1 files changed, 81 insertions, 7 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 65ab5c7067d9..c2b2a94f9d67 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -34,6 +34,7 @@
 #include <linux/swap.h>
 #include <linux/ksm.h>
 #include <linux/hash.h>
+#include <linux/freezer.h>
 
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -411,6 +412,20 @@ out:
         up_read(&mm->mmap_sem);
 }
 
+static struct page *page_trans_compound_anon(struct page *page)
+{
+        if (PageTransCompound(page)) {
+                struct page *head = compound_trans_head(page);
+                /*
+                 * head may actually be splitted and freed from under
+                 * us but it's ok here.
+                 */
+                if (PageAnon(head))
+                        return head;
+        }
+        return NULL;
+}
+
 static struct page *get_mergeable_page(struct rmap_item *rmap_item)
 {
         struct mm_struct *mm = rmap_item->mm;
@@ -430,7 +445,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
         page = follow_page(vma, addr, FOLL_GET);
         if (IS_ERR_OR_NULL(page))
                 goto out;
-        if (PageAnon(page)) {
+        if (PageAnon(page) || page_trans_compound_anon(page)) {
                 flush_anon_page(vma, page, addr);
                 flush_dcache_page(page);
         } else {
@@ -708,6 +723,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
         if (addr == -EFAULT)
                 goto out;
 
+        BUG_ON(PageTransCompound(page));
         ptep = page_check_address(page, mm, addr, &ptl, 0);
         if (!ptep)
                 goto out;
@@ -783,6 +799,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
                 goto out;
 
         pmd = pmd_offset(pud, addr);
+        BUG_ON(pmd_trans_huge(*pmd));
         if (!pmd_present(*pmd))
                 goto out;
 
@@ -800,6 +817,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
         set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
 
         page_remove_rmap(page);
+        if (!page_mapped(page))
+                try_to_free_swap(page);
         put_page(page);
 
         pte_unmap_unlock(ptep, ptl);
@@ -808,6 +827,33 @@ out:
         return err;
 }
 
+static int page_trans_compound_anon_split(struct page *page)
+{
+        int ret = 0;
+        struct page *transhuge_head = page_trans_compound_anon(page);
+        if (transhuge_head) {
+                /* Get the reference on the head to split it. */
+                if (get_page_unless_zero(transhuge_head)) {
+                        /*
+                         * Recheck we got the reference while the head
+                         * was still anonymous.
+                         */
+                        if (PageAnon(transhuge_head))
+                                ret = split_huge_page(transhuge_head);
+                        else
+                                /*
+                                 * Retry later if split_huge_page run
+                                 * from under us.
+                                 */
+                                ret = 1;
+                        put_page(transhuge_head);
+                } else
+                        /* Retry later if split_huge_page run from under us. */
+                        ret = 1;
+        }
+        return ret;
+}
+
 /*
  * try_to_merge_one_page - take two pages and merge them into one
  * @vma: the vma that holds the pte pointing to page
@@ -828,6 +874,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
 
         if (!(vma->vm_flags & VM_MERGEABLE))
                 goto out;
+        if (PageTransCompound(page) && page_trans_compound_anon_split(page))
+                goto out;
+        BUG_ON(PageTransCompound(page));
         if (!PageAnon(page))
                 goto out;
 
@@ -1247,6 +1296,18 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 
         slot = ksm_scan.mm_slot;
         if (slot == &ksm_mm_head) {
+                /*
+                 * A number of pages can hang around indefinitely on per-cpu
+                 * pagevecs, raised page count preventing write_protect_page
+                 * from merging them.  Though it doesn't really matter much,
+                 * it is puzzling to see some stuck in pages_volatile until
+                 * other activity jostles them out, and they also prevented
+                 * LTP's KSM test from succeeding deterministically; so drain
+                 * them here (here rather than on entry to ksm_do_scan(),
+                 * so we don't IPI too often when pages_to_scan is set low).
+                 */
+                lru_add_drain_all();
+
                 root_unstable_tree = RB_ROOT;
 
                 spin_lock(&ksm_mmlist_lock);
@@ -1277,7 +1338,13 @@ next_mm:
                         if (ksm_test_exit(mm))
                                 break;
                         *page = follow_page(vma, ksm_scan.address, FOLL_GET);
-                        if (!IS_ERR_OR_NULL(*page) && PageAnon(*page)) {
+                        if (IS_ERR_OR_NULL(*page)) {
+                                ksm_scan.address += PAGE_SIZE;
+                                cond_resched();
+                                continue;
+                        }
+                        if (PageAnon(*page) ||
+                            page_trans_compound_anon(*page)) {
                                 flush_anon_page(vma, *page, ksm_scan.address);
                                 flush_dcache_page(*page);
                                 rmap_item = get_next_rmap_item(slot,
@@ -1291,8 +1358,7 @@ next_mm:
                                 up_read(&mm->mmap_sem);
                                 return rmap_item;
                         }
-                        if (!IS_ERR_OR_NULL(*page))
-                                put_page(*page);
+                        put_page(*page);
                         ksm_scan.address += PAGE_SIZE;
                         cond_resched();
                 }
@@ -1352,7 +1418,7 @@ static void ksm_do_scan(unsigned int scan_npages)
         struct rmap_item *rmap_item;
         struct page *uninitialized_var(page);
 
-        while (scan_npages--) {
+        while (scan_npages-- && likely(!freezing(current))) {
                 cond_resched();
                 rmap_item = scan_get_next_rmap_item(&page);
                 if (!rmap_item)
@@ -1370,6 +1436,7 @@ static int ksmd_should_run(void)
 
 static int ksm_scan_thread(void *nothing)
 {
+        set_freezable();
         set_user_nice(current, 5);
 
         while (!kthread_should_stop()) {
@@ -1378,11 +1445,13 @@ static int ksm_scan_thread(void *nothing)
                         ksm_do_scan(ksm_thread_pages_to_scan);
                 mutex_unlock(&ksm_thread_mutex);
 
+                try_to_freeze();
+
                 if (ksmd_should_run()) {
                         schedule_timeout_interruptible(
                                 msecs_to_jiffies(ksm_thread_sleep_millisecs));
                 } else {
-                        wait_event_interruptible(ksm_thread_wait,
+                        wait_event_freezable(ksm_thread_wait,
                                 ksmd_should_run() || kthread_should_stop());
                 }
         }
@@ -1724,8 +1793,13 @@ static int ksm_memory_callback(struct notifier_block *self,
                 /*
                  * Keep it very simple for now: just lock out ksmd and
                  * MADV_UNMERGEABLE while any memory is going offline.
+                 * mutex_lock_nested() is necessary because lockdep was alarmed
+                 * that here we take ksm_thread_mutex inside notifier chain
+                 * mutex, and later take notifier chain mutex inside
+                 * ksm_thread_mutex to unlock it.   But that's safe because both
+                 * are inside mem_hotplug_mutex.
                  */
-                mutex_lock(&ksm_thread_mutex);
+                mutex_lock_nested(&ksm_thread_mutex, SINGLE_DEPTH_NESTING);
                 break;
 
         case MEM_OFFLINE: