block: do not artificially constrain max_sectors for stacking drivers
Mike Snitzer [Wed, 1 Aug 2012 08:44:28 +0000 (10:44 +0200)]
blk_set_stacking_limits is intended to allow stacking drivers to build
up the limits of the stacked device based on the underlying devices'
limits.  But defaulting 'max_sectors' to BLK_DEF_MAX_SECTORS (1024)
doesn't allow the stacking driver to inherit a max_sectors larger than
1024 -- due to blk_stack_limits' use of min_not_zero.

It is now clear that this artificial limit is getting in the way so
change blk_set_stacking_limits's max_sectors to UINT_MAX (which allows
stacking drivers like dm-multipath to inherit 'max_sectors' from the
underlying paths).

Reported-by: Vijay Chauhan <vijay.chauhan@netapp.com>
Tested-by: Vijay Chauhan <vijay.chauhan@netapp.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

index d3234fc..565a678 100644 (file)
@@ -143,8 +143,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
        lim->discard_zeroes_data = 1;
        lim->max_segments = USHRT_MAX;
        lim->max_hw_sectors = UINT_MAX;
-
-       lim->max_sectors = BLK_DEF_MAX_SECTORS;
+       lim->max_sectors = UINT_MAX;
 }
 EXPORT_SYMBOL(blk_set_stacking_limits);