Reply-To: <31950264637728c53f794571354ef91842c6ea59.1636443598.git.anand.jain@oracle.com>

On Tue, Nov 09, 2021 at 05:51:58PM +0800, Anand Jain wrote:
> btrfs_prepare_sprout() splices seed devices into its own struct fs_devices,
> so that its parent function btrfs_init_new_device() can add the new sprout
> device to fs_info->fs_devices.
> 
> Both btrfs_prepare_sprout() and btrfs_init_new_device() needs
> device_list_mutex. But they are holding it sequentially, thus creates a
> small window to an opportunity to race. Close this opportunity and hold
> device_list_mutex common to both btrfs_init_new_device() and
> btrfs_prepare_sprout().
> 
> This patch splits btrfs_prepare_sprout() into btrfs_init_sprout() and
> btrfs_setup_sprout(). This split is essential because device_list_mutex
> shouldn't be held for allocs in btrfs_init_sprout() but must be held for
> btrfs_setup_sprout(). So now a common device_list_mutex can be used
> between btrfs_init_new_device() and btrfs_setup_sprout().
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> ---
> v10:
>  %ret should carry the error code from the init sprout, thx David.
> 
> v9:
>  Moved back the lockdep_assert_held(&uuid_mutex) to the top of the func
>    per Josef comment.
>  Add Josef RB.

Added to misc-next, thanks.