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

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Date:   Fri, 16 Nov 2018 07:48:20 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     stable@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Hannes Reinecke <hare@...e.com>,
        Howard Chen <howardsoc@...gle.com>
Subject: Re: [PATCH] zram: close udev startup race condition as default groups

On Thu, Nov 15, 2018 at 12:45:04PM -0500, Sasha Levin wrote:
> On Wed, Nov 14, 2018 at 02:52:23PM +0900, 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>
> 
> I've queued this for 4.19 and 4.18, but it doesn't apply to anything
> older than that.

Thanks for the review, Hannes.

Sasha, I will send separate patches for older stable kernel.
Thanks for picking the patch.

> 
> --
> Thanks,
> Sasha