[patch] max-sectors-2.6.9-rc1-bk14-A0

Ingo Molnar
2004-09-08T10:04:15Z

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this is a re-send of the max-sectors patch against 2.6.9-rc1-bk14.

the attached patch introduces two new /sys/block values:

/sys/block/*/queue/max_hw_sectors_kb
/sys/block/*/queue/max_sectors_kb

max_hw_sectors_kb is the maximum that the driver can handle and is
readonly. max_sectors_kb is the current max_sectors value and can be
tuned by root. PAGE_SIZE granularity is enforced.

It's all locking-safe and all affected layered drivers have been updated
as well. The patch has been in testing for a couple of weeks already as
part of the voluntary-preempt patches and it works just fine - people
use it to reduce IDE IRQ handling latencies. Please apply.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Ingo

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--- linux/include/linux/blkdev.h.orig
+++ linux/include/linux/blkdev.h
@@ -344,6 +344,7 @@ struct request_queue
unsigned int nr_congestion_off;

unsigned short max_sectors;
+ unsigned short max_hw_sectors;
unsigned short max_phys_segments;
unsigned short max_hw_segments;
unsigned short hardsect_size;
--- linux/drivers/block/ll_rw_blk.c.orig
+++ linux/drivers/block/ll_rw_blk.c
@@ -352,7 +352,7 @@ void blk_queue_max_sectors(request_queue
printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
}

- q->max_sectors = max_sectors;
+ q->max_sectors = q->max_hw_sectors = max_sectors;
}

EXPORT_SYMBOL(blk_queue_max_sectors);
@@ -454,7 +454,8 @@ EXPORT_SYMBOL(blk_queue_hardsect_size);
void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
{
/* zero is "infinity" */
- t->max_sectors = min_not_zero(t->max_sectors,b->max_sectors);
+ t->max_sectors = t->max_hw_sectors =
+ min_not_zero(t->max_sectors,b->max_sectors);

t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
@@ -2583,11 +2584,11 @@ end_io:
break;
}

- if (unlikely(bio_sectors(bio) > q->max_sectors)) {
+ if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
printk("bio too big device %s (%u > %u)\n",
bdevname(bio->bi_bdev, b),
bio_sectors(bio),
- q->max_sectors);
+ q->max_hw_sectors);
goto end_io;
}

@@ -3206,13 +3207,61 @@ queue_ra_store(struct request_queue *q,
unsigned long ra_kb;
ssize_t ret = queue_var_store(&ra_kb, page, count);

+ spin_lock_irq(q->queue_lock);
if (ra_kb > (q->max_sectors >> 1))
ra_kb = (q->max_sectors >> 1);

q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
+ spin_unlock_irq(q->queue_lock);
+
return ret;
}

+static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
+{
+ int max_sectors_kb = q->max_sectors >> 1;
+
+ return queue_var_show(max_sectors_kb, (page));
+}
+
+static ssize_t
+queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
+{
+ unsigned long max_sectors_kb,
+ max_hw_sectors_kb = q->max_hw_sectors >> 1,
+ page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
+ ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
+ int ra_kb;
+
+ if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
+ return -EINVAL;
+ /*
+ * Take the queue lock to update the readahead and max_sectors
+ * values synchronously:
+ */
+ spin_lock_irq(q->queue_lock);
+ /*
+ * Trim readahead window as well, if necessary:
+ */
+ ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
+ if (ra_kb > max_sectors_kb)
+ q->backing_dev_info.ra_pages =
+ max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
+
+ q->max_sectors = max_sectors_kb << 1;
+ spin_unlock_irq(q->queue_lock);
+
+ return ret;
+}
+
+static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
+{
+ int max_hw_sectors_kb = q->max_hw_sectors >> 1;
+
+ return queue_var_show(max_hw_sectors_kb, (page));
+}
+
+
static struct queue_sysfs_entry queue_requests_entry = {
.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
.show = queue_requests_show,
@@ -3225,9 +3274,22 @@ static struct queue_sysfs_entry queue_ra
.store = queue_ra_store,
};

+static struct queue_sysfs_entry queue_max_sectors_entry = {
+ .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_max_sectors_show,
+ .store = queue_max_sectors_store,
+};
+
+static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
+ .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
+ .show = queue_max_hw_sectors_show,
+};
+
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
+ &queue_max_hw_sectors_entry.attr,
+ &queue_max_sectors_entry.attr,
NULL,
};

--- linux/drivers/md/dm-table.c.orig
+++ linux/drivers/md/dm-table.c
@@ -825,7 +825,7 @@ void dm_table_set_restrictions(struct dm
* Make sure we obey the optimistic sub devices
* restrictions.
*/
- q->max_sectors = t->limits.max_sectors;
+ blk_queue_max_sectors(q, t->limits.max_sectors);
q->max_phys_segments = t->limits.max_phys_segments;
q->max_hw_segments = t->limits.max_hw_segments;
q->hardsect_size = t->limits.hardsect_size;
--- linux/drivers/md/linear.c.orig
+++ linux/drivers/md/linear.c
@@ -157,7 +157,7 @@ static int linear_run (mddev_t *mddev)
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

disk->size = rdev->size;
mddev->array_size += rdev->size;
--- linux/drivers/md/multipath.c.orig
+++ linux/drivers/md/multipath.c
@@ -325,7 +325,7 @@ static int multipath_add_disk(mddev_t *m
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

conf->working_disks++;
rdev->raid_disk = path;
@@ -479,7 +479,7 @@ static int multipath_run (mddev_t *mddev
* a merge_bvec_fn to be involved in multipath */
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

if (!rdev->faulty)
conf->working_disks++;
--- linux/drivers/md/raid0.c.orig
+++ linux/drivers/md/raid0.c
@@ -162,7 +162,7 @@ static int create_strip_zones (mddev_t *

if (rdev1->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

if (!smallest || (rdev1->size <smallest->size))
smallest = rdev1;
--- linux/drivers/md/raid1.c.orig
+++ linux/drivers/md/raid1.c
@@ -753,7 +753,7 @@ static int raid1_add_disk(mddev_t *mddev
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

p->head_position = 0;
rdev->raid_disk = mirror;
@@ -1196,7 +1196,7 @@ static int run(mddev_t *mddev)
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
- mddev->queue->max_sectors = (PAGE_SIZE>>9);
+ blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

disk->head_position = 0;
if (!rdev->faulty && rdev->in_sync)