[PATCH] pktcdvd: bio write congestion using congestion_wait()
This adds a bio write queue congestion control to the pktcdvd driver with
fixed on/off marks. It prevents that the driver consumes a unlimited
amount of write requests.
[akpm@osdl.org: sync with congestion_wait() renaming]
Signed-off-by: Thomas Maier <balagi@justmail.de>
Cc: Peter Osterlund <petero2@telia.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 7e7b892..91fbe7f 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -84,6 +84,8 @@
static struct pktcdvd_device *pkt_devs[MAX_WRITERS];
static struct proc_dir_entry *pkt_proc;
static int pktdev_major;
+static int write_congestion_on = PKT_WRITE_CONGESTION_ON;
+static int write_congestion_off = PKT_WRITE_CONGESTION_OFF;
static struct mutex ctl_mutex; /* Serialize open/close/setup/teardown */
static mempool_t *psd_pool;
@@ -894,6 +896,7 @@
sector_t zone = 0; /* Suppress gcc warning */
struct pkt_rb_node *node, *first_node;
struct rb_node *n;
+ int wakeup;
VPRINTK("handle_queue\n");
@@ -966,7 +969,13 @@
pkt->write_size += bio->bi_size / CD_FRAMESIZE;
spin_unlock(&pkt->lock);
}
+ /* check write congestion marks, and if bio_queue_size is
+ below, wake up any waiters */
+ wakeup = (pd->write_congestion_on > 0
+ && pd->bio_queue_size <= pd->write_congestion_off);
spin_unlock(&pd->lock);
+ if (wakeup)
+ blk_clear_queue_congested(pd->disk->queue, WRITE);
pkt->sleep_time = max(PACKET_WAIT_TIME, 1);
pkt_set_state(pkt, PACKET_WAITING_STATE);
@@ -2179,6 +2188,23 @@
}
spin_unlock(&pd->cdrw.active_list_lock);
+ /*
+ * Test if there is enough room left in the bio work queue
+ * (queue size >= congestion on mark).
+ * If not, wait till the work queue size is below the congestion off mark.
+ */
+ spin_lock(&pd->lock);
+ if (pd->write_congestion_on > 0
+ && pd->bio_queue_size >= pd->write_congestion_on) {
+ blk_set_queue_congested(q, WRITE);
+ do {
+ spin_unlock(&pd->lock);
+ congestion_wait(WRITE, HZ);
+ spin_lock(&pd->lock);
+ } while(pd->bio_queue_size > pd->write_congestion_off);
+ }
+ spin_unlock(&pd->lock);
+
/*
* No matching packet found. Store the bio in the work queue.
*/
@@ -2298,6 +2324,9 @@
seq_printf(m, "\tstate:\t\t\ti:%d ow:%d rw:%d ww:%d rec:%d fin:%d\n",
states[0], states[1], states[2], states[3], states[4], states[5]);
+ seq_printf(m, "\twrite congestion marks:\toff=%d on=%d\n",
+ pd->write_congestion_off,
+ pd->write_congestion_on);
return 0;
}
@@ -2474,6 +2503,9 @@
init_waitqueue_head(&pd->wqueue);
pd->bio_queue = RB_ROOT;
+ pd->write_congestion_on = write_congestion_on;
+ pd->write_congestion_off = write_congestion_off;
+
disk = alloc_disk(1);
if (!disk)
goto out_mem;