[SCSI] fcoe, libfc: adds offload EM per eth device with only single xid range per EM

Updates fcoe_em_config to allocate a single instance of sharable offload
EM for supported lp->lro_xid per eth device, and then share this EM
for subsequently more lports creation on same eth device (e.g when using
VLAN).

Adds tiny fcoe_oem_match function for offload EM to return true for read
types IO to have read IO exchanges allocated from offload shared EM.

Removes fc_em_alloc_xid function completely which was needed to manage
two xid ranges within a EM, this is not needed any more with allocation
of separate sharable offload EM per eth device. Instead this patch adds
simple xid allocation logic to manage single xid range.

Adds fc_exch_em_alloc with mp->next_xid as cursor to allocate new xid
from single xid range of EM, uses mp->next_xid instead removed mp->last_xid
which slightly increase probability of finding empty xid on exch allocation.

Removes restriction of not allowing use of xid zero along with changing
two xid range change to single xid range.

Makes fc_fcp_ddp_setup calling conditional to only xid allocated from
shared offload EM.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 65 insertions, 2 deletions

diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index 86410b9a30c3..0306aa95eb34 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -415,6 +415,17 @@ static int fcoe_shost_config(struct fc_lport *lp, struct Scsi_Host *shost,
         return 0;
 }
 
+/*
+ * fcoe_oem_match() - match for read types IO
+ * @fp: the fc_frame for new IO.
+ *
+ * Returns : true for read types IO, otherwise returns false.
+ */
+bool fcoe_oem_match(struct fc_frame *fp)
+{
+        return fc_fcp_is_read(fr_fsp(fp));
+}
+
 /**
  * fcoe_em_config() - allocates em for this lport
  * @lp: the port that em is to allocated for
@@ -425,9 +436,61 @@ static int fcoe_shost_config(struct fc_lport *lp, struct Scsi_Host *shost,
  */
 static inline int fcoe_em_config(struct fc_lport *lp)
 {
-        if (!fc_exch_mgr_alloc(lp, FC_CLASS_3, FCOE_MIN_XID,
-                               FCOE_MAX_XID, NULL))
+        struct fcoe_softc *fc = lport_priv(lp);
+        struct fcoe_softc *oldfc = NULL;
+        u16 min_xid = FCOE_MIN_XID;
+        u16 max_xid = FCOE_MAX_XID;
+
+        /*
+         * Check if need to allocate an em instance for
+         * offload exchange ids to be shared across all VN_PORTs/lport.
+         */
+        if (!lp->lro_enabled || !lp->lro_xid || (lp->lro_xid >= max_xid)) {
+                lp->lro_xid = 0;
+                goto skip_oem;
+        }
+
+        /*
+         * Reuse existing offload em instance in case
+         * it is already allocated on phys_dev.
+         */
+        list_for_each_entry(oldfc, &fcoe_hostlist, list) {
+                if (oldfc->phys_dev == fc->phys_dev) {
+                        fc->oem = oldfc->oem;
+                        break;
+                }
+        }
+
+        if (fc->oem) {
+                if (!fc_exch_mgr_add(lp, fc->oem, fcoe_oem_match)) {
+                        printk(KERN_ERR "fcoe_em_config: failed to add "
+                               "offload em:%p on interface:%s\n",
+                               fc->oem, fc->real_dev->name);
+                        return -ENOMEM;
+                }
+        } else {
+                fc->oem = fc_exch_mgr_alloc(lp, FC_CLASS_3,
+                                            FCOE_MIN_XID, lp->lro_xid,
+                                            fcoe_oem_match);
+                if (!fc->oem) {
+                        printk(KERN_ERR "fcoe_em_config: failed to allocate "
+                               "em for offload exches on interface:%s\n",
+                               fc->real_dev->name);
+                        return -ENOMEM;
+                }
+        }
+
+        /*
+         * Exclude offload EM xid range from next EM xid range.
+         */
+        min_xid += lp->lro_xid + 1;
+
+skip_oem:
+        if (!fc_exch_mgr_alloc(lp, FC_CLASS_3, min_xid, max_xid, NULL)) {
+                printk(KERN_ERR "fcoe_em_config: failed to "
+                       "allocate em on interface %s\n", fc->real_dev->name);
                 return -ENOMEM;
+        }
 
         return 0;
 }