[22/29] block: bdev_stack_limits wrapper

[Greg KH]

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Martin K. Petersen <martin.petersen@xxxxxxxxxx>

commit 17be8c245054b9c7786545af3ba3ca4e54cd4ad9 upstream.

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 <martin.petersen@xxxxxxxxxx>
Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Reviewed-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 block/blk-settings.c   |   22 ++++++++++++++++++++++
 include/linux/blkdev.h |    2 ++
 2 files changed, 24 insertions(+)

--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -560,6 +560,28 @@ int blk_stack_limits(struct queue_limits
 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)
  * @bdev:  the underlying block device (bottom)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -942,6 +942,8 @@ extern void blk_queue_io_opt(struct requ
 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);


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