v4.19.13 snapshot.
diff --git a/mm/swap_state.c b/mm/swap_state.c
new file mode 100644
index 0000000..ecee9c6
--- /dev/null
+++ b/mm/swap_state.c
@@ -0,0 +1,853 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/mm/swap_state.c
+ *
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ * Swap reorganised 29.12.95, Stephen Tweedie
+ *
+ * Rewritten to use page cache, (C) 1998 Stephen Tweedie
+ */
+#include <linux/mm.h>
+#include <linux/gfp.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/backing-dev.h>
+#include <linux/blkdev.h>
+#include <linux/pagevec.h>
+#include <linux/migrate.h>
+#include <linux/vmalloc.h>
+#include <linux/swap_slots.h>
+#include <linux/huge_mm.h>
+
+#include <asm/pgtable.h>
+
+/*
+ * swapper_space is a fiction, retained to simplify the path through
+ * vmscan's shrink_page_list.
+ */
+static const struct address_space_operations swap_aops = {
+ .writepage = swap_writepage,
+ .set_page_dirty = swap_set_page_dirty,
+#ifdef CONFIG_MIGRATION
+ .migratepage = migrate_page,
+#endif
+};
+
+struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
+static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
+static bool enable_vma_readahead __read_mostly = 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)
+
+static struct {
+ unsigned long add_total;
+ unsigned long del_total;
+ unsigned long find_success;
+ unsigned long find_total;
+} swap_cache_info;
+
+unsigned long total_swapcache_pages(void)
+{
+ unsigned int i, j, nr;
+ unsigned long ret = 0;
+ struct address_space *spaces;
+
+ rcu_read_lock();
+ for (i = 0; i < MAX_SWAPFILES; i++) {
+ /*
+ * The corresponding entries in nr_swapper_spaces and
+ * swapper_spaces will be reused only after at least
+ * one grace period. So it is impossible for them
+ * belongs to different usage.
+ */
+ nr = nr_swapper_spaces[i];
+ spaces = rcu_dereference(swapper_spaces[i]);
+ if (!nr || !spaces)
+ continue;
+ for (j = 0; j < nr; j++)
+ ret += spaces[j].nrpages;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
+
+void show_swap_cache_info(void)
+{
+ printk("%lu pages in swap cache\n", total_swapcache_pages());
+ printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
+ swap_cache_info.add_total, swap_cache_info.del_total,
+ swap_cache_info.find_success, swap_cache_info.find_total);
+ printk("Free swap = %ldkB\n",
+ get_nr_swap_pages() << (PAGE_SHIFT - 10));
+ printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
+}
+
+/*
+ * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
+ * but sets SwapCache flag and private instead of mapping and index.
+ */
+int __add_to_swap_cache(struct page *page, swp_entry_t entry)
+{
+ int error, i, nr = hpage_nr_pages(page);
+ struct address_space *address_space;
+ pgoff_t idx = swp_offset(entry);
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(PageSwapCache(page), page);
+ VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+
+ page_ref_add(page, nr);
+ SetPageSwapCache(page);
+
+ address_space = swap_address_space(entry);
+ xa_lock_irq(&address_space->i_pages);
+ for (i = 0; i < nr; i++) {
+ set_page_private(page + i, entry.val + i);
+ error = radix_tree_insert(&address_space->i_pages,
+ idx + i, page + i);
+ if (unlikely(error))
+ break;
+ }
+ if (likely(!error)) {
+ address_space->nrpages += nr;
+ __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
+ ADD_CACHE_INFO(add_total, nr);
+ } else {
+ /*
+ * Only the context which have set SWAP_HAS_CACHE flag
+ * would call add_to_swap_cache().
+ * So add_to_swap_cache() doesn't returns -EEXIST.
+ */
+ VM_BUG_ON(error == -EEXIST);
+ set_page_private(page + i, 0UL);
+ while (i--) {
+ radix_tree_delete(&address_space->i_pages, idx + i);
+ set_page_private(page + i, 0UL);
+ }
+ ClearPageSwapCache(page);
+ page_ref_sub(page, nr);
+ }
+ xa_unlock_irq(&address_space->i_pages);
+
+ return error;
+}
+
+
+int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
+{
+ int error;
+
+ error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
+ if (!error) {
+ error = __add_to_swap_cache(page, entry);
+ radix_tree_preload_end();
+ }
+ return error;
+}
+
+/*
+ * This must be called only on pages that have
+ * been verified to be in the swap cache.
+ */
+void __delete_from_swap_cache(struct page *page)
+{
+ struct address_space *address_space;
+ int i, nr = hpage_nr_pages(page);
+ swp_entry_t entry;
+ pgoff_t idx;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageSwapCache(page), page);
+ VM_BUG_ON_PAGE(PageWriteback(page), page);
+
+ entry.val = page_private(page);
+ address_space = swap_address_space(entry);
+ idx = swp_offset(entry);
+ for (i = 0; i < nr; i++) {
+ radix_tree_delete(&address_space->i_pages, idx + i);
+ set_page_private(page + i, 0);
+ }
+ ClearPageSwapCache(page);
+ address_space->nrpages -= nr;
+ __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+ ADD_CACHE_INFO(del_total, nr);
+}
+
+/**
+ * add_to_swap - allocate swap space for a page
+ * @page: page we want to move to swap
+ *
+ * Allocate swap space for the page and add the page to the
+ * swap cache. Caller needs to hold the page lock.
+ */
+int add_to_swap(struct page *page)
+{
+ swp_entry_t entry;
+ int err;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageUptodate(page), page);
+
+ entry = get_swap_page(page);
+ if (!entry.val)
+ return 0;
+
+ /*
+ * Radix-tree node allocations from PF_MEMALLOC contexts could
+ * completely exhaust the page allocator. __GFP_NOMEMALLOC
+ * stops emergency reserves from being allocated.
+ *
+ * TODO: this could cause a theoretical memory reclaim
+ * deadlock in the swap out path.
+ */
+ /*
+ * Add it to the swap cache.
+ */
+ err = add_to_swap_cache(page, entry,
+ __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
+ /* -ENOMEM radix-tree allocation failure */
+ if (err)
+ /*
+ * add_to_swap_cache() doesn't return -EEXIST, so we can safely
+ * 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;
+
+fail:
+ put_swap_page(page, entry);
+ return 0;
+}
+
+/*
+ * This must be called only on pages that have
+ * been verified to be in the swap cache and locked.
+ * It will never put the page into the free list,
+ * the caller has a reference on the page.
+ */
+void delete_from_swap_cache(struct page *page)
+{
+ swp_entry_t entry;
+ struct address_space *address_space;
+
+ entry.val = page_private(page);
+
+ address_space = swap_address_space(entry);
+ xa_lock_irq(&address_space->i_pages);
+ __delete_from_swap_cache(page);
+ xa_unlock_irq(&address_space->i_pages);
+
+ put_swap_page(page, entry);
+ page_ref_sub(page, hpage_nr_pages(page));
+}
+
+/*
+ * If we are the only user, then try to free up the swap cache.
+ *
+ * Its ok to check for PageSwapCache without the page lock
+ * here because we are going to recheck again inside
+ * try_to_free_swap() _with_ the lock.
+ * - Marcelo
+ */
+static inline void free_swap_cache(struct page *page)
+{
+ if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
+ try_to_free_swap(page);
+ unlock_page(page);
+ }
+}
+
+/*
+ * Perform a free_page(), also freeing any swap cache associated with
+ * this page if it is the last user of the page.
+ */
+void free_page_and_swap_cache(struct page *page)
+{
+ free_swap_cache(page);
+ if (!is_huge_zero_page(page))
+ put_page(page);
+}
+
+/*
+ * Passed an array of pages, drop them all from swapcache and then release
+ * them. They are removed from the LRU and freed if this is their last use.
+ */
+void free_pages_and_swap_cache(struct page **pages, int nr)
+{
+ struct page **pagep = pages;
+ int i;
+
+ lru_add_drain();
+ for (i = 0; i < nr; i++)
+ free_swap_cache(pagep[i]);
+ release_pages(pagep, nr);
+}
+
+static inline bool swap_use_vma_readahead(void)
+{
+ return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
+}
+
+/*
+ * Lookup a swap entry in the swap cache. A found page will be returned
+ * unlocked and with its refcount incremented - we rely on the kernel
+ * 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 vm_area_struct *vma,
+ unsigned long addr)
+{
+ struct page *page;
+
+ page = find_get_page(swap_address_space(entry), swp_offset(entry));
+
+ INC_CACHE_INFO(find_total);
+ if (page) {
+ bool vma_ra = swap_use_vma_readahead();
+ bool readahead;
+
+ INC_CACHE_INFO(find_success);
+ /*
+ * At the moment, we don't support PG_readahead for anon THP
+ * so let's bail out rather than confusing the readahead stat.
+ */
+ if (unlikely(PageTransCompound(page)))
+ return page;
+
+ readahead = TestClearPageReadahead(page);
+ if (vma && vma_ra) {
+ unsigned long ra_val;
+ int win, hits;
+
+ ra_val = GET_SWAP_RA_VAL(vma);
+ win = SWAP_RA_WIN(ra_val);
+ hits = SWAP_RA_HITS(ra_val);
+ 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 || !vma_ra)
+ atomic_inc(&swapin_readahead_hits);
+ }
+ }
+
+ return page;
+}
+
+struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr,
+ bool *new_page_allocated)
+{
+ struct page *found_page, *new_page = NULL;
+ struct address_space *swapper_space = swap_address_space(entry);
+ int err;
+ *new_page_allocated = false;
+
+ do {
+ /*
+ * First check the swap cache. Since this is normally
+ * called after lookup_swap_cache() failed, re-calling
+ * that would confuse statistics.
+ */
+ found_page = find_get_page(swapper_space, swp_offset(entry));
+ if (found_page)
+ break;
+
+ /*
+ * Just skip read ahead for unused swap slot.
+ * During swap_off when swap_slot_cache is disabled,
+ * we have to handle the race between putting
+ * swap entry in swap cache and marking swap slot
+ * as SWAP_HAS_CACHE. That's done in later part of code or
+ * else swap_off will be aborted if we return NULL.
+ */
+ if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
+ break;
+
+ /*
+ * Get a new page to read into from swap.
+ */
+ if (!new_page) {
+ new_page = alloc_page_vma(gfp_mask, vma, addr);
+ if (!new_page)
+ break; /* Out of memory */
+ }
+
+ /*
+ * call radix_tree_preload() while we can wait.
+ */
+ err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
+ if (err)
+ break;
+
+ /*
+ * Swap entry may have been freed since our caller observed it.
+ */
+ err = swapcache_prepare(entry);
+ if (err == -EEXIST) {
+ radix_tree_preload_end();
+ /*
+ * We might race against get_swap_page() and stumble
+ * across a SWAP_HAS_CACHE swap_map entry whose page
+ * has not been brought into the swapcache yet.
+ */
+ cond_resched();
+ continue;
+ }
+ if (err) { /* swp entry is obsolete ? */
+ radix_tree_preload_end();
+ break;
+ }
+
+ /* May fail (-ENOMEM) if radix-tree node allocation failed. */
+ __SetPageLocked(new_page);
+ __SetPageSwapBacked(new_page);
+ err = __add_to_swap_cache(new_page, entry);
+ if (likely(!err)) {
+ radix_tree_preload_end();
+ /*
+ * Initiate read into locked page and return.
+ */
+ lru_cache_add_anon(new_page);
+ *new_page_allocated = true;
+ return new_page;
+ }
+ radix_tree_preload_end();
+ __ClearPageLocked(new_page);
+ /*
+ * add_to_swap_cache() doesn't return -EEXIST, so we can safely
+ * clear SWAP_HAS_CACHE flag.
+ */
+ put_swap_page(new_page, entry);
+ } while (err != -ENOMEM);
+
+ if (new_page)
+ put_page(new_page);
+ return found_page;
+}
+
+/*
+ * Locate a page of swap in physical memory, reserving swap cache space
+ * and reading the disk if it is not already cached.
+ * A failure return means that either the page allocation failed or that
+ * the swap entry is no longer in use.
+ */
+struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_area_struct *vma, unsigned long addr, bool do_poll)
+{
+ bool page_was_allocated;
+ struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
+ vma, addr, &page_was_allocated);
+
+ if (page_was_allocated)
+ swap_readpage(retpage, do_poll);
+
+ return retpage;
+}
+
+static unsigned int __swapin_nr_pages(unsigned long prev_offset,
+ unsigned long offset,
+ int hits,
+ int max_pages,
+ int prev_win)
+{
+ 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 = hits + 2;
+ if (pages == 2) {
+ /*
+ * We can have no readahead hits to judge by: but must not get
+ * stuck here forever, so check for an adjacent offset instead
+ * (and don't even bother to check whether swap type is same).
+ */
+ if (offset != prev_offset + 1 && offset != prev_offset - 1)
+ pages = 1;
+ } else {
+ unsigned int roundup = 4;
+ while (roundup < pages)
+ roundup <<= 1;
+ pages = roundup;
+ }
+
+ if (pages > max_pages)
+ pages = max_pages;
+
+ /* Don't shrink readahead too fast */
+ 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;
+}
+
+/**
+ * swap_cluster_readahead - swap in pages in hope we need them soon
+ * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
+ * @vmf: fault information
+ *
+ * Returns the struct page for entry and addr, after queueing swapin.
+ *
+ * Primitive swap readahead code. We simply read an aligned block of
+ * (1 << page_cluster) entries in the swap area. This method is chosen
+ * because it doesn't cost us any seek time. We also make sure to queue
+ * the 'original' request together with the readahead ones...
+ *
+ * This has been extended to use the NUMA policies from the mm triggering
+ * the readahead.
+ *
+ * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.
+ */
+struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_fault *vmf)
+{
+ struct page *page;
+ unsigned long entry_offset = swp_offset(entry);
+ unsigned long offset = entry_offset;
+ unsigned long start_offset, end_offset;
+ unsigned long mask;
+ struct swap_info_struct *si = swp_swap_info(entry);
+ struct blk_plug plug;
+ bool do_poll = true, page_allocated;
+ struct vm_area_struct *vma = vmf->vma;
+ unsigned long addr = vmf->address;
+
+ mask = swapin_nr_pages(offset) - 1;
+ if (!mask)
+ goto skip;
+
+ do_poll = false;
+ /* Read a page_cluster sized and aligned cluster around offset. */
+ start_offset = offset & ~mask;
+ end_offset = offset | mask;
+ if (!start_offset) /* First page is swap header. */
+ start_offset++;
+ if (end_offset >= si->max)
+ end_offset = si->max - 1;
+
+ 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, &page_allocated);
+ if (!page)
+ continue;
+ if (page_allocated) {
+ swap_readpage(page, false);
+ if (offset != entry_offset) {
+ SetPageReadahead(page);
+ count_vm_event(SWAP_RA);
+ }
+ }
+ put_page(page);
+ }
+ blk_finish_plug(&plug);
+
+ lru_add_drain(); /* Push any new pages onto the LRU now */
+skip:
+ return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
+}
+
+int init_swap_address_space(unsigned int type, unsigned long nr_pages)
+{
+ struct address_space *spaces, *space;
+ unsigned int i, nr;
+
+ nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
+ spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
+ if (!spaces)
+ return -ENOMEM;
+ for (i = 0; i < nr; i++) {
+ space = spaces + i;
+ INIT_RADIX_TREE(&space->i_pages, GFP_ATOMIC|__GFP_NOWARN);
+ atomic_set(&space->i_mmap_writable, 0);
+ space->a_ops = &swap_aops;
+ /* swap cache doesn't use writeback related tags */
+ mapping_set_no_writeback_tags(space);
+ }
+ nr_swapper_spaces[type] = nr;
+ rcu_assign_pointer(swapper_spaces[type], spaces);
+
+ return 0;
+}
+
+void exit_swap_address_space(unsigned int type)
+{
+ struct address_space *spaces;
+
+ spaces = swapper_spaces[type];
+ nr_swapper_spaces[type] = 0;
+ rcu_assign_pointer(swapper_spaces[type], NULL);
+ 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));
+}
+
+static void swap_ra_info(struct vm_fault *vmf,
+ struct vma_swap_readahead *ra_info)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ unsigned long ra_val;
+ swp_entry_t entry;
+ unsigned long faddr, pfn, fpfn;
+ unsigned long start, end;
+ pte_t *pte, *orig_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) {
+ ra_info->win = 1;
+ return;
+ }
+
+ faddr = vmf->address;
+ orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
+ entry = pte_to_swp_entry(*pte);
+ if ((unlikely(non_swap_entry(entry)))) {
+ pte_unmap(orig_pte);
+ return;
+ }
+
+ fpfn = PFN_DOWN(faddr);
+ ra_val = GET_SWAP_RA_VAL(vma);
+ pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
+ prev_win = SWAP_RA_WIN(ra_val);
+ hits = SWAP_RA_HITS(ra_val);
+ ra_info->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) {
+ pte_unmap(orig_pte);
+ return;
+ }
+
+ /* 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);
+ }
+ ra_info->nr_pte = end - start;
+ ra_info->offset = fpfn - start;
+ pte -= ra_info->offset;
+#ifdef CONFIG_64BIT
+ ra_info->ptes = pte;
+#else
+ tpte = ra_info->ptes;
+ for (pfn = start; pfn != end; pfn++)
+ *tpte++ = *pte++;
+#endif
+ pte_unmap(orig_pte);
+}
+
+static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
+ struct vm_fault *vmf)
+{
+ 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;
+ struct vma_swap_readahead ra_info = {0,};
+
+ swap_ra_info(vmf, &ra_info);
+ if (ra_info.win == 1)
+ goto skip;
+
+ blk_start_plug(&plug);
+ for (i = 0, pte = ra_info.ptes; i < ra_info.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 != ra_info.offset) {
+ 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,
+ ra_info.win == 1);
+}
+
+/**
+ * swapin_readahead - swap in pages in hope we need them soon
+ * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
+ * @vmf: fault information
+ *
+ * Returns the struct page for entry and addr, after queueing swapin.
+ *
+ * It's a main entry function for swap readahead. By the configuration,
+ * it will read ahead blocks by cluster-based(ie, physical disk based)
+ * or vma-based(ie, virtual address based on faulty address) readahead.
+ */
+struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
+ struct vm_fault *vmf)
+{
+ return swap_use_vma_readahead() ?
+ swap_vma_readahead(entry, gfp_mask, vmf) :
+ swap_cluster_readahead(entry, gfp_mask, vmf);
+}
+
+#ifdef CONFIG_SYSFS
+static ssize_t vma_ra_enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%s\n", enable_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))
+ enable_vma_readahead = true;
+ else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
+ enable_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