Commit e519ce7a authored Sep 20, 2023 by Feng Tang Committed by Vlastimil Babka Oct 02, 2023

mm/slub: add sanity check for slub_min/max_order cmdline setup

Currently there are 2 parameters could be setup from kernel cmdline:
slub_min_order and slub_max_order. It's possible that the user
configured slub_min_order is bigger than the default slub_max_order
[1], which can still take effect, as calculate_oder() will use MAX_ORDER
as a fallback to check against, but has some downsides:

* the kernel message about SLUB will be strange in showing min/max
  orders:

    SLUB: HWalign=64, Order=9-3, MinObjects=0, CPUs=16, Nodes=1

* in calculate_order() called by each slab, the 2 loops of
  calc_slab_order() will all be meaningless due to slub_min_order
  is bigger than slub_max_order

* prevent future code cleanup like in [2].

Fix it by adding some sanity check to enforce the min/max semantics.

[1]. https://lore.kernel.org/lkml/21a0ba8b-bf05-0799-7c78-2a35f8c8d52a@os.amperecomputing.com/
[2]. https://lore.kernel.org/lkml/20230908145302.30320-7-vbabka@suse.cz/



Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

parent 8a749fd1

mm/slub.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -4711,6 +4711,9 @@ static int __init setup_slub_min_order(char *str)
		{
		get_option(&str, (int *)&slub_min_order);

		if (slub_min_order > slub_max_order)
		slub_max_order = slub_min_order;

		return 1;
		}

		@@ -4721,6 +4724,9 @@ static int __init setup_slub_max_order(char *str)
		get_option(&str, (int *)&slub_max_order);
		slub_max_order = min_t(unsigned int, slub_max_order, MAX_ORDER);

		if (slub_min_order > slub_max_order)
		slub_min_order = slub_max_order;

		return 1;
		}