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 /* 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>
 
 struct folio_batch;
 
 unsigned long invalidate_mapping_pages(struct address_space *mapping,
                     pgoff_t start, pgoff_t end);
 
 static inline void invalidate_remote_inode(struct inode *inode)
 {
     if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
         S_ISLNK(inode->i_mode))
         invalidate_mapping_pages(inode->i_mapping, 0, -1);
 }
 int invalidate_inode_pages2(struct address_space *mapping);
 int invalidate_inode_pages2_range(struct address_space *mapping,
         pgoff_t start, pgoff_t end);
 int write_inode_now(struct inode *, int sync);
 int filemap_fdatawrite(struct address_space *);
 int filemap_flush(struct address_space *);
 int filemap_fdatawait_keep_errors(struct address_space *mapping);
 int filemap_fdatawait_range(struct address_space *, loff_t lstart, loff_t lend);
 int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
         loff_t start_byte, loff_t end_byte);
 
 static inline int filemap_fdatawait(struct address_space *mapping)
 {
     return filemap_fdatawait_range(mapping, 0, LLONG_MAX);
 }
 
 bool filemap_range_has_page(struct address_space *, loff_t lstart, loff_t lend);
 int filemap_write_and_wait_range(struct address_space *mapping,
         loff_t lstart, loff_t lend);
 int __filemap_fdatawrite_range(struct address_space *mapping,
         loff_t start, loff_t end, int sync_mode);
 int filemap_fdatawrite_range(struct address_space *mapping,
         loff_t start, loff_t end);
 int filemap_check_errors(struct address_space *mapping);
 void __filemap_set_wb_err(struct address_space *mapping, int err);
 int filemap_fdatawrite_wbc(struct address_space *mapping,
                struct writeback_control *wbc);
 
 static inline int filemap_write_and_wait(struct address_space *mapping)
 {
     return filemap_write_and_wait_range(mapping, 0, LLONG_MAX);
 }
 
 /**
  * filemap_set_wb_err - set a writeback error on an address_space
  * @mapping: mapping in which to set writeback error
  * @err: error to be set in 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
  * filemap_set_wb_err to record the error in the mapping so that it will be
  * automatically reported whenever fsync is called on the file.
  */
 static inline void filemap_set_wb_err(struct address_space *mapping, int err)
 {
     /* Fastpath for common case of no error */
     if (unlikely(err))
         __filemap_set_wb_err(mapping, err);
 }
 
 /**
  * filemap_check_wb_err - has an error occurred since the mark was sampled?
  * @mapping: mapping to check for writeback errors
  * @since: previously-sampled errseq_t
  *
  * Grab the errseq_t value from the mapping, and see if it has changed "since"
  * the given value was sampled.
  *
  * If it has then report the latest error set, otherwise return 0.
  */
 static inline int filemap_check_wb_err(struct address_space *mapping,
                     errseq_t since)
 {
     return errseq_check(&mapping->wb_err, since);
 }
 
 /**
  * filemap_sample_wb_err - sample the current errseq_t to test for later errors
  * @mapping: mapping to be sampled
  *
  * Writeback errors are always reported relative to a particular sample point
  * in the past. This function provides those sample points.
  */
 static inline errseq_t filemap_sample_wb_err(struct address_space *mapping)
 {
     return errseq_sample(&mapping->wb_err);
 }
 
 /**
  * file_sample_sb_err - sample the current errseq_t to test for later errors
  * @file: file pointer to be sampled
  *
  * Grab the most current superblock-level errseq_t value for the given
  * struct file.
  */
 static inline errseq_t file_sample_sb_err(struct file *file)
 {
     return errseq_sample(&file->f_path.dentry->d_sb->s_wb_err);
 }
 
 /*
  * Flush file data before changing attributes.  Caller must hold any locks
  * required to prevent further writes to this file until we're done setting
  * flags.
  */
 static inline int inode_drain_writes(struct inode *inode)
 {
     inode_dio_wait(inode);
     return filemap_write_and_wait(inode->i_mapping);
 }
 
 static inline bool mapping_empty(struct address_space *mapping)
 {
     return xa_empty(&mapping->i_pages);
 }
 
 /*
  * mapping_shrinkable - test if page cache state allows inode reclaim
  * @mapping: the page cache mapping
  *
  * This checks the mapping's cache state for the pupose of inode
  * reclaim and LRU management.
  *
  * The caller is expected to hold the i_lock, but is not required to
  * hold the i_pages lock, which usually protects cache state. That's
  * because the i_lock and the list_lru lock that protect the inode and
  * its LRU state don't nest inside the irq-safe i_pages lock.
  *
  * Cache deletions are performed under the i_lock, which ensures that
  * when an inode goes empty, it will reliably get queued on the LRU.
  *
  * Cache additions do not acquire the i_lock and may race with this
  * check, in which case we'll report the inode as shrinkable when it
  * has cache pages. This is okay: the shrinker also checks the
  * refcount and the referenced bit, which will be elevated or set in
  * the process of adding new cache pages to an inode.
  */
 static inline bool mapping_shrinkable(struct address_space *mapping)
 {
     void *head;
 
     /*
      * On highmem systems, there could be lowmem pressure from the
      * inodes before there is highmem pressure from the page
      * cache. Make inodes shrinkable regardless of cache state.
      */
     if (IS_ENABLED(CONFIG_HIGHMEM))
         return true;
 
     /* Cache completely empty? Shrink away. */
     head = rcu_access_pointer(mapping->i_pages.xa_head);
     if (!head)
         return true;
 
     /*
      * The xarray stores single offset-0 entries directly in the
      * head pointer, which allows non-resident page cache entries
      * to escape the shadow shrinker's list of xarray nodes. The
      * inode shrinker needs to pick them up under memory pressure.
      */
     if (!xa_is_node(head) && xa_is_value(head))
         return true;
 
     return false;
 }
 
 /*
  * 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,
     AS_LARGE_FOLIO_SUPPORT = 6,
 };
 
 /**
  * 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 superblock */
     if (mapping->host)
         errseq_set(&mapping->host->i_sb->s_wb_err, 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 bool mapping_unevictable(struct address_space *mapping)
 {
     return mapping && test_bit(AS_UNEVICTABLE, &mapping->flags);
 }
 
 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;
 }
 
 /**
  * mapping_set_large_folios() - Indicate the file supports large folios.
  * @mapping: The file.
  *
  * The filesystem should call this function in its inode constructor to
  * indicate that the VFS can use large folios to cache the contents of
  * the file.
  *
  * Context: This should not be called while the inode is active as it
  * is non-atomic.
  */
 static inline void mapping_set_large_folios(struct address_space *mapping)
 {
     __set_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
 }
 
 /*
  * Large folio support currently depends on THP.  These dependencies are
  * being worked on but are not yet fixed.
  */
 static inline bool mapping_large_folio_support(struct address_space *mapping)
 {
     return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
         test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
 }
 
 static inline int filemap_nr_thps(struct address_space *mapping)
 {
 #ifdef CONFIG_READ_ONLY_THP_FOR_FS
     return atomic_read(&mapping->nr_thps);
 #else
     return 0;
 #endif
 }
 
 static inline void filemap_nr_thps_inc(struct address_space *mapping)
 {
 #ifdef CONFIG_READ_ONLY_THP_FOR_FS
     if (!mapping_large_folio_support(mapping))
         atomic_inc(&mapping->nr_thps);
 #else
     WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
 #endif
 }
 
 static inline void filemap_nr_thps_dec(struct address_space *mapping)
 {
 #ifdef CONFIG_READ_ONLY_THP_FOR_FS
     if (!mapping_large_folio_support(mapping))
         atomic_dec(&mapping->nr_thps);
 #else
     WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
 #endif
 }
 
 struct address_space *page_mapping(struct page *);
 struct address_space *folio_mapping(struct folio *);
 struct address_space *swapcache_mapping(struct folio *);
 
 /**
  * folio_file_mapping - Find the mapping this folio belongs to.
  * @folio: The folio.
  *
  * For folios which are in the page cache, return the mapping that this
  * page belongs to.  Folios in the swap cache return the mapping of the
  * swap file or swap device where the data is stored.  This is different
  * from the mapping returned by folio_mapping().  The only reason to
  * use it is if, like NFS, you return 0 from ->activate_swapfile.
  *
  * Do not call this for folios which aren't in the page cache or swap cache.
  */
 static inline struct address_space *folio_file_mapping(struct folio *folio)
 {
     if (unlikely(folio_test_swapcache(folio)))
         return swapcache_mapping(folio);
 
     return folio->mapping;
 }
 
 static inline struct address_space *page_file_mapping(struct page *page)
 {
     return folio_file_mapping(page_folio(page));
 }
 
 /*
  * For file cache pages, return the address_space, otherwise return NULL
  */
 static inline struct address_space *page_mapping_file(struct page *page)
 {
     struct folio *folio = page_folio(page);
 
     if (unlikely(folio_test_swapcache(folio)))
         return NULL;
     return folio_mapping(folio);
 }
 
 /**
  * folio_inode - Get the host inode for this folio.
  * @folio: The folio.
  *
  * For folios which are in the page cache, return the inode that this folio
  * belongs to.
  *
  * Do not call this for folios which aren't in the page cache.
  */
 static inline struct inode *folio_inode(struct folio *folio)
 {
     return folio->mapping->host;
 }
 
 /**
  * folio_attach_private - Attach private data to a folio.
  * @folio: Folio to attach data to.
  * @data: Data to attach to folio.
  *
  * Attaching private data to a folio increments the page's reference count.
  * The data must be detached before the folio will be freed.
  */
 static inline void folio_attach_private(struct folio *folio, void *data)
 {
     folio_get(folio);
     folio->private = data;
     folio_set_private(folio);
 }
 
 /**
  * folio_change_private - Change private data on a folio.
  * @folio: Folio to change the data on.
  * @data: Data to set on the folio.
  *
  * Change the private data attached to a folio and return the old
  * data.  The page must previously have had data attached and the data
  * must be detached before the folio will be freed.
  *
  * Return: Data that was previously attached to the folio.
  */
 static inline void *folio_change_private(struct folio *folio, void *data)
 {
     void *old = folio_get_private(folio);
 
     folio->private = data;
     return old;
 }
 
 /**
  * folio_detach_private - Detach private data from a folio.
  * @folio: Folio to detach data from.
  *
  * Removes the data that was previously attached to the folio and decrements
  * the refcount on the page.
  *
  * Return: Data that was attached to the folio.
  */
 static inline void *folio_detach_private(struct folio *folio)
 {
     void *data = folio_get_private(folio);
 
     if (!folio_test_private(folio))
         return NULL;
     folio_clear_private(folio);
     folio->private = NULL;
     folio_put(folio);
 
     return data;
 }
 
 static inline void attach_page_private(struct page *page, void *data)
 {
     folio_attach_private(page_folio(page), data);
 }
 
 static inline void *detach_page_private(struct page *page)
 {
     return folio_detach_private(page_folio(page));
 }
 
 #ifdef CONFIG_NUMA
 struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order);
 #else
 static inline struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
 {
     return folio_alloc(gfp, order);
 }
 #endif
 
 static inline struct page *__page_cache_alloc(gfp_t gfp)
 {
     return &filemap_alloc_folio(gfp, 0)->page;
 }
 
 static inline struct page *page_cache_alloc(struct address_space *x)
 {
     return __page_cache_alloc(mapping_gfp_mask(x));
 }
 
 static inline gfp_t readahead_gfp_mask(struct address_space *x)
 {
     return mapping_gfp_mask(x) | __GFP_NORETRY | __GFP_NOWARN;
 }
 
 typedef int filler_t(struct file *, struct folio *);
 
 pgoff_t page_cache_next_miss(struct address_space *mapping,
                  pgoff_t index, unsigned long max_scan);
 pgoff_t page_cache_prev_miss(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
 #define FGP_FOR_MMAP        0x00000040
 #define FGP_HEAD        0x00000080
 #define FGP_ENTRY       0x00000100
 #define FGP_STABLE      0x00000200
 
 struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
         int fgp_flags, gfp_t gfp);
 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
         int fgp_flags, gfp_t gfp);
 
 /**
  * filemap_get_folio - Find and get a folio.
  * @mapping: The address_space to search.
  * @index: The page index.
  *
  * Looks up the page cache entry at @mapping & @index.  If a folio is
  * present, it is returned with an increased refcount.
  *
  * Otherwise, %NULL is returned.
  */
 static inline struct folio *filemap_get_folio(struct address_space *mapping,
                     pgoff_t index)
 {
     return __filemap_get_folio(mapping, index, 0, 0);
 }
 
 /**
  * filemap_lock_folio - Find and lock a folio.
  * @mapping: The address_space to search.
  * @index: The page index.
  *
  * Looks up the page cache entry at @mapping & @index.  If a folio is
  * present, it is returned locked with an increased refcount.
  *
  * Context: May sleep.
  * Return: A folio or %NULL if there is no folio in the cache for this
  * index.  Will not return a shadow, swap or DAX entry.
  */
 static inline struct folio *filemap_lock_folio(struct address_space *mapping,
                     pgoff_t index)
 {
     return __filemap_get_folio(mapping, index, FGP_LOCK, 0);
 }
 
 /**
  * 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
  * @index: the page index
  *
  * Looks up the page cache entry at @mapping & @index.  If there is a
  * page cache page, it is returned locked and with an increased
  * refcount.
  *
  * Context: May sleep.
  * Return: A struct page or %NULL if there is no page in the cache for this
  * index.
  */
 static inline struct page *find_lock_page(struct address_space *mapping,
                     pgoff_t index)
 {
     return pagecache_get_page(mapping, index, 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 index, gfp_t gfp_mask)
 {
     return pagecache_get_page(mapping, index,
                     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));
 }
 
 #define swapcache_index(folio)  __page_file_index(&(folio)->page)
 
 /**
  * folio_index - File index of a folio.
  * @folio: The folio.
  *
  * For a folio which is either in the page cache or the swap cache,
  * return its index within the address_space it belongs to.  If you know
  * the page is definitely in the page cache, you can look at the folio's
  * index directly.
  *
  * Return: The index (offset in units of pages) of a folio in its file.
  */
 static inline pgoff_t folio_index(struct folio *folio)
 {
         if (unlikely(folio_test_swapcache(folio)))
                 return swapcache_index(folio);
         return folio->index;
 }
 
 /**
  * folio_next_index - Get the index of the next folio.
  * @folio: The current folio.
  *
  * Return: The index of the folio which follows this folio in the file.
  */
 static inline pgoff_t folio_next_index(struct folio *folio)
 {
     return folio->index + folio_nr_pages(folio);
 }
 
 /**
  * folio_file_page - The page for a particular index.
  * @folio: The folio which contains this index.
  * @index: The index we want to look up.
  *
  * Sometimes after looking up a folio in the page cache, we need to
  * obtain the specific page for an index (eg a page fault).
  *
  * Return: The page containing the file data for this index.
  */
 static inline struct page *folio_file_page(struct folio *folio, pgoff_t index)
 {
     /* HugeTLBfs indexes the page cache in units of hpage_size */
     if (folio_test_hugetlb(folio))
         return &folio->page;
     return folio_page(folio, index & (folio_nr_pages(folio) - 1));
 }
 
 /**
  * folio_contains - Does this folio contain this index?
  * @folio: The folio.
  * @index: The page index within the file.
  *
  * Context: The caller should have the page locked in order to prevent
  * (eg) shmem from moving the page between the page cache and swap cache
  * and changing its index in the middle of the operation.
  * Return: true or false.
  */
 static inline bool folio_contains(struct folio *folio, pgoff_t index)
 {
     /* HugeTLBfs indexes the page cache in units of hpage_size */
     if (folio_test_hugetlb(folio))
         return folio->index == index;
     return index - folio_index(folio) < folio_nr_pages(folio);
 }
 
 /*
  * Given the page we found in the page cache, return the page corresponding
  * to this index in the file
  */
 static inline struct page *find_subpage(struct page *head, pgoff_t index)
 {
     /* HugeTLBfs wants the head page regardless */
     if (PageHuge(head))
         return head;
 
     return head + (index & (thp_nr_pages(head) - 1));
 }
 
 unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
         pgoff_t end, struct folio_batch *fbatch);
 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
                    unsigned int nr_pages, struct page **pages);
 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
             pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
             struct page **pages);
 static inline unsigned find_get_pages_tag(struct address_space *mapping,
             pgoff_t *index, xa_mark_t tag, unsigned int nr_pages,
             struct page **pages)
 {
     return find_get_pages_range_tag(mapping, index, (pgoff_t)-1, tag,
                     nr_pages, pages);
 }
 
 struct page *grab_cache_page_write_begin(struct address_space *mapping,
             pgoff_t index);
 
 /*
  * 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));
 }
 
 struct folio *read_cache_folio(struct address_space *, pgoff_t index,
         filler_t *filler, struct file *file);
 struct page *read_cache_page(struct address_space *, pgoff_t index,
         filler_t *filler, struct file *file);
 extern struct page * read_cache_page_gfp(struct address_space *mapping,
                 pgoff_t index, gfp_t gfp_mask);
 
 static inline struct page *read_mapping_page(struct address_space *mapping,
                 pgoff_t index, struct file *file)
 {
     return read_cache_page(mapping, index, NULL, file);
 }
 
 static inline struct folio *read_mapping_folio(struct address_space *mapping,
                 pgoff_t index, struct file *file)
 {
     return read_cache_folio(mapping, index, NULL, file);
 }
 
 /*
  * Get index of the page within radix-tree (but not for hugetlb pages).
  * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
  */
 static inline pgoff_t page_to_index(struct page *page)
 {
     struct page *head;
 
     if (likely(!PageTransTail(page)))
         return page->index;
 
     head = compound_head(page);
     /*
      *  We don't initialize ->index for tail pages: calculate based on
      *  head page
      */
     return head->index + page - head;
 }
 
 extern pgoff_t hugetlb_basepage_index(struct page *page);
 
 /*
  * Get the offset in PAGE_SIZE (even for hugetlb pages).
  * (TODO: hugetlb pages should have ->index in PAGE_SIZE)
  */
 static inline pgoff_t page_to_pgoff(struct page *page)
 {
     if (unlikely(PageHuge(page)))
         return hugetlb_basepage_index(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;
 }
 
 /**
  * folio_pos - Returns the byte position of this folio in its file.
  * @folio: The folio.
  */
 static inline loff_t folio_pos(struct folio *folio)
 {
     return page_offset(&folio->page);
 }
 
 /**
  * folio_file_pos - Returns the byte position of this folio in its file.
  * @folio: The folio.
  *
  * This differs from folio_pos() for folios which belong to a swap file.
  * NFS is the only filesystem today which needs to use folio_file_pos().
  */
 static inline loff_t folio_file_pos(struct folio *folio)
 {
     return page_file_offset(&folio->page);
 }
 
 /*
  * Get the offset in PAGE_SIZE (even for hugetlb folios).
  * (TODO: hugetlb folios should have ->index in PAGE_SIZE)
  */
 static inline pgoff_t folio_pgoff(struct folio *folio)
 {
     if (unlikely(folio_test_hugetlb(folio)))
         return hugetlb_basepage_index(&folio->page);
     return folio->index;
 }
 
 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;
 }
 
 struct wait_page_key {
     struct folio *folio;
     int bit_nr;
     int page_match;
 };
 
 struct wait_page_queue {
     struct folio *folio;
     int bit_nr;
     wait_queue_entry_t wait;
 };
 
 static inline bool wake_page_match(struct wait_page_queue *wait_page,
                   struct wait_page_key *key)
 {
     if (wait_page->folio != key->folio)
            return false;
     key->page_match = 1;
 
     if (wait_page->bit_nr != key->bit_nr)
         return false;
 
     return true;
 }
 
 void __folio_lock(struct folio *folio);
 int __folio_lock_killable(struct folio *folio);
 bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
                 unsigned int flags);
 void unlock_page(struct page *page);
 void folio_unlock(struct folio *folio);
 
 /**
  * folio_trylock() - Attempt to lock a folio.
  * @folio: The folio to attempt to lock.
  *
  * Sometimes it is undesirable to wait for a folio to be unlocked (eg
  * when the locks are being taken in the wrong order, or if making
  * progress through a batch of folios is more important than processing
  * them in order).  Usually folio_lock() is the correct function to call.
  *
  * Context: Any context.
  * Return: Whether the lock was successfully acquired.
  */
 static inline bool folio_trylock(struct folio *folio)
 {
     return likely(!test_and_set_bit_lock(PG_locked, folio_flags(folio, 0)));
 }
 
 /*
  * Return true if the page was successfully locked
  */
 static inline int trylock_page(struct page *page)
 {
     return folio_trylock(page_folio(page));
 }
 
 /**
  * folio_lock() - Lock this folio.
  * @folio: The folio to lock.
  *
  * The folio lock protects against many things, probably more than it
  * should.  It is primarily held while a folio is being brought uptodate,
  * either from its backing file or from swap.  It is also held while a
  * folio is being truncated from its address_space, so holding the lock
  * is sufficient to keep folio->mapping stable.
  *
  * The folio lock is also held while write() is modifying the page to
  * provide POSIX atomicity guarantees (as long as the write does not
  * cross a page boundary).  Other modifications to the data in the folio
  * do not hold the folio lock and can race with writes, eg DMA and stores
  * to mapped pages.
  *
  * Context: May sleep.  If you need to acquire the locks of two or
  * more folios, they must be in order of ascending index, if they are
  * in the same address_space.  If they are in different address_spaces,
  * acquire the lock of the folio which belongs to the address_space which
  * has the lowest address in memory first.
  */
 static inline void folio_lock(struct folio *folio)
 {
     might_sleep();
     if (!folio_trylock(folio))
         __folio_lock(folio);
 }
 
 /**
  * lock_page() - Lock the folio containing this page.
  * @page: The page to lock.
  *
  * See folio_lock() for a description of what the lock protects.
  * This is a legacy function and new code should probably use folio_lock()
  * instead.
  *
  * Context: May sleep.  Pages in the same folio share a lock, so do not
  * attempt to lock two pages which share a folio.
  */
 static inline void lock_page(struct page *page)
 {
     struct folio *folio;
     might_sleep();
 
     folio = page_folio(page);
     if (!folio_trylock(folio))
         __folio_lock(folio);
 }
 
 /**
  * folio_lock_killable() - Lock this folio, interruptible by a fatal signal.
  * @folio: The folio to lock.
  *
  * Attempts to lock the folio, like folio_lock(), except that the sleep
  * to acquire the lock is interruptible by a fatal signal.
  *
  * Context: May sleep; see folio_lock().
  * Return: 0 if the lock was acquired; -EINTR if a fatal signal was received.
  */
 static inline int folio_lock_killable(struct folio *folio)
 {
     might_sleep();
     if (!folio_trylock(folio))
         return __folio_lock_killable(folio);
     return 0;
 }
 
 /*
  * 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)
 {
     return folio_lock_killable(page_folio(page));
 }
 
 /*
  * 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_lock implications depend on flags; see
  * __folio_lock_or_retry().
  */
 static inline bool lock_page_or_retry(struct page *page, struct mm_struct *mm,
                      unsigned int flags)
 {
     struct folio *folio;
     might_sleep();
 
     folio = page_folio(page);
     return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags);
 }
 
 /*
  * This is exported only for folio_wait_locked/folio_wait_writeback, etc.,
  * and should not be used directly.
  */
 void folio_wait_bit(struct folio *folio, int bit_nr);
 int folio_wait_bit_killable(struct folio *folio, int bit_nr);
 
 /* 
  * Wait for a folio to be unlocked.
  *
  * This must be called with the caller "holding" the folio,
  * ie with increased folio reference count so that the folio won't
  * go away during the wait.
  */
 static inline void folio_wait_locked(struct folio *folio)
 {
     if (folio_test_locked(folio))
         folio_wait_bit(folio, PG_locked);
 }
 
 static inline int folio_wait_locked_killable(struct folio *folio)
 {
     if (!folio_test_locked(folio))
         return 0;
     return folio_wait_bit_killable(folio, PG_locked);
 }
 
 static inline void wait_on_page_locked(struct page *page)
 {
     folio_wait_locked(page_folio(page));
 }
 
 static inline int wait_on_page_locked_killable(struct page *page)
 {
     return folio_wait_locked_killable(page_folio(page));
 }
 
 int folio_put_wait_locked(struct folio *folio, int state);
 void wait_on_page_writeback(struct page *page);
 void folio_wait_writeback(struct folio *folio);
 int folio_wait_writeback_killable(struct folio *folio);
 void end_page_writeback(struct page *page);
 void folio_end_writeback(struct folio *folio);
 void wait_for_stable_page(struct page *page);
 void folio_wait_stable(struct folio *folio);
 void __folio_mark_dirty(struct folio *folio, struct address_space *, int warn);
 static inline void __set_page_dirty(struct page *page,
         struct address_space *mapping, int warn)
 {
     __folio_mark_dirty(page_folio(page), mapping, warn);
 }
 void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb);
 void __folio_cancel_dirty(struct folio *folio);
 static inline void folio_cancel_dirty(struct folio *folio)
 {
     /* Avoid atomic ops, locking, etc. when not actually needed. */
     if (folio_test_dirty(folio))
         __folio_cancel_dirty(folio);
 }
 bool folio_clear_dirty_for_io(struct folio *folio);
 bool clear_page_dirty_for_io(struct page *page);
 void folio_invalidate(struct folio *folio, size_t offset, size_t length);
 int __must_check folio_write_one(struct folio *folio);
 static inline int __must_check write_one_page(struct page *page)
 {
     return folio_write_one(page_folio(page));
 }
 
 int __set_page_dirty_nobuffers(struct page *page);
 bool noop_dirty_folio(struct address_space *mapping, struct folio *folio);
 
 #ifdef CONFIG_MIGRATION
 int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
         struct folio *src, enum migrate_mode mode);
 #else
 #define filemap_migrate_folio NULL
 #endif
 void page_endio(struct page *page, bool is_write, int err);
 
 void folio_end_private_2(struct folio *folio);
 void folio_wait_private_2(struct folio *folio);
 int folio_wait_private_2_killable(struct folio *folio);
 
 /*
  * Add an arbitrary waiter to a page's wait queue
  */
 void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter);
 
 /*
  * Fault in userspace address range.
  */
 size_t fault_in_writeable(char __user *uaddr, size_t size);
 size_t fault_in_subpage_writeable(char __user *uaddr, size_t size);
 size_t fault_in_safe_writeable(const char __user *uaddr, size_t size);
 size_t fault_in_readable(const char __user *uaddr, size_t size);
 
 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
         pgoff_t index, gfp_t gfp);
 int filemap_add_folio(struct address_space *mapping, struct folio *folio,
         pgoff_t index, gfp_t gfp);
 void filemap_remove_folio(struct folio *folio);
 void delete_from_page_cache(struct page *page);
 void __filemap_remove_folio(struct folio *folio, void *shadow);
 void replace_page_cache_page(struct page *old, struct page *new);
 void delete_from_page_cache_batch(struct address_space *mapping,
                   struct folio_batch *fbatch);
 int try_to_release_page(struct page *page, gfp_t gfp);
 bool filemap_release_folio(struct folio *folio, gfp_t gfp);
 loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
         int whence);
 
 /* Must be non-static for BPF error injection */
 int __filemap_add_folio(struct address_space *mapping, struct folio *folio,
         pgoff_t index, gfp_t gfp, void **shadowp);
 
 bool filemap_range_has_writeback(struct address_space *mapping,
                  loff_t start_byte, loff_t end_byte);
 
 /**
  * filemap_range_needs_writeback - check if range potentially needs writeback
  * @mapping:           address space within which to check
  * @start_byte:        offset in bytes where the range starts
  * @end_byte:          offset in bytes where the range ends (inclusive)
  *
  * Find at least one page in the range supplied, usually used to check if
  * direct writing in this range will trigger a writeback. Used by O_DIRECT
  * read/write with IOCB_NOWAIT, to see if the caller needs to do
  * filemap_write_and_wait_range() before proceeding.
  *
  * Return: %true if the caller should do filemap_write_and_wait_range() before
  * doing O_DIRECT to a page in this range, %false otherwise.
  */
 static inline bool filemap_range_needs_writeback(struct address_space *mapping,
                          loff_t start_byte,
                          loff_t end_byte)
 {
     if (!mapping->nrpages)
         return false;
     if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
         !mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
         return false;
     return filemap_range_has_writeback(mapping, start_byte, end_byte);
 }
 
 /**
  * struct readahead_control - Describes a readahead request.
  *
  * A readahead request is for consecutive pages.  Filesystems which
  * implement the ->readahead method should call readahead_page() or
  * readahead_page_batch() in a loop and attempt to start I/O against
  * each page in the request.
  *
  * Most of the fields in this struct are private and should be accessed
  * by the functions below.
  *
  * @file: The file, used primarily by network filesystems for authentication.
  *    May be NULL if invoked internally by the filesystem.
  * @mapping: Readahead this filesystem object.
  * @ra: File readahead state.  May be NULL.
  */
 struct readahead_control {
     struct file *file;
     struct address_space *mapping;
     struct file_ra_state *ra;
 /* private: use the readahead_* accessors instead */
     pgoff_t _index;
     unsigned int _nr_pages;
     unsigned int _batch_count;
 };
 
 #define DEFINE_READAHEAD(ractl, f, r, m, i)             \
     struct readahead_control ractl = {              \
         .file = f,                      \
         .mapping = m,                       \
         .ra = r,                        \
         ._index = i,                        \
     }
 
 #define VM_READAHEAD_PAGES  (SZ_128K / PAGE_SIZE)
 
 void page_cache_ra_unbounded(struct readahead_control *,
         unsigned long nr_to_read, unsigned long lookahead_count);
 void page_cache_sync_ra(struct readahead_control *, unsigned long req_count);
 void page_cache_async_ra(struct readahead_control *, struct folio *,
         unsigned long req_count);
 void readahead_expand(struct readahead_control *ractl,
               loff_t new_start, size_t new_len);
 
 /**
  * page_cache_sync_readahead - generic file readahead
  * @mapping: address_space which holds the pagecache and I/O vectors
  * @ra: file_ra_state which holds the readahead state
  * @file: Used by the filesystem for authentication.
  * @index: Index of first page to be read.
  * @req_count: Total number of pages being read by the caller.
  *
  * page_cache_sync_readahead() should be called when a cache miss happened:
  * it will submit the read.  The readahead logic may decide to piggyback more
  * pages onto the read request if access patterns suggest it will improve
  * performance.
  */
 static inline
 void page_cache_sync_readahead(struct address_space *mapping,
         struct file_ra_state *ra, struct file *file, pgoff_t index,
         unsigned long req_count)
 {
     DEFINE_READAHEAD(ractl, file, ra, mapping, index);
     page_cache_sync_ra(&ractl, req_count);
 }
 
 /**
  * page_cache_async_readahead - file readahead for marked pages
  * @mapping: address_space which holds the pagecache and I/O vectors
  * @ra: file_ra_state which holds the readahead state
  * @file: Used by the filesystem for authentication.
  * @folio: The folio at @index which triggered the readahead call.
  * @index: Index of first page to be read.
  * @req_count: Total number of pages being read by the caller.
  *
  * page_cache_async_readahead() should be called when a page is used which
  * is marked as PageReadahead; this is a marker to suggest that the application
  * has used up enough of the readahead window that we should start pulling in
  * more pages.
  */
 static inline
 void page_cache_async_readahead(struct address_space *mapping,
         struct file_ra_state *ra, struct file *file,
         struct folio *folio, pgoff_t index, unsigned long req_count)
 {
     DEFINE_READAHEAD(ractl, file, ra, mapping, index);
     page_cache_async_ra(&ractl, folio, req_count);
 }
 
 static inline struct folio *__readahead_folio(struct readahead_control *ractl)
 {
     struct folio *folio;
 
     BUG_ON(ractl->_batch_count > ractl->_nr_pages);
     ractl->_nr_pages -= ractl->_batch_count;
     ractl->_index += ractl->_batch_count;
 
     if (!ractl->_nr_pages) {
         ractl->_batch_count = 0;
         return NULL;
     }
 
     folio = xa_load(&ractl->mapping->i_pages, ractl->_index);
     VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
     ractl->_batch_count = folio_nr_pages(folio);
 
     return folio;
 }
 
 /**
  * readahead_page - Get the next page to read.
  * @ractl: The current readahead request.
  *
  * Context: The page is locked and has an elevated refcount.  The caller
  * should decreases the refcount once the page has been submitted for I/O
  * and unlock the page once all I/O to that page has completed.
  * Return: A pointer to the next page, or %NULL if we are done.
  */
 static inline struct page *readahead_page(struct readahead_control *ractl)
 {
     struct folio *folio = __readahead_folio(ractl);
 
     return &folio->page;
 }
 
 /**
  * readahead_folio - Get the next folio to read.
  * @ractl: The current readahead request.
  *
  * Context: The folio is locked.  The caller should unlock the folio once
  * all I/O to that folio has completed.
  * Return: A pointer to the next folio, or %NULL if we are done.
  */
 static inline struct folio *readahead_folio(struct readahead_control *ractl)
 {
     struct folio *folio = __readahead_folio(ractl);
 
     if (folio)
         folio_put(folio);
     return folio;
 }
 
 static inline unsigned int __readahead_batch(struct readahead_control *rac,
         struct page **array, unsigned int array_sz)
 {
     unsigned int i = 0;
     XA_STATE(xas, &rac->mapping->i_pages, 0);
     struct page *page;
 
     BUG_ON(rac->_batch_count > rac->_nr_pages);
     rac->_nr_pages -= rac->_batch_count;
     rac->_index += rac->_batch_count;
     rac->_batch_count = 0;
 
     xas_set(&xas, rac->_index);
     rcu_read_lock();
     xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) {
         if (xas_retry(&xas, page))
             continue;
         VM_BUG_ON_PAGE(!PageLocked(page), page);
         VM_BUG_ON_PAGE(PageTail(page), page);
         array[i++] = page;
         rac->_batch_count += thp_nr_pages(page);
         if (i == array_sz)
             break;
     }
     rcu_read_unlock();
 
     return i;
 }
 
 /**
  * readahead_page_batch - Get a batch of pages to read.
  * @rac: The current readahead request.
  * @array: An array of pointers to struct page.
  *
  * Context: The pages are locked and have an elevated refcount.  The caller
  * should decreases the refcount once the page has been submitted for I/O
  * and unlock the page once all I/O to that page has completed.
  * Return: The number of pages placed in the array.  0 indicates the request
  * is complete.
  */
 #define readahead_page_batch(rac, array)                \
     __readahead_batch(rac, array, ARRAY_SIZE(array))
 
 /**
  * readahead_pos - The byte offset into the file of this readahead request.
  * @rac: The readahead request.
  */
 static inline loff_t readahead_pos(struct readahead_control *rac)
 {
     return (loff_t)rac->_index * PAGE_SIZE;
 }
 
 /**
  * readahead_length - The number of bytes in this readahead request.
  * @rac: The readahead request.
  */
 static inline size_t readahead_length(struct readahead_control *rac)
 {
     return rac->_nr_pages * PAGE_SIZE;
 }
 
 /**
  * readahead_index - The index of the first page in this readahead request.
  * @rac: The readahead request.
  */
 static inline pgoff_t readahead_index(struct readahead_control *rac)
 {
     return rac->_index;
 }
 
 /**
  * readahead_count - The number of pages in this readahead request.
  * @rac: The readahead request.
  */
 static inline unsigned int readahead_count(struct readahead_control *rac)
 {
     return rac->_nr_pages;
 }
 
 /**
  * readahead_batch_length - The number of bytes in the current batch.
  * @rac: The readahead request.
  */
 static inline size_t readahead_batch_length(struct readahead_control *rac)
 {
     return rac->_batch_count * PAGE_SIZE;
 }
 
 static inline unsigned long dir_pages(struct inode *inode)
 {
     return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
                    PAGE_SHIFT;
 }
 
 /**
  * folio_mkwrite_check_truncate - check if folio was truncated
  * @folio: the folio to check
  * @inode: the inode to check the folio against
  *
  * Return: the number of bytes in the folio up to EOF,
  * or -EFAULT if the folio was truncated.
  */
 static inline ssize_t folio_mkwrite_check_truncate(struct folio *folio,
                           struct inode *inode)
 {
     loff_t size = i_size_read(inode);
     pgoff_t index = size >> PAGE_SHIFT;
     size_t offset = offset_in_folio(folio, size);
 
     if (!folio->mapping)
         return -EFAULT;
 
     /* folio is wholly inside EOF */
     if (folio_next_index(folio) - 1 < index)
         return folio_size(folio);
     /* folio is wholly past EOF */
     if (folio->index > index || !offset)
         return -EFAULT;
     /* folio is partially inside EOF */
     return offset;
 }
 
 /**
  * page_mkwrite_check_truncate - check if page was truncated
  * @page: the page to check
  * @inode: the inode to check the page against
  *
  * Returns the number of bytes in the page up to EOF,
  * or -EFAULT if the page was truncated.
  */
 static inline int page_mkwrite_check_truncate(struct page *page,
                           struct inode *inode)
 {
     loff_t size = i_size_read(inode);
     pgoff_t index = size >> PAGE_SHIFT;
     int offset = offset_in_page(size);
 
     if (page->mapping != inode->i_mapping)
         return -EFAULT;
 
     /* page is wholly inside EOF */
     if (page->index < index)
         return PAGE_SIZE;
     /* page is wholly past EOF */
     if (page->index > index || !offset)
         return -EFAULT;
     /* page is partially inside EOF */
     return offset;
 }
 
 /**
  * i_blocks_per_folio - How many blocks fit in this folio.
  * @inode: The inode which contains the blocks.
  * @folio: The folio.
  *
  * If the block size is larger than the size of this folio, return zero.
  *
  * Context: The caller should hold a refcount on the folio to prevent it
  * from being split.
  * Return: The number of filesystem blocks covered by this folio.
  */
 static inline
 unsigned int i_blocks_per_folio(struct inode *inode, struct folio *folio)
 {
     return folio_size(folio) >> inode->i_blkbits;
 }
 
 static inline
 unsigned int i_blocks_per_page(struct inode *inode, struct page *page)
 {
     return i_blocks_per_folio(inode, page_folio(page));
 }
 #endif /* _LINUX_PAGEMAP_H */

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