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67f9fd91f9
This patch removes read_cache_page_async() which wasn't really needed anywhere and simplifies the code around it a bit. read_cache_page_async() is useful when we want to read a page into the cache without waiting for it to complete. This happens when the appropriate callback 'filler' doesn't complete its read operation and releases the page lock immediately, and instead queues a different completion routine to do that. This never actually happened anywhere in the code. read_cache_page_async() had 3 different callers: - read_cache_page() which is the sync version, it would just wait for the requested read to complete using wait_on_page_read(). - JFFS2 would call it from jffs2_gc_fetch_page(), but the filler function it supplied doesn't do any async reads, and would complete before the filler function returns - making it actually a sync read. - CRAMFS would call it using the read_mapping_page_async() wrapper, with a similar story to JFFS2 - the filler function doesn't do anything that reminds async reads and would always complete before the filler function returns. To sum it up, the code in mm/filemap.c never took advantage of having read_cache_page_async(). While there are filler callbacks that do async reads (such as the block one), we always called it with the read_cache_page(). This patch adds a mandatory wait for read to complete when adding a new page to the cache, and removes read_cache_page_async() and its wrappers. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
571 lines
16 KiB
C
571 lines
16 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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AS_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */
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AS_EXITING = __GFP_BITS_SHIFT + 5, /* final truncate in progress */
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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 (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 void mapping_set_balloon(struct address_space *mapping)
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{
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set_bit(AS_BALLOON_MAP, &mapping->flags);
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}
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static inline void mapping_clear_balloon(struct address_space *mapping)
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{
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clear_bit(AS_BALLOON_MAP, &mapping->flags);
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}
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static inline int mapping_balloon(struct address_space *mapping)
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{
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return mapping && test_bit(AS_BALLOON_MAP, &mapping->flags);
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}
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static inline void mapping_set_exiting(struct address_space *mapping)
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{
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set_bit(AS_EXITING, &mapping->flags);
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}
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static inline int mapping_exiting(struct address_space *mapping)
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{
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return test_bit(AS_EXITING, &mapping->flags);
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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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#ifdef CONFIG_TINY_RCU
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# ifdef CONFIG_PREEMPT_COUNT
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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(page_count(page) == 0, page);
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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_PAGE(PageTail(page), 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_COUNT
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VM_BUG_ON(!in_atomic());
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# endif
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VM_BUG_ON_PAGE(page_count(page) == 0, page);
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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_PAGE(PageCompound(page) && page != compound_head(page), 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(page_count(page) != 0, page);
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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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static inline struct page *page_cache_alloc_readahead(struct address_space *x)
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{
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return __page_cache_alloc(mapping_gfp_mask(x) |
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__GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
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}
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typedef int filler_t(void *, struct page *);
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pgoff_t page_cache_next_hole(struct address_space *mapping,
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pgoff_t index, unsigned long max_scan);
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pgoff_t page_cache_prev_hole(struct address_space *mapping,
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pgoff_t index, unsigned long max_scan);
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struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
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struct page *find_get_page(struct address_space *mapping, pgoff_t offset);
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struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
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struct page *find_lock_page(struct address_space *mapping, pgoff_t offset);
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struct page *find_or_create_page(struct address_space *mapping, pgoff_t index,
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gfp_t gfp_mask);
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unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
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unsigned int nr_entries, struct page **entries,
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pgoff_t *indices);
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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(struct address_space *mapping,
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pgoff_t index, filler_t *filler, 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(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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static inline loff_t page_file_offset(struct page *page)
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{
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return ((loff_t)page_file_index(page)) << 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 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_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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extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
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static inline int wait_on_page_locked_killable(struct page *page)
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{
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if (PageLocked(page))
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return wait_on_page_bit_killable(page, PG_locked);
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return 0;
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}
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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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void wait_for_stable_page(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;
|
|
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Multipage variants of the above prefault helpers, useful if more than
|
|
* PAGE_SIZE of data needs to be prefaulted. These are separate from the above
|
|
* functions (which only handle up to PAGE_SIZE) to avoid clobbering the
|
|
* filemap.c hotpaths.
|
|
*/
|
|
static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
|
|
{
|
|
int ret = 0;
|
|
char __user *end = uaddr + size - 1;
|
|
|
|
if (unlikely(size == 0))
|
|
return ret;
|
|
|
|
/*
|
|
* Writing zeroes into userspace here is OK, because we know that if
|
|
* the zero gets there, we'll be overwriting it.
|
|
*/
|
|
while (uaddr <= end) {
|
|
ret = __put_user(0, uaddr);
|
|
if (ret != 0)
|
|
return ret;
|
|
uaddr += PAGE_SIZE;
|
|
}
|
|
|
|
/* Check whether the range spilled into the next page. */
|
|
if (((unsigned long)uaddr & PAGE_MASK) ==
|
|
((unsigned long)end & PAGE_MASK))
|
|
ret = __put_user(0, end);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static inline int fault_in_multipages_readable(const char __user *uaddr,
|
|
int size)
|
|
{
|
|
volatile char c;
|
|
int ret = 0;
|
|
const char __user *end = uaddr + size - 1;
|
|
|
|
if (unlikely(size == 0))
|
|
return ret;
|
|
|
|
while (uaddr <= end) {
|
|
ret = __get_user(c, uaddr);
|
|
if (ret != 0)
|
|
return ret;
|
|
uaddr += PAGE_SIZE;
|
|
}
|
|
|
|
/* Check whether the range spilled into the next page. */
|
|
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, void *shadow);
|
|
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 */
|