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