[PATCH 2/2] 2.6.19-rc1-mm1 pktcdvd: bio write congestion

Thomas Maier
2006-10-14T18:02:15Z

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Hello,

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.

Signed-off-by: Thomas Maier <balagi@justmail.de>

[-- Attachment #2: pktcdvd-2-wqueue-congestion.patch --]
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diff -urpN 1-init-pktdev_major/drivers/block/pktcdvd.c 2-wqueue-congestion/drivers/block/pktcdvd.c
--- 1-init-pktdev_major/drivers/block/pktcdvd.c 2006-10-14 13:50:54.000000000 +0200
+++ 2-wqueue-congestion/drivers/block/pktcdvd.c 2006-10-14 14:05:28.000000000 +0200
@@ -84,6 +84,8 @@
static struct pktcdvd_device *pkt_devs[MAX_WRITERS];
static struct proc_dir_entry *pkt_proc;
static int pktdev_major = 0;
+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 @@ static int pkt_handle_queue(struct pktcd
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 +969,14 @@ try_next_bio:
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
+ && waitqueue_active(&pd->write_congestion_wqueue));
spin_unlock(&pd->lock);
+ if (wakeup)
+ wake_up(&pd->write_congestion_wqueue);

pkt->sleep_time = max(PACKET_WAIT_TIME, 1);
pkt_set_state(pkt, PACKET_WAITING_STATE);
@@ -2180,6 +2190,31 @@ static int pkt_make_request(request_queu
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.
+ * This is similar to the get_request_wait() call made in the block
+ * layer function __make_request() used for normal block i/o request
+ * handling.
+ */
+ spin_lock(&pd->lock);
+ if (pd->write_congestion_on > 0
+ && pd->bio_queue_size >= pd->write_congestion_on) {
+ DEFINE_WAIT(wait);
+ do { /* wait till number of bio requests is low enough */
+ spin_unlock(&pd->lock);
+ prepare_to_wait_exclusive(&pd->write_congestion_wqueue,
+ &wait, TASK_UNINTERRUPTIBLE);
+ io_schedule();
+ /* if we are here, bio_queue_size should be below
+ congestion_off, but be sure and do a test */
+ spin_lock(&pd->lock);
+ } while(pd->bio_queue_size > pd->write_congestion_off);
+ finish_wait(&pd->write_congestion_wqueue, &wait);
+ }
+ spin_unlock(&pd->lock);
+
+ /*
* No matching packet found. Store the bio in the work queue.
*/
node = mempool_alloc(pd->rb_pool, GFP_NOIO);
@@ -2298,6 +2333,9 @@ static int pkt_seq_show(struct seq_file
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 +2512,10 @@ static int pkt_setup_dev(dev_t dev, dev_
init_waitqueue_head(&pd->wqueue);
pd->bio_queue = RB_ROOT;

+ init_waitqueue_head(&pd->write_congestion_wqueue);
+ pd->write_congestion_on = write_congestion_on;
+ pd->write_congestion_off = write_congestion_off;
+
disk = alloc_disk(1);
if (!disk)
goto out_mem;
diff -urpN 1-init-pktdev_major/include/linux/pktcdvd.h 2-wqueue-congestion/include/linux/pktcdvd.h
--- 1-init-pktdev_major/include/linux/pktcdvd.h 2006-10-14 13:49:52.000000000 +0200
+++ 2-wqueue-congestion/include/linux/pktcdvd.h 2006-10-14 13:58:16.000000000 +0200
@@ -112,6 +112,12 @@ struct pkt_ctrl_command {
#include <linux/completion.h>
#include <linux/cdrom.h>

+
+/* default bio write queue congestion marks */
+#define PKT_WRITE_CONGESTION_ON 10000
+#define PKT_WRITE_CONGESTION_OFF 9000
+
+
struct packet_settings
{
__u32 size; /* packet size in (512 byte) sectors */
@@ -271,6 +277,10 @@ struct pktcdvd_device

struct packet_iosched iosched;
struct gendisk *disk;
+
+ wait_queue_head_t write_congestion_wqueue;
+ int write_congestion_off;
+ int write_congestion_on;
};

#endif /* __KERNEL__ */