linux-kernel - Re: [PATCH 01/19] char_dev: replace cdev

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Date:   Thu, 27 Aug 2020 10:55:20 +0200
From:   Christoph Hellwig <hch@....de>
To:     Hannes Reinecke <hare@...e.de>
Cc:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Denis Efremov <efremov@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Song Liu <song@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-m68k@...ts.linux-m68k.org
Subject: Re: [PATCH 01/19] char_dev: replace cdev_map with an xarray

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.