#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. */ 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 (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; } /* * 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 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 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_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; } 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); /* * 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); } 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 */