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Subject: Re: rework check_disk_change()
To:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Cc:     Denis Efremov <efremov@linux.com>, Tim Waugh <tim@cyberelk.net>,
        Michal Simek <michal.simek@xilinx.com>,
        Borislav Petkov <bp@alien8.de>,
        "David S. Miller" <davem@davemloft.net>,
        Song Liu <song@kernel.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Finn Thain <fthain@telegraphics.com.au>,
        Michael Schmitz <schmitzmic@gmail.com>,
        linux-m68k@lists.linux-m68k.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org,
        linux-raid@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
References: <20200902141218.212614-1-hch@lst.de>
From:   Douglas Gilbert <dgilbert@interlog.com>
Message-ID: <730eced4-c804-a78f-3d52-2a448dbd1b84@interlog.com>
Date:   Wed, 2 Sep 2020 11:38:45 -0400
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On 2020-09-02 10:11 a.m., Christoph Hellwig wrote:
> Hi Jens,
> 
> this series replaced the not very nice check_disk_change() function with
> a new bdev_media_changed that avoids having the ->revalidate_disk call
> at its end.  As a result ->revalidate_disk can be removed from a lot of
> drivers.
> 

For over 20 years the sg driver has been carrying this snippet that hangs
off the completion callback:

        if (driver_stat & DRIVER_SENSE) {
                 struct scsi_sense_hdr ssh;

                 if (scsi_normalize_sense(sbp, sense_len, &ssh)) {
                         if (!scsi_sense_is_deferred(&ssh)) {
                                 if (ssh.sense_key == UNIT_ATTENTION) {
                                         if (sdp->device->removable)
                                                 sdp->device->changed = 1;
                                 }
                         }
                 }
         }

Is it needed? The unit attention (UA) may not be associated with the
device changing. Shouldn't the SCSI mid-level monitor UAs if they
impact the state of a scsi_device object?

Doug Gilbert