block: bdev_stack_limits wrapper

DM does not want to know about partition offsets. Add a partition-aware wrapper that DM can use when stacking block devices. Signed-off-by: Martin K. Petersen <[email protected]> Acked-by: Mike Snitzer <[email protected]> Reviewed-by: Alasdair G Kergon <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
vbatts · Jan 11, 2010 · 17be8c2 · 17be8c2
1 parent dd3d145
commit 17be8c2
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diff --git a/block/blk-settings.c b/block/blk-settings.c
@@ -639,6 +639,28 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 }
 EXPORT_SYMBOL(blk_stack_limits);
 
+/**
+ * bdev_stack_limits - adjust queue limits for stacked drivers
+ * @t:	the stacking driver limits (top device)
+ * @bdev:  the component block_device (bottom)
+ * @start:  first data sector within component device
+ *
+ * Description:
+ *    Merges queue limits for a top device and a block_device.  Returns
+ *    0 if alignment didn't change.  Returns -1 if adding the bottom
+ *    device caused misalignment.
+ */
+int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
+		      sector_t start)
+{
+	struct request_queue *bq = bdev_get_queue(bdev);
+
+	start += get_start_sect(bdev);
+
+	return blk_stack_limits(t, &bq->limits, start << 9);
+}
+EXPORT_SYMBOL(bdev_stack_limits);
+
 /**
  * disk_stack_limits - adjust queue limits for stacked drivers
  * @disk:  MD/DM gendisk (top)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
@@ -938,6 +938,8 @@ 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 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
+			    sector_t offset);
 extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
 			      sector_t offset);
 extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);