On 4/8/2021 1:46 AM, Hannes Reinecke wrote:
On 4/7/21 1:06 AM, Muneendra wrote:
From: Gaurav Srivastava <gaurav.srivastava@xxxxxxxxxxxx>
...
+ /* while the read lock was released, in case the entry was */
+ /* added by other context or is in process of being added */
+ if (vmp && vmp->flag & LPFC_VMID_REGISTERED) {
+ lpfc_vmid_update_entry(vport, cmd, vmp, tag);
+ write_unlock(&vport->vmid_lock);
+ return 0;
+ } else if (vmp && vmp->flag & LPFC_VMID_REQ_REGISTER) {
+ write_unlock(&vport->vmid_lock);
+ return -EBUSY;
+ }
+
+ /* else search and allocate a free slot in the hash table */
+ if (vport->cur_vmid_cnt < vport->max_vmid) {
+ for (i = 0; i < vport->max_vmid; ++i) {
+ vmp = vport->vmid + i;
+ if (vmp->flag == LPFC_VMID_SLOT_FREE) {
+ vmp = vport->vmid + i;
delete this last line and adjust parens - really odd that it replicates
the assignment 2 lines earlier.
+ break;
+ }
+ }
I would prefer that if the table is expended and no slots free, that
-ENOMEM is returned here. Rather than falling down below and qualifying
by slot free, then by pending (set only if slot free). I can't believe
there is a reason the idle timer has to be started if no slots free as
all the other fail cases don't bother with it.
This also helps indentation levels below.
+ } else {
+ write_unlock(&vport->vmid_lock);
+ return -ENOMEM;
+ }
+
+ if (vmp && (vmp->flag == LPFC_VMID_SLOT_FREE)) {
+ /* Add the vmid and register */
+ lpfc_put_vmid_in_hashtable(vport, hash, vmp);
+ vmp->vmid_len = len;
+ memcpy(vmp->host_vmid, uuid, vmp->vmid_len);
+ vmp->io_rd_cnt = 0;
+ vmp->io_wr_cnt = 0;
+ vmp->flag = LPFC_VMID_SLOT_USED;
+
+ vmp->delete_inactive =
+ vport->vmid_inactivity_timeout ? 1 : 0;
+
+ /* if type priority tag, get next available vmid */
+ if (lpfc_vmid_is_type_priority_tag(vport))
+ lpfc_vmid_assign_cs_ctl(vport, vmp);
+
+ /* allocate the per cpu variable for holding */
+ /* the last access time stamp only if vmid is enabled */
+ if (!vmp->last_io_time)
+ vmp->last_io_time =
+ __alloc_percpu(sizeof(u64),
+ __alignof__(struct
+ lpfc_vmid));
+
+ /* registration pending */
+ pending = 1;
+ } else {
+ rc = -ENOMEM;
+ }
+ write_unlock(&vport->vmid_lock);
+
+ /* complete transaction with switch */
+ if (pending) {
+ if (lpfc_vmid_is_type_priority_tag(vport))
+ rc = lpfc_vmid_uvem(vport, vmp, true);
+ else
+ rc = lpfc_vmid_cmd(vport,
+ SLI_CTAS_RAPP_IDENT,
+ vmp);
+ if (!rc) {
+ write_lock(&vport->vmid_lock);
+ vport->cur_vmid_cnt++;
+ vmp->flag |= LPFC_VMID_REQ_REGISTER;
+ write_unlock(&vport->vmid_lock);
+ }
+ }
+
+ /* finally, enable the idle timer once */
+ if (!(vport->phba->pport->vmid_flag & LPFC_VMID_TIMER_ENBLD)) {
+ mod_timer(&vport->phba->inactive_vmid_poll,
+ jiffies +
+ msecs_to_jiffies(1000 * LPFC_VMID_TIMER));
+ vport->phba->pport->vmid_flag |= LPFC_VMID_TIMER_ENBLD;
+ }
+ }
+ return rc;
+}
+
+/*
+ * lpfc_is_command_vm_io - get the uuid from blk cgroup
+ * @cmd:Pointer to scsi_cmnd data structure
+ * Returns uuid if present if not null
+ */
+static char *lpfc_is_command_vm_io(struct scsi_cmnd *cmd)
+{
+ char *uuid = NULL;
+
+ if (cmd->request) {
+ if (cmd->request->bio)
+ uuid = blkcg_get_fc_appid(cmd->request->bio);
+ }
+ return uuid;
+}
+
/**
* lpfc_queuecommand - scsi_host_template queuecommand entry point
* @shost: kernel scsi host pointer.
@@ -5288,6 +5437,7 @@ lpfc_queuecommand(struct Scsi_Host *shost,
struct scsi_cmnd *cmnd)
int err, idx;
#ifdef CONFIG_SCSI_LPFC_DEBUG_FS
uint64_t start = 0L;
+ u8 *uuid = NULL;
if (phba->ktime_on)
start = ktime_get_ns();
@@ -5415,6 +5565,25 @@ lpfc_queuecommand(struct Scsi_Host *shost,
struct scsi_cmnd *cmnd)
}
+ /* check the necessary and sufficient condition to support VMID */
+ if (lpfc_is_vmid_enabled(phba) &&
+ (ndlp->vmid_support ||
+ phba->pport->vmid_priority_tagging ==
+ LPFC_VMID_PRIO_TAG_ALL_TARGETS)) {
+ /* is the IO generated by a VM, get the associated virtual */
+ /* entity id */
+ uuid = lpfc_is_command_vm_io(cmnd);
+
+ if (uuid) {
+ err = lpfc_vmid_get_appid(vport, uuid, cmnd,
+ (union lpfc_vmid_io_tag *)
+ &lpfc_cmd->cur_iocbq.vmid_tag);
+ if (!err)
+ lpfc_cmd->cur_iocbq.iocb_flag |= LPFC_IO_VMID;
+ }
+ }
+
+ atomic_inc(&ndlp->cmd_pending);
#ifdef CONFIG_SCSI_LPFC_DEBUG_FS
if (unlikely(phba->hdwqstat_on & LPFC_CHECK_SCSI_IO))
this_cpu_inc(phba->sli4_hba.c_stat->xmt_io);
And that's the bit which I don't particular like.
Essentially we'll have to inject additional ELS commands _on each I/O_
to get a valid VMID.
Where there are _so_ many things which might get wrong, causing an I/O
stall.
I don't follow you - yes ELS's are injected when there isn't an entry
for the VM, but once there is, there isn't further ELS's. That is the
cost. as we don't know what uuid's I/O will be sent to before hand, so
it has to be siphoned off during the I/O flow. I/O's can be sent
non-tagged while the ELS's are completing (and there aren't multiple
sets of ELS's as long as it's the same uuid), which is fine.
so I disagree with "_on each I/O_".
I would have vastly preferred if we could _avoid_ having to do
additional ELS commands for VMID registration in the I/O path
(ie only allow for I/O with a valid VMID), and reject the I/O otherwise
until VMID registration is complete.
IE return 'BUSY' (or even a command retry?) when no valid VMID for this
particular I/O is found, register the VMID (preferably in another
thread), and restart the queue once the VMID is registered.
Why does it bother you with the I/O path ? It's actually happening in
parallel with no real relation between the two.
I seriously disagree with reject if no vmid tag. Why? what do you gain
? This actually introduces more disruption than the parallel flow with
the ELSs. Also, after link bounce, where all VMID's have to be done,
it adds a stall window after link up right when things are trying to
resume after rports rejoin. Why add the i/o rebouncing ? There no real
benefit. Issuing a few untagged I/O doesn't hurt.
That way we have a clear separation, and the I/O path will always work
with valid VMIDs.
Hmm?
Cheers,
Hannes
-- james
