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block: do not artificially constrain max_sectors for stacking drivers

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 <>
Tested-by: Vijay Chauhan <>
Signed-off-by: Mike Snitzer <>
Signed-off-by: Jens Axboe <>
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1 parent a051661 commit fe86cdcef73ba19a2246a124f0ddbd19b14fb549 @snitm snitm committed with axboe Aug 1, 2012
Showing with 1 addition and 2 deletions.
  1. +1 −2 block/blk-settings.c
@@ -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;

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