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    Subject[PATCH v2 35/46] mm/filemap: Add folio_mkwrite_check_truncate()
    Date
    This is the folio equivalent of page_mkwrite_check_truncate().

    Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    ---
    include/linux/pagemap.h | 28 ++++++++++++++++++++++++++++
    1 file changed, 28 insertions(+)

    diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
    index c30db827b65d..14f0c5260234 100644
    --- a/include/linux/pagemap.h
    +++ b/include/linux/pagemap.h
    @@ -1120,6 +1120,34 @@ static inline unsigned long dir_pages(struct inode *inode)
    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
    --
    2.30.2
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