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Diffstat (limited to 'include/linux/pagemap.h')
| -rw-r--r-- | include/linux/pagemap.h | 479 |
1 files changed, 479 insertions, 0 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h new file mode 100644 index 00000000..cfaaa694 --- /dev/null +++ b/include/linux/pagemap.h @@ -0,0 +1,479 @@ +#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() */ +#include <linux/hugetlb_inline.h> + +/* + * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page + * allocation mode flags. + */ +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 (unlikely(error)) { + if (error == -ENOSPC) + set_bit(AS_ENOSPC, &mapping->flags); + else + set_bit(AS_EIO, &mapping->flags); + } +} + +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 (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; +} + +/* + * 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_TREE_RCU) +# ifdef CONFIG_PREEMPT_COUNT + 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_COUNT + 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); +} + +static inline struct page *page_cache_alloc_readahead(struct address_space *x) +{ + return __page_cache_alloc(mapping_gfp_mask(x) | + __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN); +} + +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_write_begin(struct address_space *mapping, + pgoff_t index, unsigned flags); + +/* + * 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 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); + +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; +} + +extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma, + unsigned long address); + +static inline pgoff_t linear_page_index(struct vm_area_struct *vma, + unsigned long address) +{ + pgoff_t pgoff; + if (unlikely(is_vm_hugetlb_page(vma))) + return linear_hugepage_index(vma, address); + 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 int __lock_page_or_retry(struct page *page, struct mm_struct *mm, + unsigned int flags); +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_or_retry - Lock the page, unless this would block and the + * caller indicated that it can handle a retry. + */ +static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm, + unsigned int flags) +{ + might_sleep(); + return trylock_page(page) || __lock_page_or_retry(page, mm, flags); +} + +/* + * 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); + +extern int wait_on_page_bit_killable(struct page *page, int bit_nr); + +static inline int wait_on_page_locked_killable(struct page *page) +{ + if (PageLocked(page)) + return wait_on_page_bit_killable(page, PG_locked); + return 0; +} + +/* + * 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); + +/* + * 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 + * 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); + (void)c; + } + } + 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 delete_from_page_cache(struct page *page); +extern void __delete_from_page_cache(struct page *page); +int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask); + +/* + * 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 */ |