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![Michal Hocko](/assets/img/avatar_default.png)
Commit 2457aec637
("mm: non-atomically mark page accessed during page
cache allocation where possible") has added a separate parameter for
specifying gfp mask for radix tree allocations.
Not only this is less than optimal from the API point of view because it
is error prone, it is also buggy currently because
grab_cache_page_write_begin is using GFP_KERNEL for radix tree and if
fgp_flags doesn't contain FGP_NOFS (mostly controlled by fs by
AOP_FLAG_NOFS flag) but the mapping_gfp_mask has __GFP_FS cleared then
the radix tree allocation wouldn't obey the restriction and might
recurse into filesystem and cause deadlocks. This is the case for most
filesystems unfortunately because only ext4 and gfs2 are using
AOP_FLAG_NOFS.
Let's simply remove radix_gfp_mask parameter because the allocation
context is same for both page cache and for the radix tree. Just make
sure that the radix tree gets only the sane subset of the mask (e.g. do
not pass __GFP_WRITE).
Long term it is more preferable to convert remaining users of
AOP_FLAG_NOFS to use mapping_gfp_mask instead and simplify this
interface even further.
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
673 lines
19 KiB
C
673 lines
19 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_EXITING = __GFP_BITS_SHIFT + 4, /* 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_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 be 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, bool 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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#define FGP_ACCESSED 0x00000001
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#define FGP_LOCK 0x00000002
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#define FGP_CREAT 0x00000004
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#define FGP_WRITE 0x00000008
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#define FGP_NOFS 0x00000010
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#define FGP_NOWAIT 0x00000020
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struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
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int fgp_flags, gfp_t cache_gfp_mask);
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/**
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* find_get_page - find and get a page reference
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* @mapping: the address_space to search
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* @offset: the page index
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*
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* Looks up the page cache slot at @mapping & @offset. If there is a
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* page cache page, it is returned with an increased refcount.
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*
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* Otherwise, %NULL is returned.
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*/
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static inline struct page *find_get_page(struct address_space *mapping,
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pgoff_t offset)
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{
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return pagecache_get_page(mapping, offset, 0, 0);
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}
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static inline struct page *find_get_page_flags(struct address_space *mapping,
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pgoff_t offset, int fgp_flags)
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{
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return pagecache_get_page(mapping, offset, fgp_flags, 0);
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}
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/**
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* find_lock_page - locate, pin and lock a pagecache page
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* pagecache_get_page - find and get a page reference
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* @mapping: the address_space to search
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* @offset: the page index
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*
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* Looks up the page cache slot at @mapping & @offset. If there is a
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* page cache page, it is returned locked and with an increased
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* refcount.
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*
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* Otherwise, %NULL is returned.
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*
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* find_lock_page() may sleep.
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*/
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static inline struct page *find_lock_page(struct address_space *mapping,
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pgoff_t offset)
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{
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return pagecache_get_page(mapping, offset, FGP_LOCK, 0);
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}
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/**
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* find_or_create_page - locate or add a pagecache page
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* @mapping: the page's address_space
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* @index: the page's index into the mapping
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* @gfp_mask: page allocation mode
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*
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* Looks up the page cache slot at @mapping & @offset. If there is a
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* page cache page, it is returned locked and with an increased
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* refcount.
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*
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* If the page is not present, a new page is allocated using @gfp_mask
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* and added to the page cache and the VM's LRU list. The page is
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* returned locked and with an increased refcount.
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*
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* On memory exhaustion, %NULL is returned.
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*
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* find_or_create_page() may sleep, even if @gfp_flags specifies an
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* atomic allocation!
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*/
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static inline struct page *find_or_create_page(struct address_space *mapping,
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pgoff_t offset, gfp_t gfp_mask)
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{
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return pagecache_get_page(mapping, offset,
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FGP_LOCK|FGP_ACCESSED|FGP_CREAT,
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gfp_mask);
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}
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/**
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* grab_cache_page_nowait - returns locked page at given index in given cache
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* @mapping: target address_space
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* @index: the page index
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*
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* Same as grab_cache_page(), but do not wait if the page is unavailable.
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* This is intended for speculative data generators, where the data can
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* be regenerated if the page couldn't be grabbed. This routine should
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* be safe to call while holding the lock for another page.
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*
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* Clear __GFP_FS when allocating the page to avoid recursion into the fs
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* and deadlock against the caller's locked page.
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*/
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static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
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pgoff_t index)
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{
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return pagecache_get_page(mapping, index,
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FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
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mapping_gfp_mask(mapping));
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}
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struct page *find_get_entry(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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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 * 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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* Get the offset in PAGE_SIZE.
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* (TODO: hugepage should have ->index in PAGE_SIZE)
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*/
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static inline pgoff_t page_to_pgoff(struct page *page)
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{
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if (unlikely(PageHeadHuge(page)))
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return page->index << compound_order(page);
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else
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return page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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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))
|
|
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.
|
|
*
|
|
* Return value and mmap_sem implications depend on flags; see
|
|
* __lock_page_or_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,
|
|
* and for filesystems which need to wait on PG_private.
|
|
*/
|
|
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);
|
|
extern int wait_on_page_bit_killable_timeout(struct page *page,
|
|
int bit_nr, unsigned long timeout);
|
|
|
|
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;
|
|
}
|
|
|
|
extern wait_queue_head_t *page_waitqueue(struct page *page);
|
|
static inline void wake_up_page(struct page *page, int bit)
|
|
{
|
|
__wake_up_bit(page_waitqueue(page), &page->flags, bit);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
void wait_for_stable_page(struct page *page);
|
|
|
|
void page_endio(struct page *page, int rw, int err);
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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 */
|