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: Hugh Dickins <[email protected]>
---
include/linux/sched.h | 42 ++++++++++++++++++++++++++++++++++++++----
mm/memory.c | 4 +++-
mm/rmap.c | 3 ++-
3 files changed, 43 insertions(+), 6 deletions(-)
--- mm7/include/linux/sched.h 2005-10-17 12:05:38.000000000 +0100
+++ mm8/include/linux/sched.h 2005-10-22 14:07:39.000000000 +0100
@@ -250,13 +250,47 @@ arch_get_unmapped_area_topdown(struct fi
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) \
@@ -267,8 +301,6 @@ extern void arch_unmap_area_topdown(stru
(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;
@@ -292,7 +324,9 @@ 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;
--- mm7/mm/memory.c 2005-10-22 14:07:25.000000000 +0100
+++ mm8/mm/memory.c 2005-10-22 14:07:40.000000000 +0100
@@ -372,7 +372,9 @@ copy_one_pte(struct mm_struct *dst_mm, s
/* 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);
}
}
--- mm7/mm/rmap.c 2005-10-22 14:07:25.000000000 +0100
+++ mm8/mm/rmap.c 2005-10-22 14:07:40.000000000 +0100
@@ -559,7 +559,8 @@ static int try_to_unmap_one(struct page
swap_duplicate(entry);
if (list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
- list_add(&mm->mmlist, &init_mm.mmlist);
+ if (list_empty(&mm->mmlist))
+ list_add(&mm->mmlist, &init_mm.mmlist);
spin_unlock(&mmlist_lock);
}
set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
-
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