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 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /* internal.h: mm/ internal definitions
  *
  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */
 #ifndef __MM_INTERNAL_H
 #define __MM_INTERNAL_H
 
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/rmap.h>
 #include <linux/tracepoint-defs.h>
 
 struct folio_batch;
 
 /*
  * The set of flags that only affect watermark checking and reclaim
  * behaviour. This is used by the MM to obey the caller constraints
  * about IO, FS and watermark checking while ignoring placement
  * hints such as HIGHMEM usage.
  */
 #define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\
             __GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NOFAIL|\
             __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\
             __GFP_ATOMIC|__GFP_NOLOCKDEP)
 
 /* The GFP flags allowed during early boot */
 #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS))
 
 /* Control allocation cpuset and node placement constraints */
 #define GFP_CONSTRAINT_MASK (__GFP_HARDWALL|__GFP_THISNODE)
 
 /* Do not use these with a slab allocator */
 #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
 
 /*
  * Different from WARN_ON_ONCE(), no warning will be issued
  * when we specify __GFP_NOWARN.
  */
 #define WARN_ON_ONCE_GFP(cond, gfp) ({              \
     static bool __section(".data.once") __warned;           \
     int __ret_warn_once = !!(cond);                 \
                                     \
     if (unlikely(!(gfp & __GFP_NOWARN) && __ret_warn_once && !__warned)) { \
         __warned = true;                    \
         WARN_ON(1);                     \
     }                               \
     unlikely(__ret_warn_once);                  \
 })
 
 void page_writeback_init(void);
 
 static inline void *folio_raw_mapping(struct folio *folio)
 {
     unsigned long mapping = (unsigned long)folio->mapping;
 
     return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
 }
 
 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
                         int nr_throttled);
 static inline void acct_reclaim_writeback(struct folio *folio)
 {
     pg_data_t *pgdat = folio_pgdat(folio);
     int nr_throttled = atomic_read(&pgdat->nr_writeback_throttled);
 
     if (nr_throttled)
         __acct_reclaim_writeback(pgdat, folio, nr_throttled);
 }
 
 static inline void wake_throttle_isolated(pg_data_t *pgdat)
 {
     wait_queue_head_t *wqh;
 
     wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_ISOLATED];
     if (waitqueue_active(wqh))
         wake_up(wqh);
 }
 
 vm_fault_t do_swap_page(struct vm_fault *vmf);
 void folio_rotate_reclaimable(struct folio *folio);
 bool __folio_end_writeback(struct folio *folio);
 void deactivate_file_folio(struct folio *folio);
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
         unsigned long floor, unsigned long ceiling);
 void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
 
 struct zap_details;
 void unmap_page_range(struct mmu_gather *tlb,
                  struct vm_area_struct *vma,
                  unsigned long addr, unsigned long end,
                  struct zap_details *details);
 
 void page_cache_ra_order(struct readahead_control *, struct file_ra_state *,
         unsigned int order);
 void force_page_cache_ra(struct readahead_control *, unsigned long nr);
 static inline void force_page_cache_readahead(struct address_space *mapping,
         struct file *file, pgoff_t index, unsigned long nr_to_read)
 {
     DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, index);
     force_page_cache_ra(&ractl, nr_to_read);
 }
 
 unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
         pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
         pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
 void filemap_free_folio(struct address_space *mapping, struct folio *folio);
 int truncate_inode_folio(struct address_space *mapping, struct folio *folio);
 bool truncate_inode_partial_folio(struct folio *folio, loff_t start,
         loff_t end);
 long invalidate_inode_page(struct page *page);
 unsigned long invalidate_mapping_pagevec(struct address_space *mapping,
         pgoff_t start, pgoff_t end, unsigned long *nr_pagevec);
 
 /**
  * folio_evictable - Test whether a folio is evictable.
  * @folio: The folio to test.
  *
  * Test whether @folio is evictable -- i.e., should be placed on
  * active/inactive lists vs unevictable list.
  *
  * Reasons folio might not be evictable:
  * 1. folio's mapping marked unevictable
  * 2. One of the pages in the folio is part of an mlocked VMA
  */
 static inline bool folio_evictable(struct folio *folio)
 {
     bool ret;
 
     /* Prevent address_space of inode and swap cache from being freed */
     rcu_read_lock();
     ret = !mapping_unevictable(folio_mapping(folio)) &&
             !folio_test_mlocked(folio);
     rcu_read_unlock();
     return ret;
 }
 
 static inline bool page_evictable(struct page *page)
 {
     bool ret;
 
     /* Prevent address_space of inode and swap cache from being freed */
     rcu_read_lock();
     ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
     rcu_read_unlock();
     return ret;
 }
 
 /*
  * Turn a non-refcounted page (->_refcount == 0) into refcounted with
  * a count of one.
  */
 static inline void set_page_refcounted(struct page *page)
 {
     VM_BUG_ON_PAGE(PageTail(page), page);
     VM_BUG_ON_PAGE(page_ref_count(page), page);
     set_page_count(page, 1);
 }
 
 extern unsigned long highest_memmap_pfn;
 
 /*
  * Maximum number of reclaim retries without progress before the OOM
  * killer is consider the only way forward.
  */
 #define MAX_RECLAIM_RETRIES 16
 
 /*
  * in mm/early_ioremap.c
  */
 pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
                     unsigned long size, pgprot_t prot);
 
 /*
  * in mm/vmscan.c:
  */
 int isolate_lru_page(struct page *page);
 int folio_isolate_lru(struct folio *folio);
 void putback_lru_page(struct page *page);
 void folio_putback_lru(struct folio *folio);
 extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
 
 /*
  * in mm/rmap.c:
  */
 extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
 
 /*
  * in mm/page_alloc.c
  */
 
 /*
  * Structure for holding the mostly immutable allocation parameters passed
  * between functions involved in allocations, including the alloc_pages*
  * family of functions.
  *
  * nodemask, migratetype and highest_zoneidx are initialized only once in
  * __alloc_pages() and then never change.
  *
  * zonelist, preferred_zone and highest_zoneidx are set first in
  * __alloc_pages() for the fast path, and might be later changed
  * in __alloc_pages_slowpath(). All other functions pass the whole structure
  * by a const pointer.
  */
 struct alloc_context {
     struct zonelist *zonelist;
     nodemask_t *nodemask;
     struct zoneref *preferred_zoneref;
     int migratetype;
 
     /*
      * highest_zoneidx represents highest usable zone index of
      * the allocation request. Due to the nature of the zone,
      * memory on lower zone than the highest_zoneidx will be
      * protected by lowmem_reserve[highest_zoneidx].
      *
      * highest_zoneidx is also used by reclaim/compaction to limit
      * the target zone since higher zone than this index cannot be
      * usable for this allocation request.
      */
     enum zone_type highest_zoneidx;
     bool spread_dirty_pages;
 };
 
 /*
  * This function returns the order of a free page in the buddy system. In
  * general, page_zone(page)->lock must be held by the caller to prevent the
  * page from being allocated in parallel and returning garbage as the order.
  * If a caller does not hold page_zone(page)->lock, it must guarantee that the
  * page cannot be allocated or merged in parallel. Alternatively, it must
  * handle invalid values gracefully, and use buddy_order_unsafe() below.
  */
 static inline unsigned int buddy_order(struct page *page)
 {
     /* PageBuddy() must be checked by the caller */
     return page_private(page);
 }
 
 /*
  * Like buddy_order(), but for callers who cannot afford to hold the zone lock.
  * PageBuddy() should be checked first by the caller to minimize race window,
  * and invalid values must be handled gracefully.
  *
  * READ_ONCE is used so that if the caller assigns the result into a local
  * variable and e.g. tests it for valid range before using, the compiler cannot
  * decide to remove the variable and inline the page_private(page) multiple
  * times, potentially observing different values in the tests and the actual
  * use of the result.
  */
 #define buddy_order_unsafe(page)    READ_ONCE(page_private(page))
 
 /*
  * This function checks whether a page is free && is the buddy
  * we can coalesce a page and its buddy if
  * (a) the buddy is not in a hole (check before calling!) &&
  * (b) the buddy is in the buddy system &&
  * (c) a page and its buddy have the same order &&
  * (d) a page and its buddy are in the same zone.
  *
  * For recording whether a page is in the buddy system, we set PageBuddy.
  * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
  *
  * For recording page's order, we use page_private(page).
  */
 static inline bool page_is_buddy(struct page *page, struct page *buddy,
                  unsigned int order)
 {
     if (!page_is_guard(buddy) && !PageBuddy(buddy))
         return false;
 
     if (buddy_order(buddy) != order)
         return false;
 
     /*
      * zone check is done late to avoid uselessly calculating
      * zone/node ids for pages that could never merge.
      */
     if (page_zone_id(page) != page_zone_id(buddy))
         return false;
 
     VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
 
     return true;
 }
 
 /*
  * Locate the struct page for both the matching buddy in our
  * pair (buddy1) and the combined O(n+1) page they form (page).
  *
  * 1) Any buddy B1 will have an order O twin B2 which satisfies
  * the following equation:
  *     B2 = B1 ^ (1 << O)
  * For example, if the starting buddy (buddy2) is #8 its order
  * 1 buddy is #10:
  *     B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10
  *
  * 2) Any buddy B will have an order O+1 parent P which
  * satisfies the following equation:
  *     P = B & ~(1 << O)
  *
  * Assumption: *_mem_map is contiguous at least up to MAX_ORDER
  */
 static inline unsigned long
 __find_buddy_pfn(unsigned long page_pfn, unsigned int order)
 {
     return page_pfn ^ (1 << order);
 }
 
 /*
  * Find the buddy of @page and validate it.
  * @page: The input page
  * @pfn: The pfn of the page, it saves a call to page_to_pfn() when the
  *       function is used in the performance-critical __free_one_page().
  * @order: The order of the page
  * @buddy_pfn: The output pointer to the buddy pfn, it also saves a call to
  *             page_to_pfn().
  *
  * The found buddy can be a non PageBuddy, out of @page's zone, or its order is
  * not the same as @page. The validation is necessary before use it.
  *
  * Return: the found buddy page or NULL if not found.
  */
 static inline struct page *find_buddy_page_pfn(struct page *page,
             unsigned long pfn, unsigned int order, unsigned long *buddy_pfn)
 {
     unsigned long __buddy_pfn = __find_buddy_pfn(pfn, order);
     struct page *buddy;
 
     buddy = page + (__buddy_pfn - pfn);
     if (buddy_pfn)
         *buddy_pfn = __buddy_pfn;
 
     if (page_is_buddy(page, buddy, order))
         return buddy;
     return NULL;
 }
 
 extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
                 unsigned long end_pfn, struct zone *zone);
 
 static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
                 unsigned long end_pfn, struct zone *zone)
 {
     if (zone->contiguous)
         return pfn_to_page(start_pfn);
 
     return __pageblock_pfn_to_page(start_pfn, end_pfn, zone);
 }
 
 extern int __isolate_free_page(struct page *page, unsigned int order);
 extern void __putback_isolated_page(struct page *page, unsigned int order,
                     int mt);
 extern void memblock_free_pages(struct page *page, unsigned long pfn,
                     unsigned int order);
 extern void __free_pages_core(struct page *page, unsigned int order);
 extern void prep_compound_page(struct page *page, unsigned int order);
 extern void post_alloc_hook(struct page *page, unsigned int order,
                     gfp_t gfp_flags);
 extern int user_min_free_kbytes;
 
 extern void free_unref_page(struct page *page, unsigned int order);
 extern void free_unref_page_list(struct list_head *list);
 
 extern void zone_pcp_update(struct zone *zone, int cpu_online);
 extern void zone_pcp_reset(struct zone *zone);
 extern void zone_pcp_disable(struct zone *zone);
 extern void zone_pcp_enable(struct zone *zone);
 
 extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
               phys_addr_t min_addr,
               int nid, bool exact_nid);
 
 int split_free_page(struct page *free_page,
             unsigned int order, unsigned long split_pfn_offset);
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
 
 /*
  * in mm/compaction.c
  */
 /*
  * compact_control is used to track pages being migrated and the free pages
  * they are being migrated to during memory compaction. The free_pfn starts
  * at the end of a zone and migrate_pfn begins at the start. Movable pages
  * are moved to the end of a zone during a compaction run and the run
  * completes when free_pfn <= migrate_pfn
  */
 struct compact_control {
     struct list_head freepages; /* List of free pages to migrate to */
     struct list_head migratepages;  /* List of pages being migrated */
     unsigned int nr_freepages;  /* Number of isolated free pages */
     unsigned int nr_migratepages;   /* Number of pages to migrate */
     unsigned long free_pfn;     /* isolate_freepages search base */
     /*
      * Acts as an in/out parameter to page isolation for migration.
      * isolate_migratepages uses it as a search base.
      * isolate_migratepages_block will update the value to the next pfn
      * after the last isolated one.
      */
     unsigned long migrate_pfn;
     unsigned long fast_start_pfn;   /* a pfn to start linear scan from */
     struct zone *zone;
     unsigned long total_migrate_scanned;
     unsigned long total_free_scanned;
     unsigned short fast_search_fail;/* failures to use free list searches */
     short search_order;     /* order to start a fast search at */
     const gfp_t gfp_mask;       /* gfp mask of a direct compactor */
     int order;          /* order a direct compactor needs */
     int migratetype;        /* migratetype of direct compactor */
     const unsigned int alloc_flags; /* alloc flags of a direct compactor */
     const int highest_zoneidx;  /* zone index of a direct compactor */
     enum migrate_mode mode;     /* Async or sync migration mode */
     bool ignore_skip_hint;      /* Scan blocks even if marked skip */
     bool no_set_skip_hint;      /* Don't mark blocks for skipping */
     bool ignore_block_suitable; /* Scan blocks considered unsuitable */
     bool direct_compaction;     /* False from kcompactd or /proc/... */
     bool proactive_compaction;  /* kcompactd proactive compaction */
     bool whole_zone;        /* Whole zone should/has been scanned */
     bool contended;         /* Signal lock contention */
     bool rescan;            /* Rescanning the same pageblock */
     bool alloc_contig;      /* alloc_contig_range allocation */
 };
 
 /*
  * Used in direct compaction when a page should be taken from the freelists
  * immediately when one is created during the free path.
  */
 struct capture_control {
     struct compact_control *cc;
     struct page *page;
 };
 
 unsigned long
 isolate_freepages_range(struct compact_control *cc,
             unsigned long start_pfn, unsigned long end_pfn);
 int
 isolate_migratepages_range(struct compact_control *cc,
                unsigned long low_pfn, unsigned long end_pfn);
 
 int __alloc_contig_migrate_range(struct compact_control *cc,
                     unsigned long start, unsigned long end);
 #endif
 int find_suitable_fallback(struct free_area *area, unsigned int order,
             int migratetype, bool only_stealable, bool *can_steal);
 
 /*
  * These three helpers classifies VMAs for virtual memory accounting.
  */
 
 /*
  * Executable code area - executable, not writable, not stack
  */
 static inline bool is_exec_mapping(vm_flags_t flags)
 {
     return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC;
 }
 
 /*
  * Stack area - automatically grows in one direction
  *
  * VM_GROWSUP / VM_GROWSDOWN VMAs are always private anonymous:
  * do_mmap() forbids all other combinations.
  */
 static inline bool is_stack_mapping(vm_flags_t flags)
 {
     return (flags & VM_STACK) == VM_STACK;
 }
 
 /*
  * Data area - private, writable, not stack
  */
 static inline bool is_data_mapping(vm_flags_t flags)
 {
     return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
 }
 
 /* mm/util.c */
 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
         struct vm_area_struct *prev);
 void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma);
 struct anon_vma *folio_anon_vma(struct folio *folio);
 
 #ifdef CONFIG_MMU
 void unmap_mapping_folio(struct folio *folio);
 extern long populate_vma_page_range(struct vm_area_struct *vma,
         unsigned long start, unsigned long end, int *locked);
 extern long faultin_vma_page_range(struct vm_area_struct *vma,
                    unsigned long start, unsigned long end,
                    bool write, int *locked);
 extern int mlock_future_check(struct mm_struct *mm, unsigned long flags,
                   unsigned long len);
 /*
  * mlock_vma_page() and munlock_vma_page():
  * should be called with vma's mmap_lock held for read or write,
  * under page table lock for the pte/pmd being added or removed.
  *
  * mlock is usually called at the end of page_add_*_rmap(),
  * munlock at the end of page_remove_rmap(); but new anon
  * pages are managed by lru_cache_add_inactive_or_unevictable()
  * calling mlock_new_page().
  *
  * @compound is used to include pmd mappings of THPs, but filter out
  * pte mappings of THPs, which cannot be consistently counted: a pte
  * mapping of the THP head cannot be distinguished by the page alone.
  */
 void mlock_folio(struct folio *folio);
 static inline void mlock_vma_folio(struct folio *folio,
             struct vm_area_struct *vma, bool compound)
 {
     /*
      * The VM_SPECIAL check here serves two purposes.
      * 1) VM_IO check prevents migration from double-counting during mlock.
      * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED
      *    is never left set on a VM_SPECIAL vma, there is an interval while
      *    file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may
      *    still be set while VM_SPECIAL bits are added: so ignore it then.
      */
     if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED) &&
         (compound || !folio_test_large(folio)))
         mlock_folio(folio);
 }
 
 static inline void mlock_vma_page(struct page *page,
             struct vm_area_struct *vma, bool compound)
 {
     mlock_vma_folio(page_folio(page), vma, compound);
 }
 
 void munlock_page(struct page *page);
 static inline void munlock_vma_page(struct page *page,
             struct vm_area_struct *vma, bool compound)
 {
     if (unlikely(vma->vm_flags & VM_LOCKED) &&
         (compound || !PageTransCompound(page)))
         munlock_page(page);
 }
 void mlock_new_page(struct page *page);
 bool need_mlock_page_drain(int cpu);
 void mlock_page_drain_local(void);
 void mlock_page_drain_remote(int cpu);
 
 extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
 
 /*
  * Return the start of user virtual address at the specific offset within
  * a vma.
  */
 static inline unsigned long
 vma_pgoff_address(pgoff_t pgoff, unsigned long nr_pages,
           struct vm_area_struct *vma)
 {
     unsigned long address;
 
     if (pgoff >= vma->vm_pgoff) {
         address = vma->vm_start +
             ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
         /* Check for address beyond vma (or wrapped through 0?) */
         if (address < vma->vm_start || address >= vma->vm_end)
             address = -EFAULT;
     } else if (pgoff + nr_pages - 1 >= vma->vm_pgoff) {
         /* Test above avoids possibility of wrap to 0 on 32-bit */
         address = vma->vm_start;
     } else {
         address = -EFAULT;
     }
     return address;
 }
 
 /*
  * Return the start of user virtual address of a page within a vma.
  * Returns -EFAULT if all of the page is outside the range of vma.
  * If page is a compound head, the entire compound page is considered.
  */
 static inline unsigned long
 vma_address(struct page *page, struct vm_area_struct *vma)
 {
     VM_BUG_ON_PAGE(PageKsm(page), page);    /* KSM page->index unusable */
     return vma_pgoff_address(page_to_pgoff(page), compound_nr(page), vma);
 }
 
 /*
  * Then at what user virtual address will none of the range be found in vma?
  * Assumes that vma_address() already returned a good starting address.
  */
 static inline unsigned long vma_address_end(struct page_vma_mapped_walk *pvmw)
 {
     struct vm_area_struct *vma = pvmw->vma;
     pgoff_t pgoff;
     unsigned long address;
 
     /* Common case, plus ->pgoff is invalid for KSM */
     if (pvmw->nr_pages == 1)
         return pvmw->address + PAGE_SIZE;
 
     pgoff = pvmw->pgoff + pvmw->nr_pages;
     address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
     /* Check for address beyond vma (or wrapped through 0?) */
     if (address < vma->vm_start || address > vma->vm_end)
         address = vma->vm_end;
     return address;
 }
 
 static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
                             struct file *fpin)
 {
     int flags = vmf->flags;
 
     if (fpin)
         return fpin;
 
     /*
      * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
      * anything, so we only pin the file and drop the mmap_lock if only
      * FAULT_FLAG_ALLOW_RETRY is set, while this is the first attempt.
      */
     if (fault_flag_allow_retry_first(flags) &&
         !(flags & FAULT_FLAG_RETRY_NOWAIT)) {
         fpin = get_file(vmf->vma->vm_file);
         mmap_read_unlock(vmf->vma->vm_mm);
     }
     return fpin;
 }
 #else /* !CONFIG_MMU */
 static inline void unmap_mapping_folio(struct folio *folio) { }
 static inline void mlock_vma_page(struct page *page,
             struct vm_area_struct *vma, bool compound) { }
 static inline void munlock_vma_page(struct page *page,
             struct vm_area_struct *vma, bool compound) { }
 static inline void mlock_new_page(struct page *page) { }
 static inline bool need_mlock_page_drain(int cpu) { return false; }
 static inline void mlock_page_drain_local(void) { }
 static inline void mlock_page_drain_remote(int cpu) { }
 static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
 {
 }
 #endif /* !CONFIG_MMU */
 
 /*
  * Return the mem_map entry representing the 'offset' subpage within
  * the maximally aligned gigantic page 'base'.  Handle any discontiguity
  * in the mem_map at MAX_ORDER_NR_PAGES boundaries.
  */
 static inline struct page *mem_map_offset(struct page *base, int offset)
 {
     if (unlikely(offset >= MAX_ORDER_NR_PAGES))
         return nth_page(base, offset);
     return base + offset;
 }
 
 /*
  * Iterator over all subpages within the maximally aligned gigantic
  * page 'base'.  Handle any discontiguity in the mem_map.
  */
 static inline struct page *mem_map_next(struct page *iter,
                         struct page *base, int offset)
 {
     if (unlikely((offset & (MAX_ORDER_NR_PAGES - 1)) == 0)) {
         unsigned long pfn = page_to_pfn(base) + offset;
         if (!pfn_valid(pfn))
             return NULL;
         return pfn_to_page(pfn);
     }
     return iter + 1;
 }
 
 /* Memory initialisation debug and verification */
 enum mminit_level {
     MMINIT_WARNING,
     MMINIT_VERIFY,
     MMINIT_TRACE
 };
 
 #ifdef CONFIG_DEBUG_MEMORY_INIT
 
 extern int mminit_loglevel;
 
 #define mminit_dprintk(level, prefix, fmt, arg...) \
 do { \
     if (level < mminit_loglevel) { \
         if (level <= MMINIT_WARNING) \
             pr_warn("mminit::" prefix " " fmt, ##arg);  \
         else \
             printk(KERN_DEBUG "mminit::" prefix " " fmt, ##arg); \
     } \
 } while (0)
 
 extern void mminit_verify_pageflags_layout(void);
 extern void mminit_verify_zonelist(void);
 #else
 
 static inline void mminit_dprintk(enum mminit_level level,
                 const char *prefix, const char *fmt, ...)
 {
 }
 
 static inline void mminit_verify_pageflags_layout(void)
 {
 }
 
 static inline void mminit_verify_zonelist(void)
 {
 }
 #endif /* CONFIG_DEBUG_MEMORY_INIT */
 
 #define NODE_RECLAIM_NOSCAN -2
 #define NODE_RECLAIM_FULL   -1
 #define NODE_RECLAIM_SOME   0
 #define NODE_RECLAIM_SUCCESS    1
 
 #ifdef CONFIG_NUMA
 extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
 extern int find_next_best_node(int node, nodemask_t *used_node_mask);
 #else
 static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
                 unsigned int order)
 {
     return NODE_RECLAIM_NOSCAN;
 }
 static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
 {
     return NUMA_NO_NODE;
 }
 #endif
 
 /*
  * mm/memory-failure.c
  */
 extern int hwpoison_filter(struct page *p);
 
 extern u32 hwpoison_filter_dev_major;
 extern u32 hwpoison_filter_dev_minor;
 extern u64 hwpoison_filter_flags_mask;
 extern u64 hwpoison_filter_flags_value;
 extern u64 hwpoison_filter_memcg;
 extern u32 hwpoison_filter_enable;
 
 #ifdef CONFIG_MEMORY_FAILURE
 void clear_hwpoisoned_pages(struct page *memmap, int nr_pages);
 #else
 static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 {
 }
 #endif
 
 extern unsigned long  __must_check vm_mmap_pgoff(struct file *, unsigned long,
         unsigned long, unsigned long,
         unsigned long, unsigned long);
 
 extern void set_pageblock_order(void);
 unsigned int reclaim_clean_pages_from_list(struct zone *zone,
                         struct list_head *page_list);
 /* The ALLOC_WMARK bits are used as an index to zone->watermark */
 #define ALLOC_WMARK_MIN     WMARK_MIN
 #define ALLOC_WMARK_LOW     WMARK_LOW
 #define ALLOC_WMARK_HIGH    WMARK_HIGH
 #define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */
 
 /* Mask to get the watermark bits */
 #define ALLOC_WMARK_MASK    (ALLOC_NO_WATERMARKS-1)
 
 /*
  * Only MMU archs have async oom victim reclaim - aka oom_reaper so we
  * cannot assume a reduced access to memory reserves is sufficient for
  * !MMU
  */
 #ifdef CONFIG_MMU
 #define ALLOC_OOM       0x08
 #else
 #define ALLOC_OOM       ALLOC_NO_WATERMARKS
 #endif
 
 #define ALLOC_HARDER         0x10 /* try to alloc harder */
 #define ALLOC_HIGH       0x20 /* __GFP_HIGH set */
 #define ALLOC_CPUSET         0x40 /* check for correct cpuset */
 #define ALLOC_CMA        0x80 /* allow allocations from CMA areas */
 #ifdef CONFIG_ZONE_DMA32
 #define ALLOC_NOFRAGMENT    0x100 /* avoid mixing pageblock types */
 #else
 #define ALLOC_NOFRAGMENT      0x0
 #endif
 #define ALLOC_KSWAPD        0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
 
 enum ttu_flags;
 struct tlbflush_unmap_batch;
 
 
 /*
  * only for MM internal work items which do not depend on
  * any allocations or locks which might depend on allocations
  */
 extern struct workqueue_struct *mm_percpu_wq;
 
 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 void try_to_unmap_flush(void);
 void try_to_unmap_flush_dirty(void);
 void flush_tlb_batched_pending(struct mm_struct *mm);
 #else
 static inline void try_to_unmap_flush(void)
 {
 }
 static inline void try_to_unmap_flush_dirty(void)
 {
 }
 static inline void flush_tlb_batched_pending(struct mm_struct *mm)
 {
 }
 #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
 
 extern const struct trace_print_flags pageflag_names[];
 extern const struct trace_print_flags vmaflag_names[];
 extern const struct trace_print_flags gfpflag_names[];
 
 static inline bool is_migrate_highatomic(enum migratetype migratetype)
 {
     return migratetype == MIGRATE_HIGHATOMIC;
 }
 
 static inline bool is_migrate_highatomic_page(struct page *page)
 {
     return get_pageblock_migratetype(page) == MIGRATE_HIGHATOMIC;
 }
 
 void setup_zone_pageset(struct zone *zone);
 
 struct migration_target_control {
     int nid;        /* preferred node id */
     nodemask_t *nmask;
     gfp_t gfp_mask;
 };
 
 /*
  * mm/vmalloc.c
  */
 #ifdef CONFIG_MMU
 int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
                 pgprot_t prot, struct page **pages, unsigned int page_shift);
 #else
 static inline
 int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
                 pgprot_t prot, struct page **pages, unsigned int page_shift)
 {
     return -EINVAL;
 }
 #endif
 
 void vunmap_range_noflush(unsigned long start, unsigned long end);
 
 int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
               unsigned long addr, int page_nid, int *flags);
 
 void free_zone_device_page(struct page *page);
 int migrate_device_coherent_page(struct page *page);
 
 /*
  * mm/gup.c
  */
 struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
 
 DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
 extern bool mirrored_kernelcore;
 
 static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
 {
     /*
      * NOTE: we must check this before VM_SOFTDIRTY on soft-dirty
      * enablements, because when without soft-dirty being compiled in,
      * VM_SOFTDIRTY is defined as 0x0, then !(vm_flags & VM_SOFTDIRTY)
      * will be constantly true.
      */
     if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
         return false;
 
     /*
      * Soft-dirty is kind of special: its tracking is enabled when the
      * vma flags not set.
      */
     return !(vma->vm_flags & VM_SOFTDIRTY);
 }
 
 #endif  /* __MM_INTERNAL_H */

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