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    Subject[PATCH v14 013/138] mm/filemap: Add folio_index(), folio_file_page() and folio_contains()
    Date
    folio_index() is the equivalent of page_index() for folios.
    folio_file_page() is the equivalent of find_subpage().
    folio_contains() is the equivalent of thp_contains().

    No changes to generated code.

    Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Acked-by: Jeff Layton <jlayton@kernel.org>
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Acked-by: Vlastimil Babka <vbabka@suse.cz>
    Reviewed-by: William Kucharski <william.kucharski@oracle.com>
    Reviewed-by: David Howells <dhowells@redhat.com>
    ---
    include/linux/pagemap.h | 56 +++++++++++++++++++++++++++++++++++++++++
    1 file changed, 56 insertions(+)

    diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
    index 3279c731ee04..f7c165b5991f 100644
    --- a/include/linux/pagemap.h
    +++ b/include/linux/pagemap.h
    @@ -386,6 +386,62 @@ static inline bool thp_contains(struct page *head, pgoff_t index)
    return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
    }

    +#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_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
    --
    2.30.2
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