All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH v2 0/2] mm: Remove usages of ACCESS_ONCE()
@ 2015-03-24 22:29 ` Jason Low
  0 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

v1->v2:
As suggested by Michal, we can split up the v1 patch into 2 patches.
 
The first patch addresses potentially incorrect usages of ACCESS_ONCE().
 
The second patch is more of a "cleanup" patch to convert the rest of
the ACCESS_ONCE() reads in mm/ to use the new READ_ONCE() API.
 
This makes it a bit easier to backport the fixes to older kernels.


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH v2 0/2] mm: Remove usages of ACCESS_ONCE()
@ 2015-03-24 22:29 ` Jason Low
  0 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

v1->v2:
As suggested by Michal, we can split up the v1 patch into 2 patches.
 
The first patch addresses potentially incorrect usages of ACCESS_ONCE().
 
The second patch is more of a "cleanup" patch to convert the rest of
the ACCESS_ONCE() reads in mm/ to use the new READ_ONCE() API.
 
This makes it a bit easier to backport the fixes to older kernels.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH v2 1/2] mm: Use READ_ONCE() for non-scalar types
  2015-03-24 22:29 ` Jason Low
@ 2015-03-24 22:29   ` Jason Low
  -1 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

Commit 38c5ce936a08 ("mm/gup: Replace ACCESS_ONCE with READ_ONCE")
converted ACCESS_ONCE usage in gup_pmd_range() to READ_ONCE, since
ACCESS_ONCE doesn't work reliably on non-scalar types.

This patch also fixes the other ACCESS_ONCE usages in gup_pte_range()
and __get_user_pages_fast() in mm/gup.c

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>
---
 mm/gup.c |    4 ++--
 1 files changed, 2 insertions(+), 2 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))
-- 
1.7.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 1/2] mm: Use READ_ONCE() for non-scalar types
@ 2015-03-24 22:29   ` Jason Low
  0 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

Commit 38c5ce936a08 ("mm/gup: Replace ACCESS_ONCE with READ_ONCE")
converted ACCESS_ONCE usage in gup_pmd_range() to READ_ONCE, since
ACCESS_ONCE doesn't work reliably on non-scalar types.

This patch also fixes the other ACCESS_ONCE usages in gup_pte_range()
and __get_user_pages_fast() in mm/gup.c

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>
---
 mm/gup.c |    4 ++--
 1 files changed, 2 insertions(+), 2 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))
-- 
1.7.1

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 2/2] mm: Remove rest of ACCESS_ONCE() usages
  2015-03-24 22:29 ` Jason Low
@ 2015-03-24 22:29   ` Jason Low
  -1 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

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>
---
 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 +-
 11 files changed, 33 insertions(+), 33 deletions(-)

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;
 	}
-- 
1.7.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 2/2] mm: Remove rest of ACCESS_ONCE() usages
@ 2015-03-24 22:29   ` Jason Low
  0 siblings, 0 replies; 6+ messages in thread
From: Jason Low @ 2015-03-24 22:29 UTC (permalink / raw)
  To: linux-mm, linux-kernel, cgroups, Jason Low
  Cc: Johannes Weiner, Michal Hocko, Christoph Lameter, Linus Torvalds,
	David Rientjes, Joonsoo Kim, Andrew Morton, Kirill A. Shutemov,
	Aswin Chandramouleeswaran, Christian Borntraeger, Mel Gorman,
	Hugh Dickins, Minchan Kim, Davidlohr Bueso, Rik van Riel

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>
---
 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 +-
 11 files changed, 33 insertions(+), 33 deletions(-)

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;
 	}
-- 
1.7.1

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-03-24 22:30 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-03-24 22:29 [PATCH v2 0/2] mm: Remove usages of ACCESS_ONCE() Jason Low
2015-03-24 22:29 ` Jason Low
2015-03-24 22:29 ` [PATCH v2 1/2] mm: Use READ_ONCE() for non-scalar types Jason Low
2015-03-24 22:29   ` Jason Low
2015-03-24 22:29 ` [PATCH v2 2/2] mm: Remove rest of ACCESS_ONCE() usages Jason Low
2015-03-24 22:29   ` Jason Low

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.