block: Introduce helper to reset queue limits to default values

Commit Message

Martin K. Petersen June 12, 2009, 4:58 a.m. UTC

DM reuses the request queue when swapping in a new device table.
Introduce blk_set_default_limits() which can be used to reset the the
queue_limits prior to stacking devices.

Signed-off-by: Martin K. Petersen <[e-mail]>
Acked-by: Alasdair G Kergon <[e-mail]>

---


--
dm-devel mailing list
[e-mail]
https://www.redhat.com/mailman/listinfo/dm-devel

Comments

Mike Snitzer June 15, 2009, 2:56 p.m. UTC | #1

On Fri, Jun 12 2009 at 12:58am -0400,
Martin K. Petersen <[e-mail]> wrote:

> 
> DM reuses the request queue when swapping in a new device table.
> Introduce blk_set_default_limits() which can be used to reset the the
> queue_limits prior to stacking devices.
> 
> Signed-off-by: Martin K. Petersen <[e-mail]>
> Acked-by: Alasdair G Kergon <[e-mail]>

Jens,

Do you intend to provide this patch in your next push to Linus for
2.6.31?  I have a dependency on this patch for DM topology support.

Acked-by: Mike Snitzer <[e-mail]>

--
dm-devel mailing list
[e-mail]
https://www.redhat.com/mailman/listinfo/dm-devel

Jens Axboe June 15, 2009, 6:44 p.m. UTC | #2

On Mon, Jun 15 2009, Mike Snitzer wrote:
> On Fri, Jun 12 2009 at 12:58am -0400,
> Martin K. Petersen <[e-mail]> wrote:
> 
> > 
> > DM reuses the request queue when swapping in a new device table.
> > Introduce blk_set_default_limits() which can be used to reset the the
> > queue_limits prior to stacking devices.
> > 
> > Signed-off-by: Martin K. Petersen <[e-mail]>
> > Acked-by: Alasdair G Kergon <[e-mail]>
> 
> Jens,
> 
> Do you intend to provide this patch in your next push to Linus for
> 2.6.31?  I have a dependency on this patch for DM topology support.
> 
> Acked-by: Mike Snitzer <[e-mail]>

I'll add it for the next 2.6.31 push.

Patch

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 1c4df9b..35e9828 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -96,6 +96,31 @@  void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
 
 /**
+ * blk_set_default_limits - reset limits to default values
+ * @limits:  the queue_limits structure to reset
+ *
+ * Description:
+ *   Returns a queue_limit struct to its default state.  Can be used by
+ *   stacking drivers like DM that stage table swaps and reuse an
+ *   existing device queue.
+ */
+void blk_set_default_limits(struct queue_limits *lim)
+{
+	lim->max_phys_segments = MAX_PHYS_SEGMENTS;
+	lim->max_hw_segments = MAX_HW_SEGMENTS;
+	lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
+	lim->max_segment_size = MAX_SEGMENT_SIZE;
+	lim->max_sectors = lim->max_hw_sectors = SAFE_MAX_SECTORS;
+	lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
+	lim->bounce_pfn = BLK_BOUNCE_ANY;
+	lim->alignment_offset = 0;
+	lim->io_opt = 0;
+	lim->misaligned = 0;
+	lim->no_cluster = 0;
+}
+EXPORT_SYMBOL(blk_set_default_limits);
+
+/**
  * blk_queue_make_request - define an alternate make_request function for a device
  * @q:  the request queue for the device to be affected
  * @mfn: the alternate make_request function
@@ -123,18 +148,12 @@  void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 	 * set defaults
 	 */
 	q->nr_requests = BLKDEV_MAX_RQ;
-	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
-	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
-	blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
-	blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
 
 	q->make_request_fn = mfn;
 	q->backing_dev_info.ra_pages =
 			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 	q->backing_dev_info.state = 0;
 	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
-	blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
-	blk_queue_logical_block_size(q, 512);
 	blk_queue_dma_alignment(q, 511);
 	blk_queue_congestion_threshold(q);
 	q->nr_batching = BLK_BATCH_REQ;
@@ -147,6 +166,7 @@  void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 	q->unplug_timer.function = blk_unplug_timeout;
 	q->unplug_timer.data = (unsigned long)q;
 
+	blk_set_default_limits(&q->limits);
 	/*
 	 * by default assume old behaviour and bounce for any highmem page
 	 */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5e740a1..04bbc91 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -921,6 +921,7 @@  extern void blk_queue_alignment_offset(struct request_queue *q,
 				       unsigned int alignment);
 extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
 extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
+extern void blk_set_default_limits(struct queue_limits *lim);
 extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 			    sector_t offset);
 extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,