Re: [PATCH] scsi: avoid repetitive logging of device offline messages

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Mon, 2020-03-09 at 14:14 -0400, Ewan D. Milne wrote:
> Large queues of I/O to offline devices that are eventually
> submitted when devices are unblocked result in a many repeated
> "rejecting I/O to offline device" messages.  These messages
> can fill up the dmesg buffer in crash dumps so no useful
> prior messages remain.  In addition, if a serial console
> is used, the flood of messages can cause a hard lockup in
> the console code.
> 
> Introduce a flag indicating the message has already been logged
> for the device, and reset the flag when scsi_device_set_state()
> changes the device state.
> 
> Signed-off-by: Ewan D. Milne <emilne@redhat.com>
> ---
>  drivers/scsi/scsi_lib.c    | 8 ++++++--
>  include/scsi/scsi_device.h | 2 ++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 610ee41..d3a6d97 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1240,8 +1240,11 @@ scsi_prep_state_check(struct scsi_device
> *sdev, struct request *req)
>  		 * commands.  The device must be brought online
>  		 * before trying any recovery commands.
>  		 */
> -		sdev_printk(KERN_ERR, sdev,
> -			    "rejecting I/O to offline device\n");
> +		if (!sdev->offline_already) {
> +			sdev->offline_already = 1;
> +			sdev_printk(KERN_ERR, sdev,
> +				    "rejecting I/O to offline
> device\n");
> +		}

Offline->online is a legal transition, so you'll need to clear this
flag when that happens so we get another offline message if it goes
offline again.

James