scsi: core: Don't start concurrent async scan on same host
[ Upstream commit 831e3405c2
]
The current scanning mechanism is supposed to fall back to a synchronous
host scan if an asynchronous scan is in progress. However, this rule isn't
strictly respected, scsi_prep_async_scan() doesn't hold scan_mutex when
checking shost->async_scan. When scsi_scan_host() is called concurrently,
two async scans on same host can be started and a hang in do_scan_async()
is observed.
Fixes this issue by checking & setting shost->async_scan atomically with
shost->scan_mutex.
Link: https://lore.kernel.org/r/20201010032539.426615-1-ming.lei@redhat.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
parent
3c52715cea
commit
fd4fb50807
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@ -1715,15 +1715,16 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
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*/
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*/
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static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
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static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
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{
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{
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struct async_scan_data *data;
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struct async_scan_data *data = NULL;
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unsigned long flags;
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unsigned long flags;
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if (strncmp(scsi_scan_type, "sync", 4) == 0)
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if (strncmp(scsi_scan_type, "sync", 4) == 0)
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return NULL;
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return NULL;
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mutex_lock(&shost->scan_mutex);
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if (shost->async_scan) {
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if (shost->async_scan) {
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shost_printk(KERN_DEBUG, shost, "%s called twice\n", __func__);
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shost_printk(KERN_DEBUG, shost, "%s called twice\n", __func__);
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return NULL;
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goto err;
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}
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}
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data = kmalloc(sizeof(*data), GFP_KERNEL);
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data = kmalloc(sizeof(*data), GFP_KERNEL);
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@ -1734,7 +1735,6 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
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goto err;
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goto err;
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init_completion(&data->prev_finished);
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init_completion(&data->prev_finished);
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mutex_lock(&shost->scan_mutex);
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spin_lock_irqsave(shost->host_lock, flags);
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spin_lock_irqsave(shost->host_lock, flags);
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shost->async_scan = 1;
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shost->async_scan = 1;
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spin_unlock_irqrestore(shost->host_lock, flags);
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spin_unlock_irqrestore(shost->host_lock, flags);
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@ -1749,6 +1749,7 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
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return data;
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return data;
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err:
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err:
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mutex_unlock(&shost->scan_mutex);
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kfree(data);
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kfree(data);
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return NULL;
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return NULL;
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}
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}
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