This patch adds per disk queue functionality. It seems that the 2.6 kernel expects a queue per disk. If you have multiple logical drives on a controller all of the queues actually point back to the same queue. If a drive is deleted it blows us out of the water.
We hold the lock during any queue operations and have added what we call a
"fair-enough" algorithm to prevent starving out any drive.
Please consider this for inclusion.
Signed-off-by: Mike Miller <[email protected]>
cciss.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++----
cciss.h | 5 +++++
2 files changed, 53 insertions(+), 4 deletions(-)
----------------------------------------------------------------------------
diff -burNp lx2611-p002/drivers/block/cciss.c lx2611-p003/drivers/block/cciss.c
--- lx2611-p002/drivers/block/cciss.c 2005-03-08 16:50:47.149175280 -0600
+++ lx2611-p003/drivers/block/cciss.c 2005-03-08 17:17:50.148441888 -0600
@@ -2090,6 +2090,9 @@ static void do_cciss_request(request_que
drive_info_struct *drv;
int i, dir;
+ /* We call start_io here in case there is a command waiting on the
+ * queue that has not been sent.
+ */
if (blk_queue_plugged(q))
goto startio;
@@ -2178,6 +2181,9 @@ queue:
full:
blk_stop_queue(q);
startio:
+ /* We will already have the driver lock here so not need
+ * to lock it.
+ */
start_io(h);
}
@@ -2187,7 +2193,8 @@ static irqreturn_t do_cciss_intr(int irq
CommandList_struct *c;
unsigned long flags;
__u32 a, a1;
-
+ int j;
+ int start_queue = h->next_to_run;
/* Is this interrupt for us? */
if (( h->access.intr_pending(h) == 0) || (h->interrupts_enabled == 0))
@@ -2234,13 +2241,50 @@ static irqreturn_t do_cciss_intr(int irq
}
}
- /*
- * See if we can queue up some more IO
+ /* check to see if we have maxed out the number of commands that can
+ * be placed on the queue. If so then exit. We do this check here
+ * in case the interrupt we serviced was from an ioctl and did not
+ * free any new commands.
*/
- blk_start_queue(h->queue);
+ if ((find_first_zero_bit(h->cmd_pool_bits, NR_CMDS)) == NR_CMDS)
+ goto cleanup;
+
+ /* We have room on the queue for more commands. Now we need to queue
+ * them up. We will also keep track of the next queue to run so
+ * that every queue gets a chance to be started first.
+ */
+ for (j=0; j < NWD; j++){
+ int curr_queue = (start_queue + j) % NWD;
+ /* make sure the disk has been added and the drive is real
+ * because this can be called from the middle of init_one.
+ */
+ if(!(h->gendisk[curr_queue]->queue) ||
+ !(h->drv[curr_queue].heads))
+ continue;
+ blk_start_queue(h->gendisk[curr_queue]->queue);
+
+ /* check to see if we have maxed out the number of commands
+ * that can be placed on the queue.
+ */
+ if ((find_first_zero_bit(h->cmd_pool_bits, NR_CMDS)) == NR_CMDS)
+ {
+ if (curr_queue == start_queue){
+ h->next_to_run = (start_queue + 1) % NWD;
+ goto cleanup;
+ } else {
+ h->next_to_run = curr_queue;
+ goto cleanup;
+ }
+ } else {
+ curr_queue = (curr_queue + 1) % NWD;
+ }
+ }
+
+cleanup:
spin_unlock_irqrestore(CCISS_LOCK(h->ctlr), flags);
return IRQ_HANDLED;
}
+
/*
* We cannot read the structure directly, for portablity we must use
* the io functions.
Files lx2611-p002/drivers/block/.cciss.c.rej.swp and lx2611-p003/drivers/block/.cciss.c.rej.swp differ
diff -burNp lx2611-p002/drivers/block/cciss.h lx2611-p003/drivers/block/cciss.h
--- lx2611-p002/drivers/block/cciss.h 2005-03-08 16:50:47.150175128 -0600
+++ lx2611-p003/drivers/block/cciss.h 2005-03-08 17:03:04.279114496 -0600
@@ -84,6 +84,11 @@ struct ctlr_info
int nr_frees;
int busy_configuring;
+ /* This element holds the zero based queue number of the last
+ * queue to be started. It is used for fairness.
+ */
+ int next_to_run;
+
// Disk structures we need to pass back
struct gendisk *gendisk[NWD];
#ifdef CONFIG_CISS_SCSI_TAPE