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Commit f412ac08 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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[PATCH] mm: fix rss and mmlist locking 



A couple of oddities were guarded by page_table_lock, no longer properly
guarded when that is split.

The mm_counters of file_rss and anon_rss: make those an atomic_t, or an
atomic64_t if the architecture supports it, in such a case.  Definitions by
courtesy of Christoph Lameter: who spent considerable effort on more scalable
ways of counting, but found insufficient benefit in practice.

And adding an mm with swap to the mmlist for swapoff: the list is well-
guarded by its own lock, but the list_empty check now has to be repeated
inside it.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4c21e2f2

include/linux/sched.h

+38 −4
Original line number Diff line number Diff line
@@ -249,13 +249,47 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 
extern void arch_unmap_area(struct mm_struct *, unsigned long);

extern void arch_unmap_area_topdown(struct mm_struct *, unsigned long);



#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS

/*

 * The mm counters are not protected by its page_table_lock,

 * so must be incremented atomically.

 */

#ifdef ATOMIC64_INIT

#define set_mm_counter(mm, member, value) atomic64_set(&(mm)->_##member, value)

#define get_mm_counter(mm, member) ((unsigned long)atomic64_read(&(mm)->_##member))

#define add_mm_counter(mm, member, value) atomic64_add(value, &(mm)->_##member)

#define inc_mm_counter(mm, member) atomic64_inc(&(mm)->_##member)

#define dec_mm_counter(mm, member) atomic64_dec(&(mm)->_##member)

typedef atomic64_t mm_counter_t;

#else /* !ATOMIC64_INIT */

/*

 * The counters wrap back to 0 at 2^32 * PAGE_SIZE,

 * that is, at 16TB if using 4kB page size.

 */

#define set_mm_counter(mm, member, value) atomic_set(&(mm)->_##member, value)

#define get_mm_counter(mm, member) ((unsigned long)atomic_read(&(mm)->_##member))

#define add_mm_counter(mm, member, value) atomic_add(value, &(mm)->_##member)

#define inc_mm_counter(mm, member) atomic_inc(&(mm)->_##member)

#define dec_mm_counter(mm, member) atomic_dec(&(mm)->_##member)

typedef atomic_t mm_counter_t;

#endif /* !ATOMIC64_INIT */



#else  /* NR_CPUS < CONFIG_SPLIT_PTLOCK_CPUS */

/*

 * The mm counters are protected by its page_table_lock,

 * so can be incremented directly.

 */

#define set_mm_counter(mm, member, value) (mm)->_##member = (value)

#define get_mm_counter(mm, member) ((mm)->_##member)

#define add_mm_counter(mm, member, value) (mm)->_##member += (value)

#define inc_mm_counter(mm, member) (mm)->_##member++

#define dec_mm_counter(mm, member) (mm)->_##member--

#define get_mm_rss(mm) ((mm)->_file_rss + (mm)->_anon_rss)

typedef unsigned long mm_counter_t;



#endif /* NR_CPUS < CONFIG_SPLIT_PTLOCK_CPUS */



#define get_mm_rss(mm)					\

	(get_mm_counter(mm, file_rss) + get_mm_counter(mm, anon_rss))

#define update_hiwater_rss(mm)	do {			\

	unsigned long _rss = get_mm_rss(mm);		\

	if ((mm)->hiwater_rss < _rss)			\
@@ -266,8 +300,6 @@ extern void arch_unmap_area_topdown(struct mm_struct *, unsigned long); 
		(mm)->hiwater_vm = (mm)->total_vm;	\

} while (0)



typedef unsigned long mm_counter_t;



struct mm_struct {

	struct vm_area_struct * mmap;		/* list of VMAs */

	struct rb_root mm_rb;
@@ -291,7 +323,9 @@ struct mm_struct { 
						 * by mmlist_lock

						 */



	/* Special counters protected by the page_table_lock */

	/* Special counters, in some configurations protected by the

	 * page_table_lock, in other configurations by being atomic.

	 */

	mm_counter_t _file_rss;

	mm_counter_t _anon_rss;

mm/memory.c

+3 −1
Original line number Diff line number Diff line
@@ -372,7 +372,9 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, 
			/* make sure dst_mm is on swapoff's mmlist. */

			if (unlikely(list_empty(&dst_mm->mmlist))) {

				spin_lock(&mmlist_lock);

				list_add(&dst_mm->mmlist, &src_mm->mmlist);

				if (list_empty(&dst_mm->mmlist))

					list_add(&dst_mm->mmlist,

						 &src_mm->mmlist);

				spin_unlock(&mmlist_lock);

			}

		}

mm/rmap.c

+2 −1
Original line number Diff line number Diff line
@@ -559,6 +559,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma) 
		swap_duplicate(entry);

		if (list_empty(&mm->mmlist)) {

			spin_lock(&mmlist_lock);

			if (list_empty(&mm->mmlist))

				list_add(&mm->mmlist, &init_mm.mmlist);

			spin_unlock(&mmlist_lock);

		}