/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef _LINUX_PAGEMAP_H
  #define _LINUX_PAGEMAP_H
  
  /*
   * Copyright 1995 Linus Torvalds
   */
  #include <linux/mm.h>
  #include <linux/fs.h>
  #include <linux/list.h>
  #include <linux/highmem.h>
  #include <linux/compiler.h>

  #include <linux/uaccess.h>

  #include <linux/gfp.h>

  #include <linux/bitops.h>

  #include <linux/hardirq.h> /* for in_interrupt() */

  #include <linux/hugetlb_inline.h>

  
  /*

   * Bits in mapping->flags.

   */

  enum mapping_flags {

  	AS_EIO		= 0,	/* IO error on async write */
  	AS_ENOSPC	= 1,	/* ENOSPC on async write */
  	AS_MM_ALL_LOCKS	= 2,	/* under mm_take_all_locks() */
  	AS_UNEVICTABLE	= 3,	/* e.g., ramdisk, SHM_LOCK */
  	AS_EXITING	= 4, 	/* final truncate in progress */

  	/* writeback related tags are not used */

  	AS_NO_WRITEBACK_TAGS = 5,

  };

  /**
   * mapping_set_error - record a writeback error in the address_space
   * @mapping - the mapping in which an error should be set
   * @error - the error to set in the mapping
   *
   * When writeback fails in some way, we must record that error so that
   * userspace can be informed when fsync and the like are called.  We endeavor
   * to report errors on any file that was open at the time of the error.  Some
   * internal callers also need to know when writeback errors have occurred.
   *
   * When a writeback error occurs, most filesystems will want to call
   * mapping_set_error to record the error in the mapping so that it can be
   * reported when the application calls fsync(2).
   */

  static inline void mapping_set_error(struct address_space *mapping, int error)
  {

  	if (likely(!error))
  		return;
  
  	/* Record in wb_err for checkers using errseq_t based tracking */
  	filemap_set_wb_err(mapping, error);
  
  	/* Record it in flags for now, for legacy callers */
  	if (error == -ENOSPC)
  		set_bit(AS_ENOSPC, &mapping->flags);
  	else
  		set_bit(AS_EIO, &mapping->flags);

  }

  static inline void mapping_set_unevictable(struct address_space *mapping)
  {
  	set_bit(AS_UNEVICTABLE, &mapping->flags);
  }

  static inline void mapping_clear_unevictable(struct address_space *mapping)
  {
  	clear_bit(AS_UNEVICTABLE, &mapping->flags);
  }

  static inline int mapping_unevictable(struct address_space *mapping)
  {

  	if (mapping)

  		return test_bit(AS_UNEVICTABLE, &mapping->flags);
  	return !!mapping;

  }

  static inline void mapping_set_exiting(struct address_space *mapping)
  {
  	set_bit(AS_EXITING, &mapping->flags);
  }
  
  static inline int mapping_exiting(struct address_space *mapping)
  {
  	return test_bit(AS_EXITING, &mapping->flags);
  }

  static inline void mapping_set_no_writeback_tags(struct address_space *mapping)
  {
  	set_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
  }
  
  static inline int mapping_use_writeback_tags(struct address_space *mapping)
  {
  	return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
  }

  static inline gfp_t mapping_gfp_mask(struct address_space * mapping)

  {

  	return mapping->gfp_mask;

  }

  /* Restricts the given gfp_mask to what the mapping allows. */
  static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
  		gfp_t gfp_mask)
  {
  	return mapping_gfp_mask(mapping) & gfp_mask;
  }

  /*
   * This is non-atomic.  Only to be used before the mapping is activated.
   * Probably needs a barrier...
   */

  static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)

  {

  	m->gfp_mask = mask;

  }

  void release_pages(struct page **pages, int nr, bool cold);

  /*
   * speculatively take a reference to a page.

   * If the page is free (_refcount == 0), then _refcount is untouched, and 0
   * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned.

   *
   * This function must be called inside the same rcu_read_lock() section as has
   * been used to lookup the page in the pagecache radix-tree (or page table):

   * this allows allocators to use a synchronize_rcu() to stabilize _refcount.

   *
   * Unless an RCU grace period has passed, the count of all pages coming out
   * of the allocator must be considered unstable. page_count may return higher
   * than expected, and put_page must be able to do the right thing when the
   * page has been finished with, no matter what it is subsequently allocated
   * for (because put_page is what is used here to drop an invalid speculative
   * reference).
   *
   * This is the interesting part of the lockless pagecache (and lockless
   * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
   * has the following pattern:
   * 1. find page in radix tree
   * 2. conditionally increment refcount
   * 3. check the page is still in pagecache (if no, goto 1)
   *

   * Remove-side that cares about stability of _refcount (eg. reclaim) has the

   * following (with tree_lock held for write):
   * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
   * B. remove page from pagecache
   * C. free the page
   *
   * There are 2 critical interleavings that matter:
   * - 2 runs before A: in this case, A sees elevated refcount and bails out
   * - A runs before 2: in this case, 2 sees zero refcount and retries;
   *   subsequently, B will complete and 1 will find no page, causing the
   *   lookup to return NULL.
   *
   * It is possible that between 1 and 2, the page is removed then the exact same
   * page is inserted into the same position in pagecache. That's OK: the
   * old find_get_page using tree_lock could equally have run before or after
   * such a re-insertion, depending on order that locks are granted.
   *
   * Lookups racing against pagecache insertion isn't a big problem: either 1
   * will find the page or it will not. Likewise, the old find_get_page could run
   * either before the insertion or afterwards, depending on timing.
   */
  static inline int page_cache_get_speculative(struct page *page)
  {

  #ifdef CONFIG_TINY_RCU

  # ifdef CONFIG_PREEMPT_COUNT

  	VM_BUG_ON(!in_atomic() && !irqs_disabled());

  # endif
  	/*
  	 * Preempt must be disabled here - we rely on rcu_read_lock doing
  	 * this for us.
  	 *
  	 * Pagecache won't be truncated from interrupt context, so if we have
  	 * found a page in the radix tree here, we have pinned its refcount by
  	 * disabling preempt, and hence no need for the "speculative get" that
  	 * SMP requires.
  	 */

  	VM_BUG_ON_PAGE(page_count(page) == 0, page);

  	page_ref_inc(page);

  
  #else
  	if (unlikely(!get_page_unless_zero(page))) {
  		/*
  		 * Either the page has been freed, or will be freed.
  		 * In either case, retry here and the caller should
  		 * do the right thing (see comments above).
  		 */
  		return 0;
  	}
  #endif

  	VM_BUG_ON_PAGE(PageTail(page), page);

  
  	return 1;
  }

  /*
   * Same as above, but add instead of inc (could just be merged)
   */
  static inline int page_cache_add_speculative(struct page *page, int count)
  {
  	VM_BUG_ON(in_interrupt());

  #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)

  # ifdef CONFIG_PREEMPT_COUNT

  	VM_BUG_ON(!in_atomic() && !irqs_disabled());

  # endif

  	VM_BUG_ON_PAGE(page_count(page) == 0, page);

  	page_ref_add(page, count);

  
  #else

  	if (unlikely(!page_ref_add_unless(page, count, 0)))

  		return 0;
  #endif

  	VM_BUG_ON_PAGE(PageCompound(page) && page != compound_head(page), page);

  
  	return 1;
  }

  #ifdef CONFIG_NUMA

  extern struct page *__page_cache_alloc(gfp_t gfp);

  #else

  static inline struct page *__page_cache_alloc(gfp_t gfp)
  {
  	return alloc_pages(gfp, 0);
  }
  #endif

  static inline struct page *page_cache_alloc(struct address_space *x)
  {

  	return __page_cache_alloc(mapping_gfp_mask(x));

  }
  
  static inline struct page *page_cache_alloc_cold(struct address_space *x)
  {

  	return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);

  }

  static inline gfp_t readahead_gfp_mask(struct address_space *x)

  {

  	return mapping_gfp_mask(x) |
  				  __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN;

  }

  typedef int filler_t(void *, struct page *);

  pgoff_t page_cache_next_hole(struct address_space *mapping,
  			     pgoff_t index, unsigned long max_scan);
  pgoff_t page_cache_prev_hole(struct address_space *mapping,
  			     pgoff_t index, unsigned long max_scan);

  #define FGP_ACCESSED		0x00000001
  #define FGP_LOCK		0x00000002
  #define FGP_CREAT		0x00000004
  #define FGP_WRITE		0x00000008
  #define FGP_NOFS		0x00000010
  #define FGP_NOWAIT		0x00000020
  
  struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,

  		int fgp_flags, gfp_t cache_gfp_mask);

  
  /**
   * find_get_page - find and get a page reference
   * @mapping: the address_space to search
   * @offset: the page index
   *
   * Looks up the page cache slot at @mapping & @offset.  If there is a
   * page cache page, it is returned with an increased refcount.
   *
   * Otherwise, %NULL is returned.
   */
  static inline struct page *find_get_page(struct address_space *mapping,
  					pgoff_t offset)
  {

  	return pagecache_get_page(mapping, offset, 0, 0);

  }
  
  static inline struct page *find_get_page_flags(struct address_space *mapping,
  					pgoff_t offset, int fgp_flags)
  {

  	return pagecache_get_page(mapping, offset, fgp_flags, 0);

  }
  
  /**
   * find_lock_page - locate, pin and lock a pagecache page

   * @mapping: the address_space to search
   * @offset: the page index
   *
   * Looks up the page cache slot at @mapping & @offset.  If there is a
   * page cache page, it is returned locked and with an increased
   * refcount.
   *
   * Otherwise, %NULL is returned.
   *
   * find_lock_page() may sleep.
   */
  static inline struct page *find_lock_page(struct address_space *mapping,
  					pgoff_t offset)
  {

  	return pagecache_get_page(mapping, offset, FGP_LOCK, 0);

  }
  
  /**
   * find_or_create_page - locate or add a pagecache page
   * @mapping: the page's address_space
   * @index: the page's index into the mapping
   * @gfp_mask: page allocation mode
   *
   * Looks up the page cache slot at @mapping & @offset.  If there is a
   * page cache page, it is returned locked and with an increased
   * refcount.
   *
   * If the page is not present, a new page is allocated using @gfp_mask
   * and added to the page cache and the VM's LRU list.  The page is
   * returned locked and with an increased refcount.
   *
   * On memory exhaustion, %NULL is returned.
   *
   * find_or_create_page() may sleep, even if @gfp_flags specifies an
   * atomic allocation!
   */
  static inline struct page *find_or_create_page(struct address_space *mapping,
  					pgoff_t offset, gfp_t gfp_mask)
  {
  	return pagecache_get_page(mapping, offset,
  					FGP_LOCK|FGP_ACCESSED|FGP_CREAT,

  					gfp_mask);

  }
  
  /**
   * grab_cache_page_nowait - returns locked page at given index in given cache
   * @mapping: target address_space
   * @index: the page index
   *
   * Same as grab_cache_page(), but do not wait if the page is unavailable.
   * This is intended for speculative data generators, where the data can
   * be regenerated if the page couldn't be grabbed.  This routine should
   * be safe to call while holding the lock for another page.
   *
   * Clear __GFP_FS when allocating the page to avoid recursion into the fs
   * and deadlock against the caller's locked page.
   */
  static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
  				pgoff_t index)
  {
  	return pagecache_get_page(mapping, index,
  			FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,

  			mapping_gfp_mask(mapping));

  }

  struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);

  struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);

  unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
  			  unsigned int nr_entries, struct page **entries,
  			  pgoff_t *indices);

  unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
  			pgoff_t end, unsigned int nr_pages,
  			struct page **pages);
  static inline unsigned find_get_pages(struct address_space *mapping,
  			pgoff_t *start, unsigned int nr_pages,
  			struct page **pages)
  {
  	return find_get_pages_range(mapping, start, (pgoff_t)-1, nr_pages,
  				    pages);
  }

  unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
  			       unsigned int nr_pages, struct page **pages);

  unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
  			int tag, unsigned int nr_pages, struct page **pages);

  unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
  			int tag, unsigned int nr_entries,
  			struct page **entries, pgoff_t *indices);

  struct page *grab_cache_page_write_begin(struct address_space *mapping,
  			pgoff_t index, unsigned flags);

  /*
   * Returns locked page at given index in given cache, creating it if needed.
   */

  static inline struct page *grab_cache_page(struct address_space *mapping,
  								pgoff_t index)

  {
  	return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
  }

  extern struct page * read_cache_page(struct address_space *mapping,

  				pgoff_t index, filler_t *filler, void *data);

  extern struct page * read_cache_page_gfp(struct address_space *mapping,
  				pgoff_t index, gfp_t gfp_mask);

  extern int read_cache_pages(struct address_space *mapping,
  		struct list_head *pages, filler_t *filler, void *data);

  static inline struct page *read_mapping_page(struct address_space *mapping,

  				pgoff_t index, void *data)

  {
  	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  	return read_cache_page(mapping, index, filler, data);
  }

  /*

   * Get index of the page with in radix-tree
   * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)

   */

  static inline pgoff_t page_to_index(struct page *page)

  {

  	pgoff_t pgoff;

  	if (likely(!PageTransTail(page)))

  		return page->index;

  
  	/*
  	 *  We don't initialize ->index for tail pages: calculate based on
  	 *  head page
  	 */

  	pgoff = compound_head(page)->index;

  	pgoff += page - compound_head(page);
  	return pgoff;

  }
  
  /*

   * Get the offset in PAGE_SIZE.
   * (TODO: hugepage should have ->index in PAGE_SIZE)
   */
  static inline pgoff_t page_to_pgoff(struct page *page)
  {
  	if (unlikely(PageHeadHuge(page)))
  		return page->index << compound_order(page);
  
  	return page_to_index(page);
  }
  
  /*

   * Return byte-offset into filesystem object for page.
   */
  static inline loff_t page_offset(struct page *page)
  {

  	return ((loff_t)page->index) << PAGE_SHIFT;

  }

  static inline loff_t page_file_offset(struct page *page)
  {

  	return ((loff_t)page_index(page)) << PAGE_SHIFT;

  }

  extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
  				     unsigned long address);

  static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
  					unsigned long address)
  {

  	pgoff_t pgoff;
  	if (unlikely(is_vm_hugetlb_page(vma)))
  		return linear_hugepage_index(vma, address);
  	pgoff = (address - vma->vm_start) >> PAGE_SHIFT;

  	pgoff += vma->vm_pgoff;

  	return pgoff;

  }

  extern void __lock_page(struct page *page);
  extern int __lock_page_killable(struct page *page);

  extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
  				unsigned int flags);

  extern void unlock_page(struct page *page);

  static inline int trylock_page(struct page *page)
  {

  	page = compound_head(page);

  	return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));

  }

  /*
   * lock_page may only be called if we have the page's inode pinned.
   */

  static inline void lock_page(struct page *page)
  {
  	might_sleep();

  	if (!trylock_page(page))

  		__lock_page(page);
  }

  
  /*

   * lock_page_killable is like lock_page but can be interrupted by fatal
   * signals.  It returns 0 if it locked the page and -EINTR if it was
   * killed while waiting.
   */
  static inline int lock_page_killable(struct page *page)
  {
  	might_sleep();

  	if (!trylock_page(page))

  		return __lock_page_killable(page);
  	return 0;
  }
  
  /*

   * lock_page_or_retry - Lock the page, unless this would block and the
   * caller indicated that it can handle a retry.

   *
   * 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, etc.,
   * and should not be used directly.

   */

  extern void wait_on_page_bit(struct page *page, int bit_nr);

  extern int wait_on_page_bit_killable(struct page *page, int bit_nr);

  /* 
   * 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(compound_head(page), PG_locked);

  }

  static inline int wait_on_page_locked_killable(struct page *page)
  {
  	if (!PageLocked(page))
  		return 0;
  	return wait_on_page_bit_killable(compound_head(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, bool is_write, int err);

  /*

   * Add an arbitrary waiter to a page's wait queue
   */

  extern void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter);

  
  /*

   * Fault everything in given userspace address range in.

   */
  static inline int fault_in_pages_writeable(char __user *uaddr, int size)
  {

  	char __user *end = uaddr + size - 1;

  
  	if (unlikely(size == 0))

  		return 0;

  	if (unlikely(uaddr > end))
  		return -EFAULT;

  	/*
  	 * Writing zeroes into userspace here is OK, because we know that if
  	 * the zero gets there, we'll be overwriting it.
  	 */

  	do {
  		if (unlikely(__put_user(0, uaddr) != 0))
  			return -EFAULT;

  		uaddr += PAGE_SIZE;

  	} while (uaddr <= end);

  
  	/* Check whether the range spilled into the next page. */
  	if (((unsigned long)uaddr & PAGE_MASK) ==
  			((unsigned long)end & PAGE_MASK))

  		return __put_user(0, end);

  	return 0;

  }

  static inline int fault_in_pages_readable(const char __user *uaddr, int size)

  {
  	volatile char c;

  	const char __user *end = uaddr + size - 1;
  
  	if (unlikely(size == 0))

  		return 0;

  	if (unlikely(uaddr > end))
  		return -EFAULT;
  
  	do {
  		if (unlikely(__get_user(c, uaddr) != 0))
  			return -EFAULT;

  		uaddr += PAGE_SIZE;

  	} while (uaddr <= end);

  
  	/* Check whether the range spilled into the next page. */
  	if (((unsigned long)uaddr & PAGE_MASK) ==
  			((unsigned long)end & PAGE_MASK)) {

  		return __get_user(c, end);

  	}

  	(void)c;

  	return 0;

  }

  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 __SetPageLocked() 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;

  	__SetPageLocked(page);

  	error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
  	if (unlikely(error))

  		__ClearPageLocked(page);

  	return error;
  }

  static inline unsigned long dir_pages(struct inode *inode)
  {

  	return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
  			       PAGE_SHIFT;

  }

  #endif /* _LINUX_PAGEMAP_H */