#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 */
+enum mapping_flags {
+ AS_EIO = __GFP_BITS_SHIFT + 0, /* IO error on async write */
+ AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
+ AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
+ AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
+};
static inline void mapping_set_error(struct address_space *mapping, int error)
{
- if (error) {
+ if (unlikely(error)) {
if (error == -ENOSPC)
set_bit(AS_ENOSPC, &mapping->flags);
else
}
}
+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;
+}
+
static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
#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_TREE_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_TREE_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
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);
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags);
/*
* Returns locked page at given index in given cache, creating it if needed.
extern struct page * read_cache_page(struct address_space *mapping,
pgoff_t index, filler_t *filler,
void *data);
+extern struct page * read_cache_page_gfp(struct address_space *mapping,
+ pgoff_t index, gfp_t gfp_mask);
extern int read_cache_pages(struct address_space *mapping,
struct list_head *pages, filler_t *filler, void *data);
return read_cache_page(mapping, index, filler, data);
}
-int add_to_page_cache(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);
-
/*
* Return byte-offset into filesystem object for 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 (TestSetPageLocked(page))
+ if (!trylock_page(page))
__lock_page(page);
}
static inline int lock_page_killable(struct page *page)
{
might_sleep();
- if (TestSetPageLocked(page))
+ if (!trylock_page(page))
return __lock_page_killable(page);
return 0;
}
static inline void lock_page_nosync(struct page *page)
{
might_sleep();
- if (TestSetPageLocked(page))
+ if (!trylock_page(page))
__lock_page_nosync(page);
}
extern void end_page_writeback(struct page *page);
/*
+ * Add an arbitrary waiter to a page's wait queue
+ */
+extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
+
+/*
* Fault a userspace page into pagetables. Return non-zero on a fault.
*
* This assumes that two userspace pages are always sufficient. That's
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 */
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff