--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/linux/pagemap.h	Sun Jan 11 20:20:11 2009 +0100
@@ -0,0 +1,455 @@
+#ifndef _LINUX_PAGEMAP_H
+#define _LINUX_PAGEMAP_H
+
+/*
+ * Copyright 1995 Linus Torvalds
+ */
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+#include <linux/compiler.h>
+#include <asm/uaccess.h>
+#include <linux/gfp.h>
+#include <linux/bitops.h>
+#include <linux/hardirq.h> /* for in_interrupt() */
+
+/*
+ * Bits in mapping->flags.  The lower __GFP_BITS_SHIFT bits are the page
+ * allocation mode flags.
+ */
+#define	AS_EIO		(__GFP_BITS_SHIFT + 0)	/* IO error on async write */
+#define AS_ENOSPC	(__GFP_BITS_SHIFT + 1)	/* ENOSPC on async write */
+#define AS_MM_ALL_LOCKS	(__GFP_BITS_SHIFT + 2)	/* under mm_take_all_locks() */
+
+static inline void mapping_set_error(struct address_space *mapping, int error)
+{
+	if (unlikely(error)) {
+		if (error == -ENOSPC)
+			set_bit(AS_ENOSPC, &mapping->flags);
+		else
+			set_bit(AS_EIO, &mapping->flags);
+	}
+}
+
+#ifdef CONFIG_UNEVICTABLE_LRU
+#define AS_UNEVICTABLE	(__GFP_BITS_SHIFT + 2)	/* e.g., ramdisk, SHM_LOCK */
+
+static inline void mapping_set_unevictable(struct address_space *mapping)
+{
+	set_bit(AS_UNEVICTABLE, &mapping->flags);
+}
+
+static inline void mapping_clear_unevictable(struct address_space *mapping)
+{
+	clear_bit(AS_UNEVICTABLE, &mapping->flags);
+}
+
+static inline int mapping_unevictable(struct address_space *mapping)
+{
+	if (likely(mapping))
+		return test_bit(AS_UNEVICTABLE, &mapping->flags);
+	return !!mapping;
+}
+#else
+static inline void mapping_set_unevictable(struct address_space *mapping) { }
+static inline void mapping_clear_unevictable(struct address_space *mapping) { }
+static inline int mapping_unevictable(struct address_space *mapping)
+{
+	return 0;
+}
+#endif
+
+static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
+{
+	return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
+}
+
+/*
+ * This is non-atomic.  Only to be used before the mapping is activated.
+ * Probably needs a barrier...
+ */
+static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
+{
+	m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
+				(__force unsigned long)mask;
+}
+
+/*
+ * The page cache can done in larger chunks than
+ * one page, because it allows for more efficient
+ * throughput (it can then be mapped into user
+ * space in smaller chunks for same flexibility).
+ *
+ * Or rather, it _will_ be done in larger chunks.
+ */
+#define PAGE_CACHE_SHIFT	PAGE_SHIFT
+#define PAGE_CACHE_SIZE		PAGE_SIZE
+#define PAGE_CACHE_MASK		PAGE_MASK
+#define PAGE_CACHE_ALIGN(addr)	(((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
+
+#define page_cache_get(page)		get_page(page)
+#define page_cache_release(page)	put_page(page)
+void release_pages(struct page **pages, int nr, int cold);
+
+/*
+ * speculatively take a reference to a page.
+ * If the page is free (_count == 0), then _count is untouched, and 0
+ * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
+ *
+ * This function must be called inside the same rcu_read_lock() section as has
+ * been used to lookup the page in the pagecache radix-tree (or page table):
+ * this allows allocators to use a synchronize_rcu() to stabilize _count.
+ *
+ * Unless an RCU grace period has passed, the count of all pages coming out
+ * of the allocator must be considered unstable. page_count may return higher
+ * than expected, and put_page must be able to do the right thing when the
+ * page has been finished with, no matter what it is subsequently allocated
+ * for (because put_page is what is used here to drop an invalid speculative
+ * reference).
+ *
+ * This is the interesting part of the lockless pagecache (and lockless
+ * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
+ * has the following pattern:
+ * 1. find page in radix tree
+ * 2. conditionally increment refcount
+ * 3. check the page is still in pagecache (if no, goto 1)
+ *
+ * Remove-side that cares about stability of _count (eg. reclaim) has the
+ * following (with tree_lock held for write):
+ * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
+ * B. remove page from pagecache
+ * C. free the page
+ *
+ * There are 2 critical interleavings that matter:
+ * - 2 runs before A: in this case, A sees elevated refcount and bails out
+ * - A runs before 2: in this case, 2 sees zero refcount and retries;
+ *   subsequently, B will complete and 1 will find no page, causing the
+ *   lookup to return NULL.
+ *
+ * It is possible that between 1 and 2, the page is removed then the exact same
+ * page is inserted into the same position in pagecache. That's OK: the
+ * old find_get_page using tree_lock could equally have run before or after
+ * such a re-insertion, depending on order that locks are granted.
+ *
+ * Lookups racing against pagecache insertion isn't a big problem: either 1
+ * will find the page or it will not. Likewise, the old find_get_page could run
+ * either before the insertion or afterwards, depending on timing.
+ */
+static inline int page_cache_get_speculative(struct page *page)
+{
+	VM_BUG_ON(in_interrupt());
+
+#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU)
+# ifdef CONFIG_PREEMPT
+	VM_BUG_ON(!in_atomic());
+# endif
+	/*
+	 * Preempt must be disabled here - we rely on rcu_read_lock doing
+	 * this for us.
+	 *
+	 * Pagecache won't be truncated from interrupt context, so if we have
+	 * found a page in the radix tree here, we have pinned its refcount by
+	 * disabling preempt, and hence no need for the "speculative get" that
+	 * SMP requires.
+	 */
+	VM_BUG_ON(page_count(page) == 0);
+	atomic_inc(&page->_count);
+
+#else
+	if (unlikely(!get_page_unless_zero(page))) {
+		/*
+		 * Either the page has been freed, or will be freed.
+		 * In either case, retry here and the caller should
+		 * do the right thing (see comments above).
+		 */
+		return 0;
+	}
+#endif
+	VM_BUG_ON(PageTail(page));
+
+	return 1;
+}
+
+/*
+ * Same as above, but add instead of inc (could just be merged)
+ */
+static inline int page_cache_add_speculative(struct page *page, int count)
+{
+	VM_BUG_ON(in_interrupt());
+
+#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU)
+# ifdef CONFIG_PREEMPT
+	VM_BUG_ON(!in_atomic());
+# endif
+	VM_BUG_ON(page_count(page) == 0);
+	atomic_add(count, &page->_count);
+
+#else
+	if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
+		return 0;
+#endif
+	VM_BUG_ON(PageCompound(page) && page != compound_head(page));
+
+	return 1;
+}
+
+static inline int page_freeze_refs(struct page *page, int count)
+{
+	return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
+}
+
+static inline void page_unfreeze_refs(struct page *page, int count)
+{
+	VM_BUG_ON(page_count(page) != 0);
+	VM_BUG_ON(count == 0);
+
+	atomic_set(&page->_count, count);
+}
+
+#ifdef CONFIG_NUMA
+extern struct page *__page_cache_alloc(gfp_t gfp);
+#else
+static inline struct page *__page_cache_alloc(gfp_t gfp)
+{
+	return alloc_pages(gfp, 0);
+}
+#endif
+
+static inline struct page *page_cache_alloc(struct address_space *x)
+{
+	return __page_cache_alloc(mapping_gfp_mask(x));
+}
+
+static inline struct page *page_cache_alloc_cold(struct address_space *x)
+{
+	return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
+}
+
+typedef int filler_t(void *, struct page *);
+
+extern struct page * find_get_page(struct address_space *mapping,
+				pgoff_t index);
+extern struct page * find_lock_page(struct address_space *mapping,
+				pgoff_t index);
+extern struct page * find_or_create_page(struct address_space *mapping,
+				pgoff_t index, gfp_t gfp_mask);
+unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
+			unsigned int nr_pages, struct page **pages);
+unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
+			       unsigned int nr_pages, struct page **pages);
+unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
+			int tag, unsigned int nr_pages, struct page **pages);
+
+struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index);
+
+/*
+ * Returns locked page at given index in given cache, creating it if needed.
+ */
+static inline struct page *grab_cache_page(struct address_space *mapping,
+								pgoff_t index)
+{
+	return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
+}
+
+extern struct page * grab_cache_page_nowait(struct address_space *mapping,
+				pgoff_t index);
+extern struct page * read_cache_page_async(struct address_space *mapping,
+				pgoff_t index, filler_t *filler,
+				void *data);
+extern struct page * read_cache_page(struct address_space *mapping,
+				pgoff_t index, filler_t *filler,
+				void *data);
+extern int read_cache_pages(struct address_space *mapping,
+		struct list_head *pages, filler_t *filler, void *data);
+
+static inline struct page *read_mapping_page_async(
+						struct address_space *mapping,
+						     pgoff_t index, void *data)
+{
+	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
+	return read_cache_page_async(mapping, index, filler, data);
+}
+
+static inline struct page *read_mapping_page(struct address_space *mapping,
+					     pgoff_t index, void *data)
+{
+	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
+	return read_cache_page(mapping, index, filler, data);
+}
+
+/*
+ * Return byte-offset into filesystem object for page.
+ */
+static inline loff_t page_offset(struct page *page)
+{
+	return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
+}
+
+static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
+					unsigned long address)
+{
+	pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
+	pgoff += vma->vm_pgoff;
+	return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+}
+
+extern void __lock_page(struct page *page);
+extern int __lock_page_killable(struct page *page);
+extern void __lock_page_nosync(struct page *page);
+extern void unlock_page(struct page *page);
+
+static inline void __set_page_locked(struct page *page)
+{
+	__set_bit(PG_locked, &page->flags);
+}
+
+static inline void __clear_page_locked(struct page *page)
+{
+	__clear_bit(PG_locked, &page->flags);
+}
+
+static inline int trylock_page(struct page *page)
+{
+	return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
+}
+
+/*
+ * lock_page may only be called if we have the page's inode pinned.
+ */
+static inline void lock_page(struct page *page)
+{
+	might_sleep();
+	if (!trylock_page(page))
+		__lock_page(page);
+}
+
+/*
+ * lock_page_killable is like lock_page but can be interrupted by fatal
+ * signals.  It returns 0 if it locked the page and -EINTR if it was
+ * killed while waiting.
+ */
+static inline int lock_page_killable(struct page *page)
+{
+	might_sleep();
+	if (!trylock_page(page))
+		return __lock_page_killable(page);
+	return 0;
+}
+
+/*
+ * lock_page_nosync should only be used if we can't pin the page's inode.
+ * Doesn't play quite so well with block device plugging.
+ */
+static inline void lock_page_nosync(struct page *page)
+{
+	might_sleep();
+	if (!trylock_page(page))
+		__lock_page_nosync(page);
+}
+	
+/*
+ * This is exported only for wait_on_page_locked/wait_on_page_writeback.
+ * Never use this directly!
+ */
+extern void wait_on_page_bit(struct page *page, int bit_nr);
+
+/* 
+ * Wait for a page to be unlocked.
+ *
+ * This must be called with the caller "holding" the page,
+ * ie with increased "page->count" so that the page won't
+ * go away during the wait..
+ */
+static inline void wait_on_page_locked(struct page *page)
+{
+	if (PageLocked(page))
+		wait_on_page_bit(page, PG_locked);
+}
+
+/* 
+ * Wait for a page to complete writeback
+ */
+static inline void wait_on_page_writeback(struct page *page)
+{
+	if (PageWriteback(page))
+		wait_on_page_bit(page, PG_writeback);
+}
+
+extern void end_page_writeback(struct page *page);
+
+/*
+ * Fault a userspace page into pagetables.  Return non-zero on a fault.
+ *
+ * This assumes that two userspace pages are always sufficient.  That's
+ * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
+ */
+static inline int fault_in_pages_writeable(char __user *uaddr, int size)
+{
+	int ret;
+
+	if (unlikely(size == 0))
+		return 0;
+
+	/*
+	 * Writing zeroes into userspace here is OK, because we know that if
+	 * the zero gets there, we'll be overwriting it.
+	 */
+	ret = __put_user(0, uaddr);
+	if (ret == 0) {
+		char __user *end = uaddr + size - 1;
+
+		/*
+		 * If the page was already mapped, this will get a cache miss
+		 * for sure, so try to avoid doing it.
+		 */
+		if (((unsigned long)uaddr & PAGE_MASK) !=
+				((unsigned long)end & PAGE_MASK))
+		 	ret = __put_user(0, end);
+	}
+	return ret;
+}
+
+static inline int fault_in_pages_readable(const char __user *uaddr, int size)
+{
+	volatile char c;
+	int ret;
+
+	if (unlikely(size == 0))
+		return 0;
+
+	ret = __get_user(c, uaddr);
+	if (ret == 0) {
+		const char __user *end = uaddr + size - 1;
+
+		if (((unsigned long)uaddr & PAGE_MASK) !=
+				((unsigned long)end & PAGE_MASK))
+		 	ret = __get_user(c, end);
+	}
+	return ret;
+}
+
+int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
+				pgoff_t index, gfp_t gfp_mask);
+int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
+				pgoff_t index, gfp_t gfp_mask);
+extern void remove_from_page_cache(struct page *page);
+extern void __remove_from_page_cache(struct page *page);
+
+/*
+ * Like add_to_page_cache_locked, but used to add newly allocated pages:
+ * the page is new, so we can just run __set_page_locked() against it.
+ */
+static inline int add_to_page_cache(struct page *page,
+		struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
+{
+	int error;
+
+	__set_page_locked(page);
+	error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
+	if (unlikely(error))
+		__clear_page_locked(page);
+	return error;
+}
+
+#endif /* _LINUX_PAGEMAP_H */