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Commit 4db0c3c2 authored by Jason Low's avatar Jason Low Committed by Linus Torvalds
Browse files

mm: remove rest of ACCESS_ONCE() usages 



We converted some of the usages of ACCESS_ONCE to READ_ONCE in the mm/
tree since it doesn't work reliably on non-scalar types.

This patch removes the rest of the usages of ACCESS_ONCE, and use the new
READ_ONCE API for the read accesses.  This makes things cleaner, instead
of using separate/multiple sets of APIs.

Signed-off-by: default avatarJason Low <jason.low2@hp.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarDavidlohr Bueso <dave@stgolabs.net>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Reviewed-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9d8c47e4

mm/huge_memory.c

+2 −2
Original line number Diff line number Diff line
@@ -183,7 +183,7 @@ static struct page *get_huge_zero_page(void) 
	struct page *zero_page;

retry:

	if (likely(atomic_inc_not_zero(&huge_zero_refcount)))

		return ACCESS_ONCE(huge_zero_page);

		return READ_ONCE(huge_zero_page);



	zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,

			HPAGE_PMD_ORDER);
@@ -202,7 +202,7 @@ static struct page *get_huge_zero_page(void) 
	/* We take additional reference here. It will be put back by shrinker */

	atomic_set(&huge_zero_refcount, 2);

	preempt_enable();

	return ACCESS_ONCE(huge_zero_page);

	return READ_ONCE(huge_zero_page);

}



static void put_huge_zero_page(void)

mm/internal.h

+2 −2
Original line number Diff line number Diff line
@@ -224,13 +224,13 @@ static inline unsigned long page_order(struct page *page) 
 * PageBuddy() should be checked first by the caller to minimize race window,

 * and invalid values must be handled gracefully.

 *

 * ACCESS_ONCE is used so that if the caller assigns the result into a local

 * READ_ONCE is used so that if the caller assigns the result into a local

 * variable and e.g. tests it for valid range before using, the compiler cannot

 * decide to remove the variable and inline the page_private(page) multiple

 * times, potentially observing different values in the tests and the actual

 * use of the result.

 */

#define page_order_unsafe(page)		ACCESS_ONCE(page_private(page))

#define page_order_unsafe(page)		READ_ONCE(page_private(page))



static inline bool is_cow_mapping(vm_flags_t flags)

{

mm/ksm.c

+5 −5
Original line number Diff line number Diff line
@@ -542,7 +542,7 @@ static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) 
	expected_mapping = (void *)stable_node +

				(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);

again:

	kpfn = ACCESS_ONCE(stable_node->kpfn);

	kpfn = READ_ONCE(stable_node->kpfn);

	page = pfn_to_page(kpfn);



	/*
@@ -551,7 +551,7 @@ static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) 
	 * but on Alpha we need to be more careful.

	 */

	smp_read_barrier_depends();

	if (ACCESS_ONCE(page->mapping) != expected_mapping)

	if (READ_ONCE(page->mapping) != expected_mapping)

		goto stale;



	/*
@@ -577,14 +577,14 @@ static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) 
		cpu_relax();

	}



	if (ACCESS_ONCE(page->mapping) != expected_mapping) {

	if (READ_ONCE(page->mapping) != expected_mapping) {

		put_page(page);

		goto stale;

	}



	if (lock_it) {

		lock_page(page);

		if (ACCESS_ONCE(page->mapping) != expected_mapping) {

		if (READ_ONCE(page->mapping) != expected_mapping) {

			unlock_page(page);

			put_page(page);

			goto stale;
@@ -600,7 +600,7 @@ static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) 
	 * before checking whether node->kpfn has been changed.

	 */

	smp_rmb();

	if (ACCESS_ONCE(stable_node->kpfn) != kpfn)

	if (READ_ONCE(stable_node->kpfn) != kpfn)

		goto again;

	remove_node_from_stable_tree(stable_node);

	return NULL;

mm/memcontrol.c

+9 −9
Original line number Diff line number Diff line
@@ -674,7 +674,7 @@ static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_zone *mz, 
static unsigned long soft_limit_excess(struct mem_cgroup *memcg)

{

	unsigned long nr_pages = page_counter_read(&memcg->memory);

	unsigned long soft_limit = ACCESS_ONCE(memcg->soft_limit);

	unsigned long soft_limit = READ_ONCE(memcg->soft_limit);

	unsigned long excess = 0;



	if (nr_pages > soft_limit)
@@ -1042,7 +1042,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, 
			goto out_unlock;



		do {

			pos = ACCESS_ONCE(iter->position);

			pos = READ_ONCE(iter->position);

			/*

			 * A racing update may change the position and

			 * put the last reference, hence css_tryget(),
@@ -1359,13 +1359,13 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg) 
	unsigned long limit;



	count = page_counter_read(&memcg->memory);

	limit = ACCESS_ONCE(memcg->memory.limit);

	limit = READ_ONCE(memcg->memory.limit);

	if (count < limit)

		margin = limit - count;



	if (do_swap_account) {

		count = page_counter_read(&memcg->memsw);

		limit = ACCESS_ONCE(memcg->memsw.limit);

		limit = READ_ONCE(memcg->memsw.limit);

		if (count <= limit)

			margin = min(margin, limit - count);

	}
@@ -2637,7 +2637,7 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep) 
		return cachep;



	memcg = get_mem_cgroup_from_mm(current->mm);

	kmemcg_id = ACCESS_ONCE(memcg->kmemcg_id);

	kmemcg_id = READ_ONCE(memcg->kmemcg_id);

	if (kmemcg_id < 0)

		goto out;
@@ -5007,7 +5007,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, 
	 * tunable will only affect upcoming migrations, not the current one.

	 * So we need to save it, and keep it going.

	 */

	move_flags = ACCESS_ONCE(memcg->move_charge_at_immigrate);

	move_flags = READ_ONCE(memcg->move_charge_at_immigrate);

	if (move_flags) {

		struct mm_struct *mm;

		struct mem_cgroup *from = mem_cgroup_from_task(p);
@@ -5241,7 +5241,7 @@ static u64 memory_current_read(struct cgroup_subsys_state *css, 
static int memory_low_show(struct seq_file *m, void *v)

{

	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

	unsigned long low = ACCESS_ONCE(memcg->low);

	unsigned long low = READ_ONCE(memcg->low);



	if (low == PAGE_COUNTER_MAX)

		seq_puts(m, "max\n");
@@ -5271,7 +5271,7 @@ static ssize_t memory_low_write(struct kernfs_open_file *of, 
static int memory_high_show(struct seq_file *m, void *v)

{

	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

	unsigned long high = ACCESS_ONCE(memcg->high);

	unsigned long high = READ_ONCE(memcg->high);



	if (high == PAGE_COUNTER_MAX)

		seq_puts(m, "max\n");
@@ -5301,7 +5301,7 @@ static ssize_t memory_high_write(struct kernfs_open_file *of, 
static int memory_max_show(struct seq_file *m, void *v)

{

	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

	unsigned long max = ACCESS_ONCE(memcg->memory.limit);

	unsigned long max = READ_ONCE(memcg->memory.limit);



	if (max == PAGE_COUNTER_MAX)

		seq_puts(m, "max\n");

mm/memory.c

+1 −1
Original line number Diff line number Diff line
@@ -2845,7 +2845,7 @@ static void do_fault_around(struct vm_area_struct *vma, unsigned long address, 
	struct vm_fault vmf;

	int off;



	nr_pages = ACCESS_ONCE(fault_around_bytes) >> PAGE_SHIFT;

	nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;

	mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;



	start_addr = max(address & mask, vma->vm_start);