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Message-ID: <1427150680.2515.36.camel@j-VirtualBox>
Date: Mon, 23 Mar 2015 15:44:40 -0700
From: Jason Low <jason.low2@...com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org, Jason Low <jason.low2@...com>
Cc: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Christoph Lameter <cl@...ux.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Aswin Chandramouleeswaran <aswin@...com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
Minchan Kim <minchan@...nel.org>,
Davidlohr Bueso <dave@...olabs.net>,
Rik van Riel <riel@...hat.com>
Subject: [PATCH] mm: Remove usages of ACCESS_ONCE
Commit 38c5ce936a08 converted ACCESS_ONCE usage in gup_pmd_range() to
READ_ONCE, since ACCESS_ONCE doesn't work reliably on non-scalar types.
This patch removes the rest of the usages of ACCESS_ONCE, and use
READ_ONCE for the read accesses. This also makes things cleaner,
instead of using separate/multiple sets of APIs.
Signed-off-by: Jason Low <jason.low2@...com>
---
mm/gup.c | 4 ++--
mm/huge_memory.c | 4 ++--
mm/internal.h | 4 ++--
mm/ksm.c | 10 +++++-----
mm/memcontrol.c | 18 +++++++++---------
mm/memory.c | 2 +-
mm/mmap.c | 8 ++++----
mm/page_alloc.c | 6 +++---
mm/rmap.c | 6 +++---
mm/slub.c | 4 ++--
mm/swap_state.c | 2 +-
mm/swapfile.c | 2 +-
12 files changed, 35 insertions(+), 35 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index ca7b607..6297f6b 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1019,7 +1019,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
*
* for an example see gup_get_pte in arch/x86/mm/gup.c
*/
- pte_t pte = ACCESS_ONCE(*ptep);
+ pte_t pte = READ_ONCE(*ptep);
struct page *page;
/*
@@ -1309,7 +1309,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
local_irq_save(flags);
pgdp = pgd_offset(mm, addr);
do {
- pgd_t pgd = ACCESS_ONCE(*pgdp);
+ pgd_t pgd = READ_ONCE(*pgdp);
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3412cc8..3ae874c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -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)
diff --git a/mm/internal.h b/mm/internal.h
index edaab69..a25e359 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -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)
{
diff --git a/mm/ksm.c b/mm/ksm.c
index 4162dce..7ee101e 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -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;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 74a9641..14c2f20 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -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");
diff --git a/mm/memory.c b/mm/memory.c
index 5ec794f..9f6d3c6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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);
diff --git a/mm/mmap.c b/mm/mmap.c
index 06a6076..e65cbe0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1b84950..ebffa0e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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)
diff --git a/mm/rmap.c b/mm/rmap.c
index 8030382..dad23a4 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -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
diff --git a/mm/slub.c b/mm/slub.c
index d01f912..3b5cb6b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -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)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 405923f..8bc8e66 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -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;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 63f55cc..a7e7210 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -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;
}
--
1.7.2.5
--
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