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Date:   Thu, 27 Aug 2020 10:55:20 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Hannes Reinecke <hare@suse.de>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Denis Efremov <efremov@linux.com>,
        "David S. Miller" <davem@davemloft.net>,
        Song Liu <song@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-ide@vger.kernel.org, linux-raid@vger.kernel.org,
        linux-scsi@vger.kernel.org, linux-m68k@lists.linux-m68k.org
Subject: Re: [PATCH 01/19] char_dev: replace cdev_map with an xarray
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On Thu, Aug 27, 2020 at 09:25:07AM +0200, Hannes Reinecke wrote:
> Do you really need the mutex?
> Wouldn't xa_store_range() be better and avoid the mutex?

We need the mutex as we need to grab the kobject reference under it.

xa_store_range is only available with a separate config option, and
has really strange calling conventions.  So I'd rather not pull it in
here, especially as most cdev_add callers are for a single minor only
anyway.