[SCSI] scsi_dh_alua: Inroduce the set_params interface scsi_dh_alua handler

Handler expects only one parameter to set the flag ALUA_OPTIMIZE_STPG.
This flag is used to optimize the STPG behaviour. There is no change in
behaviour by default.

For example, to set the flag pass the following parameters from multipath.conf
hardware_handler        "2 alua 1"

Signed-off-by: Babu Moger <babu.moger@netapp.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 04c5cea47a2258a2156f692a6441253db31a8506..506206ae575520f2bac742e7d72aee1e53af43f9 100644 (file)
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -55,11 +55,15 @@
 #define ALUA_FAILOVER_TIMEOUT          (60 * HZ)
 #define ALUA_FAILOVER_RETRIES          5
 
+/* flags passed from user level */
+#define ALUA_OPTIMIZE_STPG             1
+
 struct alua_dh_data {
        int                     group_id;
        int                     rel_port;
        int                     tpgs;
        int                     state;
+       unsigned                flags; /* used for optimizing STPG */
        unsigned char           inq[ALUA_INQUIRY_SIZE];
        unsigned char           *buff;
        int                     bufflen;
@@ -621,6 +625,37 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 out:
        return err;
 }
+/*
+ * alua_set_params - set/unset the optimize flag
+ * @sdev: device on the path to be activated
+ * params - parameters in the following format
+ *      "no_of_params\0param1\0param2\0param3\0...\0"
+ * For example, to set the flag pass the following parameters
+ * from multipath.conf
+ *     hardware_handler        "2 alua 1"
+ */
+static int alua_set_params(struct scsi_device *sdev, const char *params)
+{
+       struct alua_dh_data *h = get_alua_data(sdev);
+       unsigned int optimize = 0, argc;
+       const char *p = params;
+       int result = SCSI_DH_OK;
+
+       if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
+               return -EINVAL;
+
+       while (*p++)
+               ;
+       if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
+               return -EINVAL;
+
+       if (optimize)
+               h->flags |= ALUA_OPTIMIZE_STPG;
+       else
+               h->flags &= ~ALUA_OPTIMIZE_STPG;
+
+       return result;
+}
 
 /*
  * alua_activate - activate a path
@@ -698,6 +733,7 @@ static struct scsi_device_handler alua_dh = {
        .prep_fn = alua_prep_fn,
        .check_sense = alua_check_sense,
        .activate = alua_activate,
+       .set_params = alua_set_params,
        .match = alua_match,
 };