Commit fad6551f authored Jul 31, 2025 by Christoph Hellwig Committed by Jens Axboe Jul 31, 2025

block: ensure discard_granularity is zero when discard is not supported



Documentation/ABI/stable/sysfs-block states:

  What: /sys/block/<disk>/queue/discard_granularity
  [...]
  A discard_granularity of 0 means that the device does not support
  discard functionality.

but this got broken when sorting out the block limits updates.  Fix this
by setting the discard_granularity limit to zero when the combined
max_discard_sectors is zero.

Fixes: 3c407dc7 ("block: default the discard granularity to sector size")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20250731152228.873923-1-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 76576185

block/blk-settings.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -400,12 +400,19 @@ int blk_validate_limits(struct queue_limits *lim)
		lim->max_discard_sectors =
		min(lim->max_hw_discard_sectors, lim->max_user_discard_sectors);

		/*
		* When discard is not supported, discard_granularity should be reported
		* as 0 to userspace.
		*/
		if (lim->max_discard_sectors)
		lim->discard_granularity =
		max(lim->discard_granularity, lim->physical_block_size);
		else
		lim->discard_granularity = 0;

		if (!lim->max_discard_segments)
		lim->max_discard_segments = 1;

		if (lim->discard_granularity < lim->physical_block_size)
		lim->discard_granularity = lim->physical_block_size;

		/*
		* By default there is no limit on the segment boundary alignment,
		* but if there is one it can't be smaller than the page size as