Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1672 insertions, 0 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
new file mode 100644
index 000000000000..a60e0075d55b
--- /dev/null
+++ b/mm/swapfile.c
@@ -0,0 +1,1672 @@
+/*
+ *  linux/mm/swapfile.c
+ *
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *  Swap reorganised 29.12.95, Stephen Tweedie
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/mman.h>
+#include <linux/slab.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/vmalloc.h>
+#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/shm.h>
+#include <linux/blkdev.h>
+#include <linux/writeback.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/rmap.h>
+#include <linux/security.h>
+#include <linux/backing-dev.h>
+#include <linux/syscalls.h>
+
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+#include <linux/swapops.h>
+
+DEFINE_SPINLOCK(swaplock);
+unsigned int nr_swapfiles;
+long total_swap_pages;
+static int swap_overflow;
+
+EXPORT_SYMBOL(total_swap_pages);
+
+static const char Bad_file[] = "Bad swap file entry ";
+static const char Unused_file[] = "Unused swap file entry ";
+static const char Bad_offset[] = "Bad swap offset entry ";
+static const char Unused_offset[] = "Unused swap offset entry ";
+
+struct swap_list_t swap_list = {-1, -1};
+
+struct swap_info_struct swap_info[MAX_SWAPFILES];
+
+static DECLARE_MUTEX(swapon_sem);
+
+/*
+ * We need this because the bdev->unplug_fn can sleep and we cannot
+ * hold swap_list_lock while calling the unplug_fn. And swap_list_lock
+ * cannot be turned into a semaphore.
+ */
+static DECLARE_RWSEM(swap_unplug_sem);
+
+#define SWAPFILE_CLUSTER 256
+
+void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
+{
+	swp_entry_t entry;
+
+	down_read(&swap_unplug_sem);
+	entry.val = page->private;
+	if (PageSwapCache(page)) {
+		struct block_device *bdev = swap_info[swp_type(entry)].bdev;
+		struct backing_dev_info *bdi;
+
+		/*
+		 * If the page is removed from swapcache from under us (with a
+		 * racy try_to_unuse/swapoff) we need an additional reference
+		 * count to avoid reading garbage from page->private above. If
+		 * the WARN_ON triggers during a swapoff it maybe the race
+		 * condition and it's harmless. However if it triggers without
+		 * swapoff it signals a problem.
+		 */
+		WARN_ON(page_count(page) <= 1);
+
+		bdi = bdev->bd_inode->i_mapping->backing_dev_info;
+		bdi->unplug_io_fn(bdi, page);
+	}
+	up_read(&swap_unplug_sem);
+}
+
+static inline int scan_swap_map(struct swap_info_struct *si)
+{
+	unsigned long offset;
+	/* 
+	 * We try to cluster swap pages by allocating them
+	 * sequentially in swap.  Once we've allocated
+	 * SWAPFILE_CLUSTER pages this way, however, we resort to
+	 * first-free allocation, starting a new cluster.  This
+	 * prevents us from scattering swap pages all over the entire
+	 * swap partition, so that we reduce overall disk seek times
+	 * between swap pages.  -- sct */
+	if (si->cluster_nr) {
+		while (si->cluster_next <= si->highest_bit) {
+			offset = si->cluster_next++;
+			if (si->swap_map[offset])
+				continue;
+			si->cluster_nr--;
+			goto got_page;
+		}
+	}
+	si->cluster_nr = SWAPFILE_CLUSTER;
+
+	/* try to find an empty (even not aligned) cluster. */
+	offset = si->lowest_bit;
+ check_next_cluster:
+	if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
+	{
+		unsigned long nr;
+		for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
+			if (si->swap_map[nr])
+			{
+				offset = nr+1;
+				goto check_next_cluster;
+			}
+		/* We found a completly empty cluster, so start
+		 * using it.
+		 */
+		goto got_page;
+	}
+	/* No luck, so now go finegrined as usual. -Andrea */
+	for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
+		if (si->swap_map[offset])
+			continue;
+		si->lowest_bit = offset+1;
+	got_page:
+		if (offset == si->lowest_bit)
+			si->lowest_bit++;
+		if (offset == si->highest_bit)
+			si->highest_bit--;
+		if (si->lowest_bit > si->highest_bit) {
+			si->lowest_bit = si->max;
+			si->highest_bit = 0;
+		}
+		si->swap_map[offset] = 1;
+		si->inuse_pages++;
+		nr_swap_pages--;
+		si->cluster_next = offset+1;
+		return offset;
+	}
+	si->lowest_bit = si->max;
+	si->highest_bit = 0;
+	return 0;
+}
+
+swp_entry_t get_swap_page(void)
+{
+	struct swap_info_struct * p;
+	unsigned long offset;
+	swp_entry_t entry;
+	int type, wrapped = 0;
+
+	entry.val = 0;	/* Out of memory */
+	swap_list_lock();
+	type = swap_list.next;
+	if (type < 0)
+		goto out;
+	if (nr_swap_pages <= 0)
+		goto out;
+
+	while (1) {
+		p = &swap_info[type];
+		if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
+			swap_device_lock(p);
+			offset = scan_swap_map(p);
+			swap_device_unlock(p);
+			if (offset) {
+				entry = swp_entry(type,offset);
+				type = swap_info[type].next;
+				if (type < 0 ||
+					p->prio != swap_info[type].prio) {
+						swap_list.next = swap_list.head;
+				} else {
+					swap_list.next = type;
+				}
+				goto out;
+			}
+		}
+		type = p->next;
+		if (!wrapped) {
+			if (type < 0 || p->prio != swap_info[type].prio) {
+				type = swap_list.head;
+				wrapped = 1;
+			}
+		} else
+			if (type < 0)
+				goto out;	/* out of swap space */
+	}
+out:
+	swap_list_unlock();
+	return entry;
+}
+
+static struct swap_info_struct * swap_info_get(swp_entry_t entry)
+{
+	struct swap_info_struct * p;
+	unsigned long offset, type;
+
+	if (!entry.val)
+		goto out;
+	type = swp_type(entry);
+	if (type >= nr_swapfiles)
+		goto bad_nofile;
+	p = & swap_info[type];
+	if (!(p->flags & SWP_USED))
+		goto bad_device;
+	offset = swp_offset(entry);
+	if (offset >= p->max)
+		goto bad_offset;
+	if (!p->swap_map[offset])
+		goto bad_free;
+	swap_list_lock();
+	if (p->prio > swap_info[swap_list.next].prio)
+		swap_list.next = type;
+	swap_device_lock(p);
+	return p;
+
+bad_free:
+	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
+	goto out;
+bad_offset:
+	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
+	goto out;
+bad_device:
+	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
+	goto out;
+bad_nofile:
+	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
+out:
+	return NULL;
+}	
+
+static void swap_info_put(struct swap_info_struct * p)
+{
+	swap_device_unlock(p);
+	swap_list_unlock();
+}
+
+static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
+{
+	int count = p->swap_map[offset];
+
+	if (count < SWAP_MAP_MAX) {
+		count--;
+		p->swap_map[offset] = count;
+		if (!count) {
+			if (offset < p->lowest_bit)
+				p->lowest_bit = offset;
+			if (offset > p->highest_bit)
+				p->highest_bit = offset;
+			nr_swap_pages++;
+			p->inuse_pages--;
+		}
+	}
+	return count;
+}
+
+/*
+ * Caller has made sure that the swapdevice corresponding to entry
+ * is still around or has not been recycled.
+ */
+void swap_free(swp_entry_t entry)
+{
+	struct swap_info_struct * p;
+
+	p = swap_info_get(entry);
+	if (p) {
+		swap_entry_free(p, swp_offset(entry));
+		swap_info_put(p);
+	}
+}
+
+/*
+ * Check if we're the only user of a swap page,
+ * when the page is locked.
+ */
+static int exclusive_swap_page(struct page *page)
+{
+	int retval = 0;
+	struct swap_info_struct * p;
+	swp_entry_t entry;
+
+	entry.val = page->private;
+	p = swap_info_get(entry);
+	if (p) {
+		/* Is the only swap cache user the cache itself? */
+		if (p->swap_map[swp_offset(entry)] == 1) {
+			/* Recheck the page count with the swapcache lock held.. */
+			write_lock_irq(&swapper_space.tree_lock);
+			if (page_count(page) == 2)
+				retval = 1;
+			write_unlock_irq(&swapper_space.tree_lock);
+		}
+		swap_info_put(p);
+	}
+	return retval;
+}
+
+/*
+ * We can use this swap cache entry directly
+ * if there are no other references to it.
+ *
+ * Here "exclusive_swap_page()" does the real
+ * work, but we opportunistically check whether
+ * we need to get all the locks first..
+ */
+int can_share_swap_page(struct page *page)
+{
+	int retval = 0;
+
+	if (!PageLocked(page))
+		BUG();
+	switch (page_count(page)) {
+	case 3:
+		if (!PagePrivate(page))
+			break;
+		/* Fallthrough */
+	case 2:
+		if (!PageSwapCache(page))
+			break;
+		retval = exclusive_swap_page(page);
+		break;
+	case 1:
+		if (PageReserved(page))
+			break;
+		retval = 1;
+	}
+	return retval;
+}
+
+/*
+ * Work out if there are any other processes sharing this
+ * swap cache page. Free it if you can. Return success.
+ */
+int remove_exclusive_swap_page(struct page *page)
+{
+	int retval;
+	struct swap_info_struct * p;
+	swp_entry_t entry;
+
+	BUG_ON(PagePrivate(page));
+	BUG_ON(!PageLocked(page));
+
+	if (!PageSwapCache(page))
+		return 0;
+	if (PageWriteback(page))
+		return 0;
+	if (page_count(page) != 2) /* 2: us + cache */
+		return 0;
+
+	entry.val = page->private;
+	p = swap_info_get(entry);
+	if (!p)
+		return 0;
+
+	/* Is the only swap cache user the cache itself? */
+	retval = 0;
+	if (p->swap_map[swp_offset(entry)] == 1) {
+		/* Recheck the page count with the swapcache lock held.. */
+		write_lock_irq(&swapper_space.tree_lock);
+		if ((page_count(page) == 2) && !PageWriteback(page)) {
+			__delete_from_swap_cache(page);
+			SetPageDirty(page);
+			retval = 1;
+		}
+		write_unlock_irq(&swapper_space.tree_lock);
+	}
+	swap_info_put(p);
+
+	if (retval) {
+		swap_free(entry);
+		page_cache_release(page);
+	}
+
+	return retval;
+}
+
+/*
+ * Free the swap entry like above, but also try to
+ * free the page cache entry if it is the last user.
+ */
+void free_swap_and_cache(swp_entry_t entry)
+{
+	struct swap_info_struct * p;
+	struct page *page = NULL;
+
+	p = swap_info_get(entry);
+	if (p) {
+		if (swap_entry_free(p, swp_offset(entry)) == 1)
+			page = find_trylock_page(&swapper_space, entry.val);
+		swap_info_put(p);
+	}
+	if (page) {
+		int one_user;
+
+		BUG_ON(PagePrivate(page));
+		page_cache_get(page);
+		one_user = (page_count(page) == 2);
+		/* Only cache user (+us), or swap space full? Free it! */
+		if (!PageWriteback(page) && (one_user || vm_swap_full())) {
+			delete_from_swap_cache(page);
+			SetPageDirty(page);
+		}
+		unlock_page(page);
+		page_cache_release(page);
+	}
+}
+
+/*
+ * Always set the resulting pte to be nowrite (the same as COW pages
+ * after one process has exited).  We don't know just how many PTEs will
+ * share this swap entry, so be cautious and let do_wp_page work out
+ * what to do if a write is requested later.
+ *
+ * vma->vm_mm->page_table_lock is held.
+ */
+static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
+		unsigned long addr, swp_entry_t entry, struct page *page)
+{
+	inc_mm_counter(vma->vm_mm, rss);
+	get_page(page);
+	set_pte_at(vma->vm_mm, addr, pte,
+		   pte_mkold(mk_pte(page, vma->vm_page_prot)));
+	page_add_anon_rmap(page, vma, addr);
+	swap_free(entry);
+	/*
+	 * Move the page to the active list so it is not
+	 * immediately swapped out again after swapon.
+	 */
+	activate_page(page);
+}
+
+static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
+				unsigned long addr, unsigned long end,
+				swp_entry_t entry, struct page *page)
+{
+	pte_t *pte;
+	pte_t swp_pte = swp_entry_to_pte(entry);
+
+	pte = pte_offset_map(pmd, addr);
+	do {
+		/*
+		 * swapoff spends a _lot_ of time in this loop!
+		 * Test inline before going to call unuse_pte.
+		 */
+		if (unlikely(pte_same(*pte, swp_pte))) {
+			unuse_pte(vma, pte, addr, entry, page);
+			pte_unmap(pte);
+			return 1;
+		}
+	} while (pte++, addr += PAGE_SIZE, addr != end);
+	pte_unmap(pte - 1);
+	return 0;
+}
+
+static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
+				unsigned long addr, unsigned long end,
+				swp_entry_t entry, struct page *page)
+{
+	pmd_t *pmd;
+	unsigned long next;
+
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none_or_clear_bad(pmd))
+			continue;
+		if (unuse_pte_range(vma, pmd, addr, next, entry, page))
+			return 1;
+	} while (pmd++, addr = next, addr != end);
+	return 0;
+}
+
+static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
+				unsigned long addr, unsigned long end,
+				swp_entry_t entry, struct page *page)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		if (unuse_pmd_range(vma, pud, addr, next, entry, page))
+			return 1;
+	} while (pud++, addr = next, addr != end);
+	return 0;
+}
+
+static int unuse_vma(struct vm_area_struct *vma,
+				swp_entry_t entry, struct page *page)
+{
+	pgd_t *pgd;
+	unsigned long addr, end, next;
+
+	if (page->mapping) {
+		addr = page_address_in_vma(page, vma);
+		if (addr == -EFAULT)
+			return 0;
+		else
+			end = addr + PAGE_SIZE;
+	} else {
+		addr = vma->vm_start;
+		end = vma->vm_end;
+	}
+
+	pgd = pgd_offset(vma->vm_mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		if (unuse_pud_range(vma, pgd, addr, next, entry, page))
+			return 1;
+	} while (pgd++, addr = next, addr != end);
+	return 0;
+}
+
+static int unuse_mm(struct mm_struct *mm,
+				swp_entry_t entry, struct page *page)
+{
+	struct vm_area_struct *vma;
+
+	if (!down_read_trylock(&mm->mmap_sem)) {
+		/*
+		 * Our reference to the page stops try_to_unmap_one from
+		 * unmapping its ptes, so swapoff can make progress.
+		 */
+		unlock_page(page);
+		down_read(&mm->mmap_sem);
+		lock_page(page);
+	}
+	spin_lock(&mm->page_table_lock);
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		if (vma->anon_vma && unuse_vma(vma, entry, page))
+			break;
+	}
+	spin_unlock(&mm->page_table_lock);
+	up_read(&mm->mmap_sem);
+	/*
+	 * Currently unuse_mm cannot fail, but leave error handling
+	 * at call sites for now, since we change it from time to time.
+	 */
+	return 0;
+}
+
+/*
+ * Scan swap_map from current position to next entry still in use.
+ * Recycle to start on reaching the end, returning 0 when empty.
+ */
+static int find_next_to_unuse(struct swap_info_struct *si, int prev)
+{
+	int max = si->max;
+	int i = prev;
+	int count;
+
+	/*
+	 * No need for swap_device_lock(si) here: we're just looking
+	 * for whether an entry is in use, not modifying it; false
+	 * hits are okay, and sys_swapoff() has already prevented new
+	 * allocations from this area (while holding swap_list_lock()).
+	 */
+	for (;;) {
+		if (++i >= max) {
+			if (!prev) {
+				i = 0;
+				break;
+			}
+			/*
+			 * No entries in use at top of swap_map,
+			 * loop back to start and recheck there.
+			 */
+			max = prev + 1;
+			prev = 0;
+			i = 1;
+		}
+		count = si->swap_map[i];
+		if (count && count != SWAP_MAP_BAD)
+			break;
+	}
+	return i;
+}
+
+/*
+ * We completely avoid races by reading each swap page in advance,
+ * and then search for the process using it.  All the necessary
+ * page table adjustments can then be made atomically.
+ */
+static int try_to_unuse(unsigned int type)
+{
+	struct swap_info_struct * si = &swap_info[type];
+	struct mm_struct *start_mm;
+	unsigned short *swap_map;
+	unsigned short swcount;
+	struct page *page;
+	swp_entry_t entry;
+	int i = 0;
+	int retval = 0;
+	int reset_overflow = 0;
+	int shmem;
+
+	/*
+	 * When searching mms for an entry, a good strategy is to
+	 * start at the first mm we freed the previous entry from
+	 * (though actually we don't notice whether we or coincidence
+	 * freed the entry).  Initialize this start_mm with a hold.
+	 *
+	 * A simpler strategy would be to start at the last mm we
+	 * freed the previous entry from; but that would take less
+	 * advantage of mmlist ordering, which clusters forked mms
+	 * together, child after parent.  If we race with dup_mmap(), we
+	 * prefer to resolve parent before child, lest we miss entries
+	 * duplicated after we scanned child: using last mm would invert
+	 * that.  Though it's only a serious concern when an overflowed
+	 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
+	 */
+	start_mm = &init_mm;
+	atomic_inc(&init_mm.mm_users);
+
+	/*
+	 * Keep on scanning until all entries have gone.  Usually,
+	 * one pass through swap_map is enough, but not necessarily:
+	 * there are races when an instance of an entry might be missed.
+	 */
+	while ((i = find_next_to_unuse(si, i)) != 0) {
+		if (signal_pending(current)) {
+			retval = -EINTR;
+			break;
+		}
+
+		/* 
+		 * Get a page for the entry, using the existing swap
+		 * cache page if there is one.  Otherwise, get a clean
+		 * page and read the swap into it. 
+		 */
+		swap_map = &si->swap_map[i];
+		entry = swp_entry(type, i);
+		page = read_swap_cache_async(entry, NULL, 0);
+		if (!page) {
+			/*
+			 * Either swap_duplicate() failed because entry
+			 * has been freed independently, and will not be
+			 * reused since sys_swapoff() already disabled
+			 * allocation from here, or alloc_page() failed.
+			 */
+			if (!*swap_map)
+				continue;
+			retval = -ENOMEM;
+			break;
+		}
+
+		/*
+		 * Don't hold on to start_mm if it looks like exiting.
+		 */
+		if (atomic_read(&start_mm->mm_users) == 1) {
+			mmput(start_mm);
+			start_mm = &init_mm;
+			atomic_inc(&init_mm.mm_users);
+		}
+
+		/*
+		 * Wait for and lock page.  When do_swap_page races with
+		 * try_to_unuse, do_swap_page can handle the fault much
+		 * faster than try_to_unuse can locate the entry.  This
+		 * apparently redundant "wait_on_page_locked" lets try_to_unuse
+		 * defer to do_swap_page in such a case - in some tests,
+		 * do_swap_page and try_to_unuse repeatedly compete.
+		 */
+		wait_on_page_locked(page);
+		wait_on_page_writeback(page);
+		lock_page(page);
+		wait_on_page_writeback(page);
+
+		/*
+		 * Remove all references to entry.
+		 * Whenever we reach init_mm, there's no address space
+		 * to search, but use it as a reminder to search shmem.
+		 */
+		shmem = 0;
+		swcount = *swap_map;
+		if (swcount > 1) {
+			if (start_mm == &init_mm)
+				shmem = shmem_unuse(entry, page);
+			else
+				retval = unuse_mm(start_mm, entry, page);
+		}
+		if (*swap_map > 1) {
+			int set_start_mm = (*swap_map >= swcount);
+			struct list_head *p = &start_mm->mmlist;
+			struct mm_struct *new_start_mm = start_mm;
+			struct mm_struct *prev_mm = start_mm;
+			struct mm_struct *mm;
+
+			atomic_inc(&new_start_mm->mm_users);
+			atomic_inc(&prev_mm->mm_users);
+			spin_lock(&mmlist_lock);
+			while (*swap_map > 1 && !retval &&
+					(p = p->next) != &start_mm->mmlist) {
+				mm = list_entry(p, struct mm_struct, mmlist);
+				if (atomic_inc_return(&mm->mm_users) == 1) {
+					atomic_dec(&mm->mm_users);
+					continue;
+				}
+				spin_unlock(&mmlist_lock);
+				mmput(prev_mm);
+				prev_mm = mm;
+
+				cond_resched();
+
+				swcount = *swap_map;
+				if (swcount <= 1)
+					;
+				else if (mm == &init_mm) {
+					set_start_mm = 1;
+					shmem = shmem_unuse(entry, page);
+				} else
+					retval = unuse_mm(mm, entry, page);
+				if (set_start_mm && *swap_map < swcount) {
+					mmput(new_start_mm);
+					atomic_inc(&mm->mm_users);
+					new_start_mm = mm;
+					set_start_mm = 0;
+				}
+				spin_lock(&mmlist_lock);
+			}
+			spin_unlock(&mmlist_lock);
+			mmput(prev_mm);
+			mmput(start_mm);
+			start_mm = new_start_mm;
+		}
+		if (retval) {
+			unlock_page(page);
+			page_cache_release(page);
+			break;
+		}
+
+		/*
+		 * How could swap count reach 0x7fff when the maximum
+		 * pid is 0x7fff, and there's no way to repeat a swap
+		 * page within an mm (except in shmem, where it's the
+		 * shared object which takes the reference count)?
+		 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
+		 *
+		 * If that's wrong, then we should worry more about
+		 * exit_mmap() and do_munmap() cases described above:
+		 * we might be resetting SWAP_MAP_MAX too early here.
+		 * We know "Undead"s can happen, they're okay, so don't
+		 * report them; but do report if we reset SWAP_MAP_MAX.
+		 */
+		if (*swap_map == SWAP_MAP_MAX) {
+			swap_device_lock(si);
+			*swap_map = 1;
+			swap_device_unlock(si);
+			reset_overflow = 1;
+		}
+
+		/*
+		 * If a reference remains (rare), we would like to leave
+		 * the page in the swap cache; but try_to_unmap could
+		 * then re-duplicate the entry once we drop page lock,
+		 * so we might loop indefinitely; also, that page could
+		 * not be swapped out to other storage meanwhile.  So:
+		 * delete from cache even if there's another reference,
+		 * after ensuring that the data has been saved to disk -
+		 * since if the reference remains (rarer), it will be
+		 * read from disk into another page.  Splitting into two
+		 * pages would be incorrect if swap supported "shared
+		 * private" pages, but they are handled by tmpfs files.
+		 *
+		 * Note shmem_unuse already deleted a swappage from
+		 * the swap cache, unless the move to filepage failed:
+		 * in which case it left swappage in cache, lowered its
+		 * swap count to pass quickly through the loops above,
+		 * and now we must reincrement count to try again later.
+		 */
+		if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
+			struct writeback_control wbc = {
+				.sync_mode = WB_SYNC_NONE,
+			};
+
+			swap_writepage(page, &wbc);
+			lock_page(page);
+			wait_on_page_writeback(page);
+		}
+		if (PageSwapCache(page)) {
+			if (shmem)
+				swap_duplicate(entry);
+			else
+				delete_from_swap_cache(page);
+		}
+
+		/*
+		 * So we could skip searching mms once swap count went
+		 * to 1, we did not mark any present ptes as dirty: must
+		 * mark page dirty so shrink_list will preserve it.
+		 */
+		SetPageDirty(page);
+		unlock_page(page);
+		page_cache_release(page);
+
+		/*
+		 * Make sure that we aren't completely killing
+		 * interactive performance.
+		 */
+		cond_resched();
+	}
+
+	mmput(start_mm);
+	if (reset_overflow) {
+		printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
+		swap_overflow = 0;
+	}
+	return retval;
+}
+
+/*
+ * After a successful try_to_unuse, if no swap is now in use, we know we
+ * can empty the mmlist.  swap_list_lock must be held on entry and exit.
+ * Note that mmlist_lock nests inside swap_list_lock, and an mm must be
+ * added to the mmlist just after page_duplicate - before would be racy.
+ */
+static void drain_mmlist(void)
+{
+	struct list_head *p, *next;
+	unsigned int i;
+
+	for (i = 0; i < nr_swapfiles; i++)
+		if (swap_info[i].inuse_pages)
+			return;
+	spin_lock(&mmlist_lock);
+	list_for_each_safe(p, next, &init_mm.mmlist)
+		list_del_init(p);
+	spin_unlock(&mmlist_lock);
+}
+
+/*
+ * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
+ * corresponds to page offset `offset'.
+ */
+sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
+{
+	struct swap_extent *se = sis->curr_swap_extent;
+	struct swap_extent *start_se = se;
+
+	for ( ; ; ) {
+		struct list_head *lh;
+
+		if (se->start_page <= offset &&
+				offset < (se->start_page + se->nr_pages)) {
+			return se->start_block + (offset - se->start_page);
+		}
+		lh = se->list.prev;
+		if (lh == &sis->extent_list)
+			lh = lh->prev;
+		se = list_entry(lh, struct swap_extent, list);
+		sis->curr_swap_extent = se;
+		BUG_ON(se == start_se);		/* It *must* be present */
+	}
+}
+
+/*
+ * Free all of a swapdev's extent information
+ */
+static void destroy_swap_extents(struct swap_info_struct *sis)
+{
+	while (!list_empty(&sis->extent_list)) {
+		struct swap_extent *se;
+
+		se = list_entry(sis->extent_list.next,
+				struct swap_extent, list);
+		list_del(&se->list);
+		kfree(se);
+	}
+	sis->nr_extents = 0;
+}
+
+/*
+ * Add a block range (and the corresponding page range) into this swapdev's
+ * extent list.  The extent list is kept sorted in block order.
+ *
+ * This function rather assumes that it is called in ascending sector_t order.
+ * It doesn't look for extent coalescing opportunities.
+ */
+static int
+add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
+		unsigned long nr_pages, sector_t start_block)
+{
+	struct swap_extent *se;
+	struct swap_extent *new_se;
+	struct list_head *lh;
+
+	lh = sis->extent_list.next;	/* The highest-addressed block */
+	while (lh != &sis->extent_list) {
+		se = list_entry(lh, struct swap_extent, list);
+		if (se->start_block + se->nr_pages == start_block &&
+		    se->start_page  + se->nr_pages == start_page) {
+			/* Merge it */
+			se->nr_pages += nr_pages;
+			return 0;
+		}
+		lh = lh->next;
+	}
+
+	/*
+	 * No merge.  Insert a new extent, preserving ordering.
+	 */
+	new_se = kmalloc(sizeof(*se), GFP_KERNEL);
+	if (new_se == NULL)
+		return -ENOMEM;
+	new_se->start_page = start_page;
+	new_se->nr_pages = nr_pages;
+	new_se->start_block = start_block;
+
+	lh = sis->extent_list.prev;	/* The lowest block */
+	while (lh != &sis->extent_list) {
+		se = list_entry(lh, struct swap_extent, list);
+		if (se->start_block > start_block)
+			break;
+		lh = lh->prev;
+	}
+	list_add_tail(&new_se->list, lh);
+	sis->nr_extents++;
+	return 0;
+}
+
+/*
+ * A `swap extent' is a simple thing which maps a contiguous range of pages
+ * onto a contiguous range of disk blocks.  An ordered list of swap extents
+ * is built at swapon time and is then used at swap_writepage/swap_readpage
+ * time for locating where on disk a page belongs.
+ *
+ * If the swapfile is an S_ISBLK block device, a single extent is installed.
+ * This is done so that the main operating code can treat S_ISBLK and S_ISREG
+ * swap files identically.
+ *
+ * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
+ * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
+ * swapfiles are handled *identically* after swapon time.
+ *
+ * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
+ * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
+ * some stray blocks are found which do not fall within the PAGE_SIZE alignment
+ * requirements, they are simply tossed out - we will never use those blocks
+ * for swapping.
+ *
+ * For S_ISREG swapfiles we hold i_sem across the life of the swapon.  This
+ * prevents root from shooting her foot off by ftruncating an in-use swapfile,
+ * which will scribble on the fs.
+ *
+ * The amount of disk space which a single swap extent represents varies.
+ * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
+ * extents in the list.  To avoid much list walking, we cache the previous
+ * search location in `curr_swap_extent', and start new searches from there.
+ * This is extremely effective.  The average number of iterations in
+ * map_swap_page() has been measured at about 0.3 per page.  - akpm.
+ */
+static int setup_swap_extents(struct swap_info_struct *sis)
+{
+	struct inode *inode;
+	unsigned blocks_per_page;
+	unsigned long page_no;
+	unsigned blkbits;
+	sector_t probe_block;
+	sector_t last_block;
+	int ret;
+
+	inode = sis->swap_file->f_mapping->host;
+	if (S_ISBLK(inode->i_mode)) {
+		ret = add_swap_extent(sis, 0, sis->max, 0);
+		goto done;
+	}
+
+	blkbits = inode->i_blkbits;
+	blocks_per_page = PAGE_SIZE >> blkbits;
+
+	/*
+	 * Map all the blocks into the extent list.  This code doesn't try
+	 * to be very smart.
+	 */
+	probe_block = 0;
+	page_no = 0;
+	last_block = i_size_read(inode) >> blkbits;
+	while ((probe_block + blocks_per_page) <= last_block &&
+			page_no < sis->max) {
+		unsigned block_in_page;
+		sector_t first_block;
+
+		first_block = bmap(inode, probe_block);
+		if (first_block == 0)
+			goto bad_bmap;
+
+		/*
+		 * It must be PAGE_SIZE aligned on-disk
+		 */
+		if (first_block & (blocks_per_page - 1)) {
+			probe_block++;
+			goto reprobe;
+		}
+
+		for (block_in_page = 1; block_in_page < blocks_per_page;
+					block_in_page++) {
+			sector_t block;
+
+			block = bmap(inode, probe_block + block_in_page);
+			if (block == 0)
+				goto bad_bmap;
+			if (block != first_block + block_in_page) {
+				/* Discontiguity */
+				probe_block++;
+				goto reprobe;
+			}
+		}
+
+		/*
+		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
+		 */
+		ret = add_swap_extent(sis, page_no, 1,
+				first_block >> (PAGE_SHIFT - blkbits));
+		if (ret)
+			goto out;
+		page_no++;
+		probe_block += blocks_per_page;
+reprobe:
+		continue;
+	}
+	ret = 0;
+	if (page_no == 0)
+		ret = -EINVAL;
+	sis->max = page_no;
+	sis->highest_bit = page_no - 1;
+done:
+	sis->curr_swap_extent = list_entry(sis->extent_list.prev,
+					struct swap_extent, list);
+	goto out;
+bad_bmap:
+	printk(KERN_ERR "swapon: swapfile has holes\n");
+	ret = -EINVAL;
+out:
+	return ret;
+}
+
+#if 0	/* We don't need this yet */
+#include <linux/backing-dev.h>
+int page_queue_congested(struct page *page)
+{
+	struct backing_dev_info *bdi;
+
+	BUG_ON(!PageLocked(page));	/* It pins the swap_info_struct */
+
+	if (PageSwapCache(page)) {
+		swp_entry_t entry = { .val = page->private };
+		struct swap_info_struct *sis;
+
+		sis = get_swap_info_struct(swp_type(entry));
+		bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
+	} else
+		bdi = page->mapping->backing_dev_info;
+	return bdi_write_congested(bdi);
+}
+#endif
+
+asmlinkage long sys_swapoff(const char __user * specialfile)
+{
+	struct swap_info_struct * p = NULL;
+	unsigned short *swap_map;
+	struct file *swap_file, *victim;
+	struct address_space *mapping;
+	struct inode *inode;
+	char * pathname;
+	int i, type, prev;
+	int err;
+	
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	pathname = getname(specialfile);
+	err = PTR_ERR(pathname);
+	if (IS_ERR(pathname))
+		goto out;
+
+	victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
+	putname(pathname);
+	err = PTR_ERR(victim);
+	if (IS_ERR(victim))
+		goto out;
+
+	mapping = victim->f_mapping;
+	prev = -1;
+	swap_list_lock();
+	for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
+		p = swap_info + type;
+		if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
+			if (p->swap_file->f_mapping == mapping)
+				break;
+		}
+		prev = type;
+	}
+	if (type < 0) {
+		err = -EINVAL;
+		swap_list_unlock();
+		goto out_dput;
+	}
+	if (!security_vm_enough_memory(p->pages))
+		vm_unacct_memory(p->pages);
+	else {
+		err = -ENOMEM;
+		swap_list_unlock();
+		goto out_dput;
+	}
+	if (prev < 0) {
+		swap_list.head = p->next;
+	} else {
+		swap_info[prev].next = p->next;
+	}
+	if (type == swap_list.next) {
+		/* just pick something that's safe... */
+		swap_list.next = swap_list.head;
+	}
+	nr_swap_pages -= p->pages;
+	total_swap_pages -= p->pages;
+	p->flags &= ~SWP_WRITEOK;
+	swap_list_unlock();
+	current->flags |= PF_SWAPOFF;
+	err = try_to_unuse(type);
+	current->flags &= ~PF_SWAPOFF;
+
+	/* wait for any unplug function to finish */
+	down_write(&swap_unplug_sem);
+	up_write(&swap_unplug_sem);
+
+	if (err) {
+		/* re-insert swap space back into swap_list */
+		swap_list_lock();
+		for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
+			if (p->prio >= swap_info[i].prio)
+				break;
+		p->next = i;
+		if (prev < 0)
+			swap_list.head = swap_list.next = p - swap_info;
+		else
+			swap_info[prev].next = p - swap_info;
+		nr_swap_pages += p->pages;
+		total_swap_pages += p->pages;
+		p->flags |= SWP_WRITEOK;
+		swap_list_unlock();
+		goto out_dput;
+	}
+	down(&swapon_sem);
+	swap_list_lock();
+	drain_mmlist();
+	swap_device_lock(p);
+	swap_file = p->swap_file;
+	p->swap_file = NULL;
+	p->max = 0;
+	swap_map = p->swap_map;
+	p->swap_map = NULL;
+	p->flags = 0;
+	destroy_swap_extents(p);
+	swap_device_unlock(p);
+	swap_list_unlock();
+	up(&swapon_sem);
+	vfree(swap_map);
+	inode = mapping->host;
+	if (S_ISBLK(inode->i_mode)) {
+		struct block_device *bdev = I_BDEV(inode);
+		set_blocksize(bdev, p->old_block_size);
+		bd_release(bdev);
+	} else {
+		down(&inode->i_sem);
+		inode->i_flags &= ~S_SWAPFILE;
+		up(&inode->i_sem);
+	}
+	filp_close(swap_file, NULL);
+	err = 0;
+
+out_dput:
+	filp_close(victim, NULL);
+out:
+	return err;
+}
+
+#ifdef CONFIG_PROC_FS
+/* iterator */
+static void *swap_start(struct seq_file *swap, loff_t *pos)
+{
+	struct swap_info_struct *ptr = swap_info;
+	int i;
+	loff_t l = *pos;
+
+	down(&swapon_sem);
+
+	for (i = 0; i < nr_swapfiles; i++, ptr++) {
+		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
+			continue;
+		if (!l--)
+			return ptr;
+	}
+
+	return NULL;
+}
+
+static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
+{
+	struct swap_info_struct *ptr = v;
+	struct swap_info_struct *endptr = swap_info + nr_swapfiles;
+
+	for (++ptr; ptr < endptr; ptr++) {
+		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
+			continue;
+		++*pos;
+		return ptr;
+	}
+
+	return NULL;
+}
+
+static void swap_stop(struct seq_file *swap, void *v)
+{
+	up(&swapon_sem);
+}
+
+static int swap_show(struct seq_file *swap, void *v)
+{
+	struct swap_info_struct *ptr = v;
+	struct file *file;
+	int len;
+
+	if (v == swap_info)
+		seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
+
+	file = ptr->swap_file;
+	len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
+	seq_printf(swap, "%*s%s\t%d\t%ld\t%d\n",
+		       len < 40 ? 40 - len : 1, " ",
+		       S_ISBLK(file->f_dentry->d_inode->i_mode) ?
+				"partition" : "file\t",
+		       ptr->pages << (PAGE_SHIFT - 10),
+		       ptr->inuse_pages << (PAGE_SHIFT - 10),
+		       ptr->prio);
+	return 0;
+}
+
+static struct seq_operations swaps_op = {
+	.start =	swap_start,
+	.next =		swap_next,
+	.stop =		swap_stop,
+	.show =		swap_show
+};
+
+static int swaps_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &swaps_op);
+}
+
+static struct file_operations proc_swaps_operations = {
+	.open		= swaps_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
+static int __init procswaps_init(void)
+{
+	struct proc_dir_entry *entry;
+
+	entry = create_proc_entry("swaps", 0, NULL);
+	if (entry)
+		entry->proc_fops = &proc_swaps_operations;
+	return 0;
+}
+__initcall(procswaps_init);
+#endif /* CONFIG_PROC_FS */
+
+/*
+ * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
+ *
+ * The swapon system call
+ */
+asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
+{
+	struct swap_info_struct * p;
+	char *name = NULL;
+	struct block_device *bdev = NULL;
+	struct file *swap_file = NULL;
+	struct address_space *mapping;
+	unsigned int type;
+	int i, prev;
+	int error;
+	static int least_priority;
+	union swap_header *swap_header = NULL;
+	int swap_header_version;
+	int nr_good_pages = 0;
+	unsigned long maxpages = 1;
+	int swapfilesize;
+	unsigned short *swap_map;
+	struct page *page = NULL;
+	struct inode *inode = NULL;
+	int did_down = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	swap_list_lock();
+	p = swap_info;
+	for (type = 0 ; type < nr_swapfiles ; type++,p++)
+		if (!(p->flags & SWP_USED))
+			break;
+	error = -EPERM;
+	/*
+	 * Test if adding another swap device is possible. There are
+	 * two limiting factors: 1) the number of bits for the swap
+	 * type swp_entry_t definition and 2) the number of bits for
+	 * the swap type in the swap ptes as defined by the different
+	 * architectures. To honor both limitations a swap entry
+	 * with swap offset 0 and swap type ~0UL is created, encoded
+	 * to a swap pte, decoded to a swp_entry_t again and finally
+	 * the swap type part is extracted. This will mask all bits
+	 * from the initial ~0UL that can't be encoded in either the
+	 * swp_entry_t or the architecture definition of a swap pte.
+	 */
+	if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
+		swap_list_unlock();
+		goto out;
+	}
+	if (type >= nr_swapfiles)
+		nr_swapfiles = type+1;
+	INIT_LIST_HEAD(&p->extent_list);
+	p->flags = SWP_USED;
+	p->nr_extents = 0;
+	p->swap_file = NULL;
+	p->old_block_size = 0;
+	p->swap_map = NULL;
+	p->lowest_bit = 0;
+	p->highest_bit = 0;
+	p->cluster_nr = 0;
+	p->inuse_pages = 0;
+	spin_lock_init(&p->sdev_lock);
+	p->next = -1;
+	if (swap_flags & SWAP_FLAG_PREFER) {
+		p->prio =
+		  (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
+	} else {
+		p->prio = --least_priority;
+	}
+	swap_list_unlock();
+	name = getname(specialfile);
+	error = PTR_ERR(name);
+	if (IS_ERR(name)) {
+		name = NULL;
+		goto bad_swap_2;
+	}
+	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
+	error = PTR_ERR(swap_file);
+	if (IS_ERR(swap_file)) {
+		swap_file = NULL;
+		goto bad_swap_2;
+	}
+
+	p->swap_file = swap_file;
+	mapping = swap_file->f_mapping;
+	inode = mapping->host;
+
+	error = -EBUSY;
+	for (i = 0; i < nr_swapfiles; i++) {
+		struct swap_info_struct *q = &swap_info[i];
+
+		if (i == type || !q->swap_file)
+			continue;
+		if (mapping == q->swap_file->f_mapping)
+			goto bad_swap;
+	}
+
+	error = -EINVAL;
+	if (S_ISBLK(inode->i_mode)) {
+		bdev = I_BDEV(inode);
+		error = bd_claim(bdev, sys_swapon);
+		if (error < 0) {
+			bdev = NULL;
+			goto bad_swap;
+		}
+		p->old_block_size = block_size(bdev);
+		error = set_blocksize(bdev, PAGE_SIZE);
+		if (error < 0)
+			goto bad_swap;
+		p->bdev = bdev;
+	} else if (S_ISREG(inode->i_mode)) {
+		p->bdev = inode->i_sb->s_bdev;
+		down(&inode->i_sem);
+		did_down = 1;
+		if (IS_SWAPFILE(inode)) {
+			error = -EBUSY;
+			goto bad_swap;
+		}
+	} else {
+		goto bad_swap;
+	}
+
+	swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
+
+	/*
+	 * Read the swap header.
+	 */
+	if (!mapping->a_ops->readpage) {
+		error = -EINVAL;
+		goto bad_swap;
+	}
+	page = read_cache_page(mapping, 0,
+			(filler_t *)mapping->a_ops->readpage, swap_file);
+	if (IS_ERR(page)) {
+		error = PTR_ERR(page);
+		goto bad_swap;
+	}
+	wait_on_page_locked(page);
+	if (!PageUptodate(page))
+		goto bad_swap;
+	kmap(page);
+	swap_header = page_address(page);
+
+	if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
+		swap_header_version = 1;
+	else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
+		swap_header_version = 2;
+	else {
+		printk("Unable to find swap-space signature\n");
+		error = -EINVAL;
+		goto bad_swap;
+	}
+	
+	switch (swap_header_version) {
+	case 1:
+		printk(KERN_ERR "version 0 swap is no longer supported. "
+			"Use mkswap -v1 %s\n", name);
+		error = -EINVAL;
+		goto bad_swap;
+	case 2:
+		/* Check the swap header's sub-version and the size of
+                   the swap file and bad block lists */
+		if (swap_header->info.version != 1) {
+			printk(KERN_WARNING
+			       "Unable to handle swap header version %d\n",
+			       swap_header->info.version);
+			error = -EINVAL;
+			goto bad_swap;
+		}
+
+		p->lowest_bit  = 1;
+		/*
+		 * Find out how many pages are allowed for a single swap
+		 * device. There are two limiting factors: 1) the number of
+		 * bits for the swap offset in the swp_entry_t type and
+		 * 2) the number of bits in the a swap pte as defined by
+		 * the different architectures. In order to find the
+		 * largest possible bit mask a swap entry with swap type 0
+		 * and swap offset ~0UL is created, encoded to a swap pte,
+		 * decoded to a swp_entry_t again and finally the swap
+		 * offset is extracted. This will mask all the bits from
+		 * the initial ~0UL mask that can't be encoded in either
+		 * the swp_entry_t or the architecture definition of a
+		 * swap pte.
+		 */
+		maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
+		if (maxpages > swap_header->info.last_page)
+			maxpages = swap_header->info.last_page;
+		p->highest_bit = maxpages - 1;
+
+		error = -EINVAL;
+		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+			goto bad_swap;
+		
+		/* OK, set up the swap map and apply the bad block list */
+		if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
+			error = -ENOMEM;
+			goto bad_swap;
+		}
+
+		error = 0;
+		memset(p->swap_map, 0, maxpages * sizeof(short));
+		for (i=0; i<swap_header->info.nr_badpages; i++) {
+			int page = swap_header->info.badpages[i];
+			if (page <= 0 || page >= swap_header->info.last_page)
+				error = -EINVAL;
+			else
+				p->swap_map[page] = SWAP_MAP_BAD;
+		}
+		nr_good_pages = swap_header->info.last_page -
+				swap_header->info.nr_badpages -
+				1 /* header page */;
+		if (error) 
+			goto bad_swap;
+	}
+	
+	if (swapfilesize && maxpages > swapfilesize) {
+		printk(KERN_WARNING
+		       "Swap area shorter than signature indicates\n");
+		error = -EINVAL;
+		goto bad_swap;
+	}
+	if (!nr_good_pages) {
+		printk(KERN_WARNING "Empty swap-file\n");
+		error = -EINVAL;
+		goto bad_swap;
+	}
+	p->swap_map[0] = SWAP_MAP_BAD;
+	p->max = maxpages;
+	p->pages = nr_good_pages;
+
+	error = setup_swap_extents(p);
+	if (error)
+		goto bad_swap;
+
+	down(&swapon_sem);
+	swap_list_lock();
+	swap_device_lock(p);
+	p->flags = SWP_ACTIVE;
+	nr_swap_pages += nr_good_pages;
+	total_swap_pages += nr_good_pages;
+	printk(KERN_INFO "Adding %dk swap on %s.  Priority:%d extents:%d\n",
+		nr_good_pages<<(PAGE_SHIFT-10), name,
+		p->prio, p->nr_extents);
+
+	/* insert swap space into swap_list: */
+	prev = -1;
+	for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
+		if (p->prio >= swap_info[i].prio) {
+			break;
+		}
+		prev = i;
+	}
+	p->next = i;
+	if (prev < 0) {
+		swap_list.head = swap_list.next = p - swap_info;
+	} else {
+		swap_info[prev].next = p - swap_info;
+	}
+	swap_device_unlock(p);
+	swap_list_unlock();
+	up(&swapon_sem);
+	error = 0;
+	goto out;
+bad_swap:
+	if (bdev) {
+		set_blocksize(bdev, p->old_block_size);
+		bd_release(bdev);
+	}
+bad_swap_2:
+	swap_list_lock();
+	swap_map = p->swap_map;
+	p->swap_file = NULL;
+	p->swap_map = NULL;
+	p->flags = 0;
+	if (!(swap_flags & SWAP_FLAG_PREFER))
+		++least_priority;
+	swap_list_unlock();
+	destroy_swap_extents(p);
+	vfree(swap_map);
+	if (swap_file)
+		filp_close(swap_file, NULL);
+out:
+	if (page && !IS_ERR(page)) {
+		kunmap(page);
+		page_cache_release(page);
+	}
+	if (name)
+		putname(name);
+	if (did_down) {
+		if (!error)
+			inode->i_flags |= S_SWAPFILE;
+		up(&inode->i_sem);
+	}
+	return error;
+}
+
+void si_swapinfo(struct sysinfo *val)
+{
+	unsigned int i;
+	unsigned long nr_to_be_unused = 0;
+
+	swap_list_lock();
+	for (i = 0; i < nr_swapfiles; i++) {
+		if (!(swap_info[i].flags & SWP_USED) ||
+		     (swap_info[i].flags & SWP_WRITEOK))
+			continue;
+		nr_to_be_unused += swap_info[i].inuse_pages;
+	}
+	val->freeswap = nr_swap_pages + nr_to_be_unused;
+	val->totalswap = total_swap_pages + nr_to_be_unused;
+	swap_list_unlock();
+}
+
+/*
+ * Verify that a swap entry is valid and increment its swap map count.
+ *
+ * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
+ * "permanent", but will be reclaimed by the next swapoff.
+ */
+int swap_duplicate(swp_entry_t entry)
+{
+	struct swap_info_struct * p;
+	unsigned long offset, type;
+	int result = 0;
+
+	type = swp_type(entry);
+	if (type >= nr_swapfiles)
+		goto bad_file;
+	p = type + swap_info;
+	offset = swp_offset(entry);
+
+	swap_device_lock(p);
+	if (offset < p->max && p->swap_map[offset]) {
+		if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
+			p->swap_map[offset]++;
+			result = 1;
+		} else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
+			if (swap_overflow++ < 5)
+				printk(KERN_WARNING "swap_dup: swap entry overflow\n");
+			p->swap_map[offset] = SWAP_MAP_MAX;
+			result = 1;
+		}
+	}
+	swap_device_unlock(p);
+out:
+	return result;
+
+bad_file:
+	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
+	goto out;
+}
+
+struct swap_info_struct *
+get_swap_info_struct(unsigned type)
+{
+	return &swap_info[type];
+}
+
+/*
+ * swap_device_lock prevents swap_map being freed. Don't grab an extra
+ * reference on the swaphandle, it doesn't matter if it becomes unused.
+ */
+int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
+{
+	int ret = 0, i = 1 << page_cluster;
+	unsigned long toff;
+	struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
+
+	if (!page_cluster)	/* no readahead */
+		return 0;
+	toff = (swp_offset(entry) >> page_cluster) << page_cluster;
+	if (!toff)		/* first page is swap header */
+		toff++, i--;
+	*offset = toff;
+
+	swap_device_lock(swapdev);
+	do {
+		/* Don't read-ahead past the end of the swap area */
+		if (toff >= swapdev->max)
+			break;
+		/* Don't read in free or bad pages */
+		if (!swapdev->swap_map[toff])
+			break;
+		if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
+			break;
+		toff++;
+		ret++;
+	} while (--i);
+	swap_device_unlock(swapdev);
+	return ret;
+}