block: bdev_stack_limits wrapper

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@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 66d4aa8799b7517de258e3e334a69372154580a9..d5aa8865c6441d80e9b5792c2ac7bd63a52debd2 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -559,6 +559,28 @@ 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
index adf99c617cd3e54d7725a3e1d7c54cdddb30db4d..912b8ff3f27290d333fa8f7d4f11626817a42ea2 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -942,6 +942,8 @@ 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);