linux-kernel - Re: [PATCH] zram: close udev startup race condition as default groups

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Date:   Wed, 14 Nov 2018 08:09:23 +0100
From:   Hannes Reinecke <hare@...e.com>
To:     Minchan Kim <minchan@...nel.org>, stable@...r.kernel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Howard Chen <howardsoc@...gle.com>
Subject: Re: [PATCH] zram: close udev startup race condition as default groups

On 11/14/18 6:52 AM, Minchan Kim wrote:
> commit fef912bf860e upstream.
> commit 98af4d4df889 upstream.
> 
> I got a report from Howard Chen that he saw zram and sysfs race(ie,
> zram block device file is created but sysfs for it isn't yet)
> when he tried to create new zram devices via hotadd knob.
> 
> v4.20 kernel fixes it by [1, 2] but it's too large size to merge
> into -stable so this patch fixes the problem by registering defualt
> group by Greg KH's approach[3].
> 
> This patch should be applied to every stable tree [3.16+] currently
> existing from kernel.org because the problem was introduced at 2.6.37
> by [4].
> 
> [1] fef912bf860e, block: genhd: add 'groups' argument to device_add_disk
> [2] 98af4d4df889, zram: register default groups with device_add_disk()
> [3] http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/
> [4] 33863c21e69e9, Staging: zram: Replace ioctls with sysfs interface
> 
> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Cc: Hannes Reinecke <hare@...e.com>
> Tested-by: Howard Chen <howardsoc@...gle.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>   drivers/block/zram/zram_drv.c | 26 ++++++--------------------
>   1 file changed, 6 insertions(+), 20 deletions(-)
> 
Actually, I have a similar patch for NVMe in older revisions, so maybe I 
should push it to -stable, too.

Reviewed-by: Hannes Reinecke <hare@...e.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@...e.com			               +49 911 74053 688
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