linux-kernel - Re: [PATCH] drivers: base: Introduce a new kernel parameter driver_sync

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Message-ID: <2023120644-pry-worried-22a2@gregkh>
Date:   Wed, 6 Dec 2023 22:31:36 +0900
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     rafael@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: base: Introduce a new kernel parameter
 driver_sync_probe=

On Wed, Dec 06, 2023 at 11:53:55AM +0000, Yafang Shao wrote:
> After upgrading our kernel from version 4.19 to 6.1, certain regressions
> occurred due to the driver's asynchronous probe behavior. Specifically,
> the SCSI driver transitioned to an asynchronous probe by default, resulting
> in a non-fixed root disk behavior. In the prior 4.19 kernel, the root disk
> was consistently identified as /dev/sda. However, with kernel 6.1, the root
> disk can be any of /dev/sdX, leading to issues for applications reliant on
> /dev/sda, notably impacting monitoring systems monitoring the root disk.

Device names are never guaranteed to be stable, ALWAYS use a persistant
names like a filesystem label or other ways.  Look at /dev/disk/ for the
needed ways to do this properly.

> To address this, a new kernel parameter 'driver_sync_probe=' is introduced
> to enforce synchronous probe behavior for specific drivers.

This should be a per-bus thing, not a driver-specific thing as drivers
for the same bus could have differing settings here which would cause a
mess.

Please just revert the scsi bus functionality if you have had
regressions here, it's not a driver-core thing to do.

thanks,

greg k-h