#define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */
#define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */
#define STABLE_FLAG 0x200 /* is listed from the stable tree */
+#define KSM_FLAG_MASK (SEQNR_MASK|UNSTABLE_FLAG|STABLE_FLAG)
+ /* to mask all the flags */
/* The stable and unstable tree heads */
static struct rb_root one_stable_tree[1] = { RB_ROOT };
} else {
newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage),
vma->vm_page_prot));
+ /*
+ * We're replacing an anonymous page with a zero page, which is
+ * not anonymous. We need to do proper accounting otherwise we
+ * will get wrong values in /proc, and a BUG message in dmesg
+ * when tearing down the mm.
+ */
+ dec_mm_counter(mm, MM_ANONPAGES);
}
flush_cache_page(vma, addr, pte_pfn(*ptep));
tree_rmap_item =
unstable_tree_search_insert(rmap_item, page, &tree_page);
if (tree_rmap_item) {
+ bool split;
+
kpage = try_to_merge_two_pages(rmap_item, page,
tree_rmap_item, tree_page);
+ /*
+ * If both pages we tried to merge belong to the same compound
+ * page, then we actually ended up increasing the reference
+ * count of the same compound page twice, and split_huge_page
+ * failed.
+ * Here we set a flag if that happened, and we use it later to
+ * try split_huge_page again. Since we call put_page right
+ * afterwards, the reference count will be correct and
+ * split_huge_page should succeed.
+ */
+ split = PageTransCompound(page)
+ && compound_head(page) == compound_head(tree_page);
put_page(tree_page);
if (kpage) {
/*
break_cow(tree_rmap_item);
break_cow(rmap_item);
}
+ } else if (split) {
+ /*
+ * We are here if we tried to merge two pages and
+ * failed because they both belonged to the same
+ * compound page. We will split the page now, but no
+ * merging will take place.
+ * We do not want to add the cost of a full lock; if
+ * the page is locked, it is better to skip it and
+ * perhaps try again later.
+ */
+ if (!trylock_page(page))
+ return;
+ split_huge_page(page);
+ unlock_page(page);
}
}
}
try_to_freeze();
if (ksmd_should_run()) {
- schedule_timeout_interruptible(
- msecs_to_jiffies(ksm_thread_sleep_millisecs));
+ if (ksm_thread_sleep_millisecs >= 1000)
+ schedule_timeout_interruptible(
+ msecs_to_jiffies(round_jiffies_relative(ksm_thread_sleep_millisecs)));
+ else
+ schedule_timeout_interruptible(
+ msecs_to_jiffies(ksm_thread_sleep_millisecs));
} else {
wait_event_freezable(ksm_thread_wait,
ksmd_should_run() || kthread_should_stop());
anon_vma_lock_read(anon_vma);
anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
0, ULONG_MAX) {
+ unsigned long addr;
+
cond_resched();
vma = vmac->vma;
- if (rmap_item->address < vma->vm_start ||
- rmap_item->address >= vma->vm_end)
+
+ /* Ignore the stable/unstable/sqnr flags */
+ addr = rmap_item->address & ~KSM_FLAG_MASK;
+
+ if (addr < vma->vm_start || addr >= vma->vm_end)
continue;
/*
* Initially we examine only the vma which covers this
if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
continue;
- if (!rwc->rmap_one(page, vma,
- rmap_item->address, rwc->arg)) {
+ if (!rwc->rmap_one(page, vma, addr, rwc->arg)) {
anon_vma_unlock_read(anon_vma);
return;
}