1 files changed, 276 insertions, 22 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index b68c93014f50..05b6803f0cce 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -37,6 +37,25 @@ static const struct address_space_operations swap_aops = {
 
 struct address_space *swapper_spaces[MAX_SWAPFILES];
 static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
+bool swap_vma_readahead = true;
+
+#define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
+#define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
+#define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
+#define SWAP_RA_WIN_MASK	(~PAGE_MASK & ~SWAP_RA_HITS_MASK)
+
+#define SWAP_RA_HITS(v)		((v) & SWAP_RA_HITS_MASK)
+#define SWAP_RA_WIN(v)		(((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
+#define SWAP_RA_ADDR(v)		((v) & PAGE_MASK)
+
+#define SWAP_RA_VAL(addr, win, hits)				\
+	(((addr) & PAGE_MASK) |					\
+	 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) |	\
+	 ((hits) & SWAP_RA_HITS_MASK))
+
+/* Initial readahead hits is 4 to start up with a small window */
+#define GET_SWAP_RA_VAL(vma)					\
+	(atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
 
 #define INC_CACHE_INFO(x)	do { swap_cache_info.x++; } while (0)
 #define ADD_CACHE_INFO(x, nr)	do { swap_cache_info.x += (nr); } while (0)
@@ -219,6 +238,17 @@ int add_to_swap(struct page *page)
 		 * clear SWAP_HAS_CACHE flag.
 		 */
 		goto fail;
+	/*
+	 * Normally the page will be dirtied in unmap because its pte should be
+	 * dirty. A special case is MADV_FREE page. The page'e pte could have
+	 * dirty bit cleared but the page's SwapBacked bit is still set because
+	 * clearing the dirty bit and SwapBacked bit has no lock protected. For
+	 * such page, unmap will not set dirty bit for it, so page reclaim will
+	 * not write the page out. This can cause data corruption when the page
+	 * is swap in later. Always setting the dirty bit for the page solves
+	 * the problem.
+	 */
+	set_page_dirty(page);
 
 	return 1;
 
@@ -297,19 +327,36 @@ void free_pages_and_swap_cache(struct page **pages, int nr)
  * lock getting page table operations atomic even if we drop the page
  * lock before returning.
  */
-struct page * lookup_swap_cache(swp_entry_t entry)
+struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
+			       unsigned long addr)
 {
 	struct page *page;
+	unsigned long ra_info;
+	int win, hits, readahead;
 
 	page = find_get_page(swap_address_space(entry), swp_offset(entry));
 
-	if (page && likely(!PageTransCompound(page))) {
+	INC_CACHE_INFO(find_total);
+	if (page) {
 		INC_CACHE_INFO(find_success);
-		if (TestClearPageReadahead(page))
-			atomic_inc(&swapin_readahead_hits);
+		if (unlikely(PageTransCompound(page)))
+			return page;
+		readahead = TestClearPageReadahead(page);
+		if (vma) {
+			ra_info = GET_SWAP_RA_VAL(vma);
+			win = SWAP_RA_WIN(ra_info);
+			hits = SWAP_RA_HITS(ra_info);
+			if (readahead)
+				hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
+			atomic_long_set(&vma->swap_readahead_info,
+					SWAP_RA_VAL(addr, win, hits));
+		}
+		if (readahead) {
+			count_vm_event(SWAP_RA_HIT);
+			if (!vma)
+				atomic_inc(&swapin_readahead_hits);
+		}
 	}
-
-	INC_CACHE_INFO(find_total);
 	return page;
 }
 
@@ -424,22 +471,20 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	return retpage;
 }
 
-static unsigned long swapin_nr_pages(unsigned long offset)
+static unsigned int __swapin_nr_pages(unsigned long prev_offset,
+				      unsigned long offset,
+				      int hits,
+				      int max_pages,
+				      int prev_win)
 {
-	static unsigned long prev_offset;
-	unsigned int pages, max_pages, last_ra;
-	static atomic_t last_readahead_pages;
-
-	max_pages = 1 << READ_ONCE(page_cluster);
-	if (max_pages <= 1)
-		return 1;
+	unsigned int pages, last_ra;
 
 	/*
 	 * This heuristic has been found to work well on both sequential and
 	 * random loads, swapping to hard disk or to SSD: please don't ask
 	 * what the "+ 2" means, it just happens to work well, that's all.
 	 */
-	pages = atomic_xchg(&swapin_readahead_hits, 0) + 2;
+	pages = hits + 2;
 	if (pages == 2) {
 		/*
 		 * We can have no readahead hits to judge by: but must not get
@@ -448,7 +493,6 @@ static unsigned long swapin_nr_pages(unsigned long offset)
 		 */
 		if (offset != prev_offset + 1 && offset != prev_offset - 1)
 			pages = 1;
-		prev_offset = offset;
 	} else {
 		unsigned int roundup = 4;
 		while (roundup < pages)
@@ -460,9 +504,28 @@ static unsigned long swapin_nr_pages(unsigned long offset)
 		pages = max_pages;
 
 	/* Don't shrink readahead too fast */
-	last_ra = atomic_read(&last_readahead_pages) / 2;
+	last_ra = prev_win / 2;
 	if (pages < last_ra)
 		pages = last_ra;
+
+	return pages;
+}
+
+static unsigned long swapin_nr_pages(unsigned long offset)
+{
+	static unsigned long prev_offset;
+	unsigned int hits, pages, max_pages;
+	static atomic_t last_readahead_pages;
+
+	max_pages = 1 << READ_ONCE(page_cluster);
+	if (max_pages <= 1)
+		return 1;
+
+	hits = atomic_xchg(&swapin_readahead_hits, 0);
+	pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages,
+				  atomic_read(&last_readahead_pages));
+	if (!hits)
+		prev_offset = offset;
 	atomic_set(&last_readahead_pages, pages);
 
 	return pages;
@@ -496,7 +559,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	unsigned long start_offset, end_offset;
 	unsigned long mask;
 	struct blk_plug plug;
-	bool do_poll = true;
+	bool do_poll = true, page_allocated;
 
 	mask = swapin_nr_pages(offset) - 1;
 	if (!mask)
@@ -512,12 +575,19 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	blk_start_plug(&plug);
 	for (offset = start_offset; offset <= end_offset ; offset++) {
 		/* Ok, do the async read-ahead now */
-		page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
-						gfp_mask, vma, addr, false);
+		page = __read_swap_cache_async(
+			swp_entry(swp_type(entry), offset),
+			gfp_mask, vma, addr, &page_allocated);
 		if (!page)
 			continue;
-		if (offset != entry_offset && likely(!PageTransCompound(page)))
-			SetPageReadahead(page);
+		if (page_allocated) {
+			swap_readpage(page, false);
+			if (offset != entry_offset &&
+			    likely(!PageTransCompound(page))) {
+				SetPageReadahead(page);
+				count_vm_event(SWAP_RA);
+			}
+		}
 		put_page(page);
 	}
 	blk_finish_plug(&plug);
@@ -561,3 +631,187 @@ void exit_swap_address_space(unsigned int type)
 	synchronize_rcu();
 	kvfree(spaces);
 }
+
+static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
+				     unsigned long faddr,
+				     unsigned long lpfn,
+				     unsigned long rpfn,
+				     unsigned long *start,
+				     unsigned long *end)
+{
+	*start = max3(lpfn, PFN_DOWN(vma->vm_start),
+		      PFN_DOWN(faddr & PMD_MASK));
+	*end = min3(rpfn, PFN_DOWN(vma->vm_end),
+		    PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
+}
+
+struct page *swap_readahead_detect(struct vm_fault *vmf,
+				   struct vma_swap_readahead *swap_ra)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	unsigned long swap_ra_info;
+	struct page *page;
+	swp_entry_t entry;
+	unsigned long faddr, pfn, fpfn;
+	unsigned long start, end;
+	pte_t *pte;
+	unsigned int max_win, hits, prev_win, win, left;
+#ifndef CONFIG_64BIT
+	pte_t *tpte;
+#endif
+
+	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
+			     SWAP_RA_ORDER_CEILING);
+	if (max_win == 1) {
+		swap_ra->win = 1;
+		return NULL;
+	}
+
+	faddr = vmf->address;
+	entry = pte_to_swp_entry(vmf->orig_pte);
+	if ((unlikely(non_swap_entry(entry))))
+		return NULL;
+	page = lookup_swap_cache(entry, vma, faddr);
+	if (page)
+		return page;
+
+	fpfn = PFN_DOWN(faddr);
+	swap_ra_info = GET_SWAP_RA_VAL(vma);
+	pfn = PFN_DOWN(SWAP_RA_ADDR(swap_ra_info));
+	prev_win = SWAP_RA_WIN(swap_ra_info);
+	hits = SWAP_RA_HITS(swap_ra_info);
+	swap_ra->win = win = __swapin_nr_pages(pfn, fpfn, hits,
+					       max_win, prev_win);
+	atomic_long_set(&vma->swap_readahead_info,
+			SWAP_RA_VAL(faddr, win, 0));
+
+	if (win == 1)
+		return NULL;
+
+	/* Copy the PTEs because the page table may be unmapped */
+	if (fpfn == pfn + 1)
+		swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
+	else if (pfn == fpfn + 1)
+		swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
+				  &start, &end);
+	else {
+		left = (win - 1) / 2;
+		swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
+				  &start, &end);
+	}
+	swap_ra->nr_pte = end - start;
+	swap_ra->offset = fpfn - start;
+	pte = vmf->pte - swap_ra->offset;
+#ifdef CONFIG_64BIT
+	swap_ra->ptes = pte;
+#else
+	tpte = swap_ra->ptes;
+	for (pfn = start; pfn != end; pfn++)
+		*tpte++ = *pte++;
+#endif
+
+	return NULL;
+}
+
+struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
+				    struct vm_fault *vmf,
+				    struct vma_swap_readahead *swap_ra)
+{
+	struct blk_plug plug;
+	struct vm_area_struct *vma = vmf->vma;
+	struct page *page;
+	pte_t *pte, pentry;
+	swp_entry_t entry;
+	unsigned int i;
+	bool page_allocated;
+
+	if (swap_ra->win == 1)
+		goto skip;
+
+	blk_start_plug(&plug);
+	for (i = 0, pte = swap_ra->ptes; i < swap_ra->nr_pte;
+	     i++, pte++) {
+		pentry = *pte;
+		if (pte_none(pentry))
+			continue;
+		if (pte_present(pentry))
+			continue;
+		entry = pte_to_swp_entry(pentry);
+		if (unlikely(non_swap_entry(entry)))
+			continue;
+		page = __read_swap_cache_async(entry, gfp_mask, vma,
+					       vmf->address, &page_allocated);
+		if (!page)
+			continue;
+		if (page_allocated) {
+			swap_readpage(page, false);
+			if (i != swap_ra->offset &&
+			    likely(!PageTransCompound(page))) {
+				SetPageReadahead(page);
+				count_vm_event(SWAP_RA);
+			}
+		}
+		put_page(page);
+	}
+	blk_finish_plug(&plug);
+	lru_add_drain();
+skip:
+	return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
+				     swap_ra->win == 1);
+}
+
+#ifdef CONFIG_SYSFS
+static ssize_t vma_ra_enabled_show(struct kobject *kobj,
+				     struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", swap_vma_readahead ? "true" : "false");
+}
+static ssize_t vma_ra_enabled_store(struct kobject *kobj,
+				      struct kobj_attribute *attr,
+				      const char *buf, size_t count)
+{
+	if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
+		swap_vma_readahead = true;
+	else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
+		swap_vma_readahead = false;
+	else
+		return -EINVAL;
+
+	return count;
+}
+static struct kobj_attribute vma_ra_enabled_attr =
+	__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
+	       vma_ra_enabled_store);
+
+static struct attribute *swap_attrs[] = {
+	&vma_ra_enabled_attr.attr,
+	NULL,
+};
+
+static struct attribute_group swap_attr_group = {
+	.attrs = swap_attrs,
+};
+
+static int __init swap_init_sysfs(void)
+{
+	int err;
+	struct kobject *swap_kobj;
+
+	swap_kobj = kobject_create_and_add("swap", mm_kobj);
+	if (!swap_kobj) {
+		pr_err("failed to create swap kobject\n");
+		return -ENOMEM;
+	}
+	err = sysfs_create_group(swap_kobj, &swap_attr_group);
+	if (err) {
+		pr_err("failed to register swap group\n");
+		goto delete_obj;
+	}
+	return 0;
+
+delete_obj:
+	kobject_put(swap_kobj);
+	return err;
+}
+subsys_initcall(swap_init_sysfs);
+#endif