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Subject[PATCHv4 02/10] mm: convert mm->nr_ptes to atomic_t
Date
With split page table lock for PMD level we can't hold
mm->page_table_lock while updating nr_ptes.

Let's convert it to atomic_t to avoid races.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Alex Thorlton <athorlton@sgi.com>
---
fs/proc/task_mmu.c | 3 ++-
include/linux/mm_types.h | 2 +-
kernel/fork.c | 2 +-
mm/huge_memory.c | 10 +++++-----
mm/memory.c | 4 ++--
mm/mmap.c | 3 ++-
mm/oom_kill.c | 6 +++---
7 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7366e9d63c..c52c597fbf 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -62,7 +62,8 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
total_rss << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
mm->stack_vm << (PAGE_SHIFT-10), text, lib,
- (PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10,
+ (unsigned long) (PTRS_PER_PTE * sizeof(pte_t) *
+ atomic_read(&mm->nr_ptes)) >> 10,
swap << (PAGE_SHIFT-10));
}

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 84e0c56e1e..99f19e850d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -339,6 +339,7 @@ struct mm_struct {
pgd_t * pgd;
atomic_t mm_users; /* How many users with user space? */
atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
+ atomic_t nr_ptes; /* Page table pages */
int map_count; /* number of VMAs */

spinlock_t page_table_lock; /* Protects page tables and some counters */
@@ -360,7 +361,6 @@ struct mm_struct {
unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE */
unsigned long stack_vm; /* VM_GROWSUP/DOWN */
unsigned long def_flags;
- unsigned long nr_ptes; /* Page table pages */
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
unsigned long arg_start, arg_end, env_start, env_end;
diff --git a/kernel/fork.c b/kernel/fork.c
index 086fe73ad6..afe70530db 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -532,7 +532,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
mm->flags = (current->mm) ?
(current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
mm->core_state = NULL;
- mm->nr_ptes = 0;
+ atomic_set(&mm->nr_ptes, 0);
memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
spin_lock_init(&mm->page_table_lock);
mm_init_aio(mm);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 7489884682..bbd41a2f49 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -737,7 +737,7 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
- mm->nr_ptes++;
+ atomic_inc(&mm->nr_ptes);
spin_unlock(&mm->page_table_lock);
}

@@ -778,7 +778,7 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
entry = pmd_mkhuge(entry);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
- mm->nr_ptes++;
+ atomic_inc(&mm->nr_ptes);
return true;
}

@@ -903,7 +903,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd = pmd_mkold(pmd_wrprotect(pmd));
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
- dst_mm->nr_ptes++;
+ atomic_inc(&dst_mm->nr_ptes);

ret = 0;
out_unlock:
@@ -1358,7 +1358,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
if (is_huge_zero_pmd(orig_pmd)) {
- tlb->mm->nr_ptes--;
+ atomic_dec(&tlb->mm->nr_ptes);
spin_unlock(&tlb->mm->page_table_lock);
put_huge_zero_page();
} else {
@@ -1367,7 +1367,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
VM_BUG_ON(page_mapcount(page) < 0);
add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
VM_BUG_ON(!PageHead(page));
- tlb->mm->nr_ptes--;
+ atomic_dec(&tlb->mm->nr_ptes);
spin_unlock(&tlb->mm->page_table_lock);
tlb_remove_page(tlb, page);
}
diff --git a/mm/memory.c b/mm/memory.c
index ca00039471..1046396adf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -382,7 +382,7 @@ static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
pgtable_t token = pmd_pgtable(*pmd);
pmd_clear(pmd);
pte_free_tlb(tlb, token, addr);
- tlb->mm->nr_ptes--;
+ atomic_dec(&tlb->mm->nr_ptes);
}

static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
@@ -575,7 +575,7 @@ int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
spin_lock(&mm->page_table_lock);
wait_split_huge_page = 0;
if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
- mm->nr_ptes++;
+ atomic_inc(&mm->nr_ptes);
pmd_populate(mm, pmd, new);
new = NULL;
} else if (unlikely(pmd_trans_splitting(*pmd)))
diff --git a/mm/mmap.c b/mm/mmap.c
index 9d548512ff..1d0efbc974 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2726,7 +2726,8 @@ void exit_mmap(struct mm_struct *mm)
}
vm_unacct_memory(nr_accounted);

- WARN_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
+ WARN_ON(atomic_read(&mm->nr_ptes) >
+ (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
}

/* Insert vm structure into process list sorted by address
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 314e9d2743..7ab394e811 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -161,7 +161,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
* The baseline for the badness score is the proportion of RAM that each
* task's rss, pagetable and swap space use.
*/
- points = get_mm_rss(p->mm) + p->mm->nr_ptes +
+ points = get_mm_rss(p->mm) + atomic_read(&p->mm->nr_ptes) +
get_mm_counter(p->mm, MM_SWAPENTS);
task_unlock(p);

@@ -364,10 +364,10 @@ static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemas
continue;
}

- pr_info("[%5d] %5d %5d %8lu %8lu %7lu %8lu %5hd %s\n",
+ pr_info("[%5d] %5d %5d %8lu %8lu %7d %8lu %5hd %s\n",
task->pid, from_kuid(&init_user_ns, task_uid(task)),
task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
- task->mm->nr_ptes,
+ atomic_read(&task->mm->nr_ptes),
get_mm_counter(task->mm, MM_SWAPENTS),
task->signal->oom_score_adj, task->comm);
task_unlock(task);
--
1.8.4.rc3


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