Commit 29383967 authored by Mike Kravetz's avatar Mike Kravetz Committed by Linus Torvalds
Browse files

hugetlb: add per-hstate mutex to synchronize user adjustments 

The helper routine hstate_next_node_to_alloc accesses and modifies the
hstate variable next_nid_to_alloc.  The helper is used by the routines
alloc_pool_huge_page and adjust_pool_surplus.  adjust_pool_surplus is
called with hugetlb_lock held.  However, alloc_pool_huge_page can not be
called with the hugetlb lock held as it will call the page allocator.
Two instances of alloc_pool_huge_page could be run in parallel or
alloc_pool_huge_page could run in parallel with adjust_pool_surplus
which may result in the variable next_nid_to_alloc becoming invalid for
the caller and pages being allocated on the wrong node.

Both alloc_pool_huge_page and adjust_pool_surplus are only called from
the routine set_max_huge_pages after boot.  set_max_huge_pages is only
called as the reusult of a user writing to the proc/sysfs nr_hugepages,
or nr_hugepages_mempolicy file to adjust the number of hugetlb pages.

It makes little sense to allow multiple adjustment to the number of
hugetlb pages in parallel.  Add a mutex to the hstate and use it to only
allow one hugetlb page adjustment at a time.  This will synchronize
modifications to the next_nid_to_alloc variable.

Link: https://lkml.kernel.org/r/20210409205254.242291-4-mike.kravetz@oracle.com


Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Reviewed-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 262443c0

include/linux/hugetlb.h

+1 −0
Original line number Diff line number Diff line
@@ -559,6 +559,7 @@ HPAGEFLAG(Freed, freed) 
#define HSTATE_NAME_LEN 32

/* Defines one hugetlb page size */

struct hstate {

	struct mutex resize_lock;

	int next_nid_to_alloc;

	int next_nid_to_free;

	unsigned int order;

mm/hugetlb.c

+8 −0
Original line number Diff line number Diff line
@@ -2621,6 +2621,11 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, 
	else

		return -ENOMEM;



	/*

	 * resize_lock mutex prevents concurrent adjustments to number of

	 * pages in hstate via the proc/sysfs interfaces.

	 */

	mutex_lock(&h->resize_lock);

	spin_lock(&hugetlb_lock);



	/*
@@ -2653,6 +2658,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, 
	if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {

		if (count > persistent_huge_pages(h)) {

			spin_unlock(&hugetlb_lock);

			mutex_unlock(&h->resize_lock);

			NODEMASK_FREE(node_alloc_noretry);

			return -EINVAL;

		}
@@ -2727,6 +2733,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, 
out:

	h->max_huge_pages = persistent_huge_pages(h);

	spin_unlock(&hugetlb_lock);

	mutex_unlock(&h->resize_lock);



	NODEMASK_FREE(node_alloc_noretry);
@@ -3214,6 +3221,7 @@ void __init hugetlb_add_hstate(unsigned int order) 
	BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);

	BUG_ON(order == 0);

	h = &hstates[hugetlb_max_hstate++];

	mutex_init(&h->resize_lock);

	h->order = order;

	h->mask = ~(huge_page_size(h) - 1);

	for (i = 0; i < MAX_NUMNODES; ++i)