On 02/02/2015 14:01, Christoph Hellwig wrote:
> This effectively reverts commits 85b6c7 ("[SCSI] sd: fix cache flushing on
> module removal (and individual device removal)" and dc4515ea ("scsi: always
> increment reference count").
>
> We now never call scsi_device_get from the shutdown path, and the fact
> that we started grabbing reference there in commit 85b6c7 turned out
> turned out to create more problems than it solves, and required
> workarounds for workarounds for workarounds. Move back to properly checking
> the device state and carefully handle module refcounting.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/scsi/scsi.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 9b38299..9b7fd0b 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -979,18 +979,24 @@ EXPORT_SYMBOL(scsi_report_opcode);
> * Description: Gets a reference to the scsi_device and increments the use count
> * of the underlying LLDD module. You must hold host_lock of the
> * parent Scsi_Host or already have a reference when calling this.
> + *
> + * This will fail if a device is deleted or cancelled, or when the LLD module
> + * is in the process of being unloaded.
> */
> int scsi_device_get(struct scsi_device *sdev)
> {
> - if (sdev->sdev_state == SDEV_DEL)
> - return -ENXIO;
> + if (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL)
> + goto fail;
> if (!get_device(&sdev->sdev_gendev))
> - return -ENXIO;
> - /* We can fail try_module_get if we're doing SCSI operations
> - * from module exit (like cache flush) */
> - __module_get(sdev->host->hostt->module);
> -
> + goto fail;
> + if (!try_module_get(sdev->host->hostt->module))
> + goto fail_put_device;
> return 0;
> +
> +fail_put_device:
> + put_device(&sdev->sdev_gendev);
> +fail:
> + return -ENXIO;
> }
> EXPORT_SYMBOL(scsi_device_get);
>
>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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