Use sk_set_memalloc() on the nbd socket.
Limit each request to 1 page, so that the request throttling also limits the
number of in-flight pages and force the IO scheduler to NOOP as anything else
doesn't make sense anyway.
Signed-off-by: Peter Zijlstra <[email protected]>
Signed-off-by: Daniel Phillips <[email protected]>
---
block/elevator.c | 5 +++++
block/ll_rw_blk.c | 12 ++++++++++--
drivers/block/nbd.c | 12 +++++++++++-
include/linux/blkdev.h | 9 +++++++++
4 files changed, 35 insertions(+), 3 deletions(-)
Index: linux-2.6/block/ll_rw_blk.c
===================================================================
--- linux-2.6.orig/block/ll_rw_blk.c 2006-08-12 15:38:01.000000000 +0200
+++ linux-2.6/block/ll_rw_blk.c 2006-08-12 15:38:11.000000000 +0200
@@ -1899,6 +1899,14 @@ EXPORT_SYMBOL(blk_init_queue);
request_queue_t *
blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
{
+ return blk_init_queue_node_elv(rfn, lock, node_id, NULL);
+}
+EXPORT_SYMBOL(blk_init_queue_node);
+
+request_queue_t *
+blk_init_queue_node_elv(request_fn_proc *rfn, spinlock_t *lock, int node_id,
+ char *elv_name)
+{
request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
if (!q)
@@ -1939,7 +1947,7 @@ blk_init_queue_node(request_fn_proc *rfn
/*
* all done
*/
- if (!elevator_init(q, NULL)) {
+ if (!elevator_init(q, elv_name)) {
blk_queue_congestion_threshold(q);
return q;
}
@@ -1947,7 +1955,7 @@ blk_init_queue_node(request_fn_proc *rfn
blk_put_queue(q);
return NULL;
}
-EXPORT_SYMBOL(blk_init_queue_node);
+EXPORT_SYMBOL(blk_init_queue_node_elv);
int blk_get_queue(request_queue_t *q)
{
Index: linux-2.6/drivers/block/nbd.c
===================================================================
--- linux-2.6.orig/drivers/block/nbd.c 2006-08-12 15:38:01.000000000 +0200
+++ linux-2.6/drivers/block/nbd.c 2006-08-12 15:50:33.000000000 +0200
@@ -361,8 +361,13 @@ static void nbd_do_it(struct nbd_device
BUG_ON(lo->magic != LO_MAGIC);
+ if (sk_set_memalloc(lo->sock->sk))
+ printk(KERN_WARNING
+ "failed to set SO_MEMALLOC on NBD socket\n");
+
while ((req = nbd_read_stat(lo)) != NULL)
nbd_end_request(req);
+
return;
}
@@ -628,11 +633,16 @@ static int __init nbd_init(void)
* every gendisk to have its very own request_queue struct.
* These structs are big so we dynamically allocate them.
*/
- disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
+ disk->queue = blk_init_queue_node_elv(do_nbd_request,
+ &nbd_lock, -1, "noop");
if (!disk->queue) {
put_disk(disk);
goto out;
}
+ blk_queue_pin_elevator(disk->queue);
+ blk_queue_max_segment_size(disk->queue, PAGE_SIZE);
+ blk_queue_max_hw_segments(disk->queue, 1);
+ blk_queue_max_phys_segments(disk->queue, 1);
}
if (register_blkdev(NBD_MAJOR, "nbd")) {
Index: linux-2.6/include/linux/blkdev.h
===================================================================
--- linux-2.6.orig/include/linux/blkdev.h 2006-08-12 15:38:01.000000000 +0200
+++ linux-2.6/include/linux/blkdev.h 2006-08-12 15:38:11.000000000 +0200
@@ -444,6 +444,12 @@ struct request_queue
#define QUEUE_FLAG_REENTER 6 /* Re-entrancy avoidance */
#define QUEUE_FLAG_PLUGGED 7 /* queue is plugged */
#define QUEUE_FLAG_ELVSWITCH 8 /* don't use elevator, just do FIFO */
+#define QUEUE_FLAG_ELVPINNED 9 /* pin the current elevator */
+
+static inline void blk_queue_pin_elevator(struct request_queue *q)
+{
+ set_bit(QUEUE_FLAG_ELVPINNED, &q->queue_flags);
+}
enum {
/*
@@ -696,6 +702,9 @@ static inline void elv_dispatch_add_tail
/*
* Access functions for manipulating queue properties
*/
+extern request_queue_t *blk_init_queue_node_elv(request_fn_proc *rfn,
+ spinlock_t *lock, int node_id,
+ char *elv_name);
extern request_queue_t *blk_init_queue_node(request_fn_proc *rfn,
spinlock_t *lock, int node_id);
extern request_queue_t *blk_init_queue(request_fn_proc *, spinlock_t *);
Index: linux-2.6/block/elevator.c
===================================================================
--- linux-2.6.orig/block/elevator.c 2006-08-12 15:38:01.000000000 +0200
+++ linux-2.6/block/elevator.c 2006-08-12 15:38:11.000000000 +0200
@@ -861,6 +861,11 @@ ssize_t elv_iosched_store(request_queue_
size_t len;
struct elevator_type *e;
+ if (test_bit(QUEUE_FLAG_ELVPINNED, &q->queue_flags)) {
+ printk(KERN_ERR "elevator: cannot switch elevator, pinned\n");
+ return count;
+ }
+
elevator_name[sizeof(elevator_name) - 1] = '\0';
strncpy(elevator_name, name, sizeof(elevator_name) - 1);
len = strlen(elevator_name);
-
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