v4.19.13 snapshot.
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
new file mode 100644
index 0000000..b1bd218
--- /dev/null
+++ b/include/linux/pagemap.h
@@ -0,0 +1,648 @@
+/* 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 pagevec;
+
+/*
+ * 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);
+
+/*
+ * 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 the i_pages lock held):
+ * 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 a 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 gfp_t readahead_gfp_mask(struct address_space *x)
+{
+ return mapping_gfp_mask(x) | __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_range_tag(struct address_space *mapping, pgoff_t *index,
+ pgoff_t end, int tag, unsigned int nr_pages,
+ struct page **pages);
+static inline unsigned find_get_pages_tag(struct address_space *mapping,
+ pgoff_t *index, int tag, unsigned int nr_pages,
+ struct page **pages)
+{
+ return find_get_pages_range_tag(mapping, index, (pgoff_t)-1, tag,
+ nr_pages, 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);
+void delete_from_page_cache_batch(struct address_space *mapping,
+ struct pagevec *pvec);
+
+/*
+ * 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 */