[PATCHv6 16/36] mm, thp: remove compound_lock

Kirill A. Shutemov
2015-06-03T17:19:17Z

We are going to use migration entries to stabilize page counts. It means
we don't need compound_lock() for that.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
include/linux/mm.h | 35 -----------------------------------
include/linux/page-flags.h | 12 +-----------
mm/debug.c | 3 ---
mm/memcontrol.c | 11 +++--------
4 files changed, 4 insertions(+), 57 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f079d9ffc797..31cd5be081cf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -403,41 +403,6 @@ static inline int is_vmalloc_or_module_addr(const void *x)

extern void kvfree(const void *addr);

-static inline void compound_lock(struct page *page)
-{
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- VM_BUG_ON_PAGE(PageSlab(page), page);
- bit_spin_lock(PG_compound_lock, &page->flags);
-#endif
-}
-
-static inline void compound_unlock(struct page *page)
-{
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- VM_BUG_ON_PAGE(PageSlab(page), page);
- bit_spin_unlock(PG_compound_lock, &page->flags);
-#endif
-}
-
-static inline unsigned long compound_lock_irqsave(struct page *page)
-{
- unsigned long uninitialized_var(flags);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- local_irq_save(flags);
- compound_lock(page);
-#endif
- return flags;
-}
-
-static inline void compound_unlock_irqrestore(struct page *page,
- unsigned long flags)
-{
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- compound_unlock(page);
- local_irq_restore(flags);
-#endif
-}
-
/*
* The atomic page->_mapcount, starts from -1: so that transitions
* both from it and to it can be tracked, using atomic_inc_and_test
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 91b7f9b2b774..74b7cece1dfa 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -106,9 +106,6 @@ enum pageflags {
#ifdef CONFIG_MEMORY_FAILURE
PG_hwpoison, /* hardware poisoned page. Don't touch */
#endif
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- PG_compound_lock,
-#endif
__NR_PAGEFLAGS,

/* Filesystems */
@@ -683,12 +680,6 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
#define __PG_MLOCKED 0
#endif

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define __PG_COMPOUND_LOCK (1 << PG_compound_lock)
-#else
-#define __PG_COMPOUND_LOCK 0
-#endif
-
/*
* Flags checked when a page is freed. Pages being freed should not have
* these flags set. It they are, there is a problem.
@@ -698,8 +689,7 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
1 << PG_private | 1 << PG_private_2 | \
1 << PG_writeback | 1 << PG_reserved | \
1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
- 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
- __PG_COMPOUND_LOCK)
+ 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON )

/*
* Flags checked when a page is prepped for return by the page allocator.
diff --git a/mm/debug.c b/mm/debug.c
index 3eb3ac2fcee7..9dfcd77e7354 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -45,9 +45,6 @@ static const struct trace_print_flags pageflag_names[] = {
#ifdef CONFIG_MEMORY_FAILURE
{1UL << PG_hwpoison, "hwpoison" },
#endif
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- {1UL << PG_compound_lock, "compound_lock" },
-#endif
};

static void dump_flags(unsigned long flags,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1c7c6bb69d3c..d0d862e4ca74 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2761,9 +2761,7 @@ struct mem_cgroup *__mem_cgroup_from_kmem(void *ptr)

/*
* Because tail pages are not marked as "used", set it. We're under
- * zone->lru_lock, 'splitting on pmd' and compound_lock.
- * charge/uncharge will be never happen and move_account() is done under
- * compound_lock(), so we don't have to take care of races.
+ * zone->lru_lock and migration entries setup in all page mappings.
*/
void mem_cgroup_split_huge_fixup(struct page *head)
{
@@ -4738,9 +4736,7 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
* @from: mem_cgroup which the page is moved from.
* @to: mem_cgroup which the page is moved to. @from != @to.
*
- * The caller must confirm following.
- * - page is not on LRU (isolate_page() is useful.)
- * - compound_lock is held when nr_pages > 1
+ * The caller must make sure the page is not on LRU (isolate_page() is useful.)
*
* This function doesn't do "charge" to new cgroup and doesn't do "uncharge"
* from old cgroup.
@@ -5061,8 +5057,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
struct page *page;

/*
- * We don't take compound_lock() here but no race with splitting thp
- * happens because:
+ * No race with splitting thp happens because:
* - if pmd_trans_huge_lock() returns 1, the relevant thp is not
* under splitting, which means there's no concurrent thp split,
* - if another thread runs into split_huge_page() just after we
--
2.1.4