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mm: remove rest of ACCESS_ONCE() usages

Browse Source 
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: Jason Low <jason.low2@hp.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jason Low 2015-04-15 16:14:08 -07:00 committed by Linus Torvalds
parent 9d8c47e4bb
commit 4db0c3c298
11 changed files with 33 additions and 33 deletions
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4
mm/huge_memory.c
View File

@ -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 @@ retry:
/* 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)

4
mm/internal.h
View File

@ -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)
{

10
mm/ksm.c
View File

@ -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 @@ again:
* 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 @@ again:
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 @@ stale:
* 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;

18
mm/memcontrol.c
View File

@ -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");

2
mm/memory.c
View File

@ -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);

8
mm/mmap.c
View File

@ -1133,7 +1133,7 @@ static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *
* by another page fault trying to merge _that_. But that's ok: if it
* is being set up, that automatically means that it will be a singleton
* acceptable for merging, so we can do all of this optimistically. But
* we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
* we do that READ_ONCE() to make sure that we never re-load the pointer.
*
* IOW: that the "list_is_singular()" test on the anon_vma_chain only
* matters for the 'stable anon_vma' case (ie the thing we want to avoid
@ -1147,7 +1147,7 @@ static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *
static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
{
if (anon_vma_compatible(a, b)) {
struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
if (anon_vma && list_is_singular(&old->anon_vma_chain))
return anon_vma;
@ -2100,7 +2100,7 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
actual_size = size;
if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN)))
actual_size -= PAGE_SIZE;
if (actual_size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
if (actual_size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur))
return -ENOMEM;
/* mlock limit tests */
@ -2108,7 +2108,7 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
unsigned long locked;
unsigned long limit;
locked = mm->locked_vm + grow;
limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
limit = READ_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
limit >>= PAGE_SHIFT;
if (locked > limit && !capable(CAP_IPC_LOCK))
return -ENOMEM;

6
mm/page_alloc.c
View File

@ -1371,7 +1371,7 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
int to_drain, batch;
local_irq_save(flags);
batch = ACCESS_ONCE(pcp->batch);
batch = READ_ONCE(pcp->batch);
to_drain = min(pcp->count, batch);
if (to_drain > 0) {
free_pcppages_bulk(zone, to_drain, pcp);
@ -1570,7 +1570,7 @@ void free_hot_cold_page(struct page *page, bool cold)
list_add_tail(&page->lru, &pcp->lists[migratetype]);
pcp->count++;
if (pcp->count >= pcp->high) {
unsigned long batch = ACCESS_ONCE(pcp->batch);
unsigned long batch = READ_ONCE(pcp->batch);
free_pcppages_bulk(zone, batch, pcp);
pcp->count -= batch;
}
@ -6207,7 +6207,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
mask <<= (BITS_PER_LONG - bitidx - 1);
flags <<= (BITS_PER_LONG - bitidx - 1);
word = ACCESS_ONCE(bitmap[word_bitidx]);
word = READ_ONCE(bitmap[word_bitidx]);
for (;;) {
old_word = cmpxchg(&bitmap[word_bitidx], word, (word & ~mask) | flags);
if (word == old_word)

6
mm/rmap.c
View File

@ -456,7 +456,7 @@ struct anon_vma *page_get_anon_vma(struct page *page)
unsigned long anon_mapping;
rcu_read_lock();
anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
anon_mapping = (unsigned long)READ_ONCE(page->mapping);
if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
goto out;
if (!page_mapped(page))
@ -500,14 +500,14 @@ struct anon_vma *page_lock_anon_vma_read(struct page *page)
unsigned long anon_mapping;
rcu_read_lock();
anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
anon_mapping = (unsigned long)READ_ONCE(page->mapping);
if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
goto out;
if (!page_mapped(page))
goto out;
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
root_anon_vma = ACCESS_ONCE(anon_vma->root);
root_anon_vma = READ_ONCE(anon_vma->root);
if (down_read_trylock(&root_anon_vma->rwsem)) {
/*
* If the page is still mapped, then this anon_vma is still

4
mm/slub.c
View File

@ -4277,7 +4277,7 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
int node;
struct page *page;
page = ACCESS_ONCE(c->page);
page = READ_ONCE(c->page);
if (!page)
continue;
@ -4292,7 +4292,7 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
total += x;
nodes[node] += x;
page = ACCESS_ONCE(c->partial);
page = READ_ONCE(c->partial);
if (page) {
node = page_to_nid(page);
if (flags & SO_TOTAL)

2
mm/swap_state.c
View File

@ -390,7 +390,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
unsigned int pages, max_pages, last_ra;
static atomic_t last_readahead_pages;
max_pages = 1 << ACCESS_ONCE(page_cluster);
max_pages = 1 << READ_ONCE(page_cluster);
if (max_pages <= 1)
return 1;

2
mm/swapfile.c
View File

@ -1312,7 +1312,7 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
else
continue;
}
count = ACCESS_ONCE(si->swap_map[i]);
count = READ_ONCE(si->swap_map[i]);
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
}