On Thu, 2015-08-27 at 14:41 +0200, Hannes Reinecke wrote:
> Add a function scsi_vpd_lun_id() to return a unique device
> identifcation based on the designation descriptors of
> VPD page 0x83.
>
> As devices might implement several descriptors the order
> of preference is:
> - NAA IEE Registered Extended
> - EUI-64 based 16-byte
> - EUI-64 based 12-byte
> - NAA IEEE Registered
> - NAA IEEE Extended
> A SCSI name string descriptor is preferred to all of them
> if the identification is longer than 16 bytes.
>
> The returned unique device identification will be formatted
> as a SCSI Name string to avoid clashes between different
> designator types.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/scsi/scsi_lib.c | 121 +++++++++++++++++++++++++++++++++++++++++++++
> include/scsi/scsi_device.h | 1 +
> 2 files changed, 122 insertions(+)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 2a864b8..48d6ff6 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -3145,3 +3145,124 @@ void sdev_enable_disk_events(struct scsi_device *sdev)
> atomic_dec(&sdev->disk_events_disable_depth);
> }
> EXPORT_SYMBOL(sdev_enable_disk_events);
> +
> +/*
> + * scsi_vpd_lun_id - return a unique device identification
> + * @sdev: SCSI device
> + * @id: buffer for the identification
> + * @id_len: length of the buffer
> + *
> + * Copies a unique device identification into @id based
> + * on the information in the VPD page 0x83 of the device.
> + * The string will be formatted as a SCSI name string.
> + *
> + * Returns the length of the identification or error on failure.
> + */
> +int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
> +{
> + u8 cur_id_type = 0xff;
> + u8 cur_id_size = 0;
> + unsigned char *d, *cur_id_str;
> + int id_size = -EAGAIN;
> +
> + /*
> + * Look for the correct descriptor.
> + * Order of preference for lun descriptor:
> + * - SCSI name string
> + * - NAA IEEE Registered Extended
> + * - EUI-64 based 16-byte
> + * - EUI-64 based 12-byte
> + * - NAA IEEE Registered
> + * - NAA IEEE Extended
> + * as longer descriptors reduce the likelyhood
> + * of identification clashes.
> + */
> +
> + /* The id string must be at least 20 bytes + terminating NULL byte */
> + if (id_len < 21)
> + return -EINVAL;
> +
> + memset(id, 0, id_len);
> + d = sdev->vpd_pg83 + 4;
> + while (d < sdev->vpd_pg83 + sdev->vpd_pg83_len) {
> + /* Skip designators not referring to the LUN */
> + if ((d[1] & 0x30) != 0x00)
> + goto next_desig;
> +
> + switch (d[1] & 0xf) {
> + case 0x2:
> + /* EUI-64 */
> + if (cur_id_size > d[3])
> + break;
> + /* Prefer NAA IEEE Registered Extended */
> + if (cur_id_type == 0x3 &&
> + cur_id_size == d[3])
> + break;
> + cur_id_size = d[3];
> + cur_id_str = d + 4;
> + cur_id_type = d[1] & 0xf;
> + switch (cur_id_size) {
> + case 8:
> + id_size = snprintf(id, id_len,
> + "eui.%8phN",
> + cur_id_str);
> + break;
> + case 12:
> + id_size = snprintf(id, id_len,
> + "eui.%12phN",
> + cur_id_str);
> + break;
> + case 16:
> + id_size = snprintf(id, id_len,
> + "eui.%16phN",
> + cur_id_str);
> + break;
> + default:
> + cur_id_size = 0;
> + break;
> + }
> + break;
> + case 0x3:
> + /* NAA */
> + if (cur_id_size > d[3])
> + break;
> + cur_id_size = d[3];
> + cur_id_str = d + 4;
> + cur_id_type = d[1] & 0xf;
> + switch (cur_id_size) {
> + case 8:
> + id_size = snprintf(id, id_len,
> + "naa.%8phN",
> + cur_id_str);
> + break;
> + case 16:
> + id_size = snprintf(id, id_len,
> + "naa.%16phN",
> + cur_id_str);
> + break;
> + default:
> + cur_id_size = 0;
> + break;
> + }
> + break;
> + case 0x8:
> + /* SCSI name string */
> + if (cur_id_size + 4 > d[3])
> + break;
> + cur_id_size = d[3];
> + cur_id_str = d + 4;
> + cur_id_type = d[1] & 0xf;
> + if (cur_id_size >= id_len)
> + cur_id_size = id_len - 1;
> + memcpy(id, cur_id_str, cur_id_size);
> + break;
> + default:
> + break;
> + }
> +next_desig:
> + d += d[3] + 4;
> + }
> +
> + return id_size;
> +}
> +EXPORT_SYMBOL(scsi_vpd_lun_id);
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index b6b1dc4..595a9be 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -413,6 +413,7 @@ static inline int scsi_execute_req(struct scsi_device *sdev,
> }
> extern void sdev_disable_disk_events(struct scsi_device *sdev);
> extern void sdev_enable_disk_events(struct scsi_device *sdev);
> +extern int scsi_vpd_lun_id(struct scsi_device *, char *, size_t);
>
> #ifdef CONFIG_PM
> extern int scsi_autopm_get_device(struct scsi_device *);
scsi_vpd_lun_id() is an exported function, but does not check if sdev->vpd_pg83 != NULL
(i.e. no VPD 83 info), and we will crash if it is NULL. Also, why return -EAGAIN?
What will be different next time? Maybe a different errno would be better, like
-ENOENT or -ENODATA, I'm not sure.
In the SCSI name string case, if the name has to be truncated to fit the supplied buffer,
scsi_vpd_lun_id() does not ensure that the last byte is zero, it relies on the caller to
have done this, (which alua_check_vpd() does not do). I'm not sure if we should truncate
the SCSI name string here or return an error here, as a truncated name will likely not
be unique.
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
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