On Tue, Sep 19, 2023 at 4:20 PM Matthew Wilcox (Oracle) wrote:
>
> Extract this useful helper from nilfs_page_get_nth_block()
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
> fs/nilfs2/page.h | 7 +------
> include/linux/buffer_head.h | 22 ++++++++++++++++++++++
> 2 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
> index 21ddcdd4d63e..344d71942d36 100644
> --- a/fs/nilfs2/page.h
> +++ b/fs/nilfs2/page.h
> @@ -55,12 +55,7 @@ unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
> static inline struct buffer_head *
> nilfs_page_get_nth_block(struct page *page, unsigned int count)
> {
> - struct buffer_head *bh = page_buffers(page);
> -
> - while (count-- > 0)
> - bh = bh->b_this_page;
> - get_bh(bh);
> - return bh;
> + return get_nth_bh(page_buffers(page), count);
> }
>
> #endif /* _NILFS_PAGE_H */
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index 1001244a8941..9fc615ee17fd 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -457,6 +457,28 @@ __bread(struct block_device *bdev, sector_t block, unsigned size)
> return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
> }
>
> +/**
> + * get_nth_bh - Get a reference on the n'th buffer after this one.
> + * @bh: The buffer to start counting from.
> + * @count: How many buffers to skip.
> + *
> + * This is primarily useful for finding the nth buffer in a folio; in
> + * that case you pass the head buffer and the byte offset in the folio
> + * divided by the block size. It can be used for other purposes, but
> + * it will wrap at the end of the folio rather than returning NULL or
> + * proceeding to the next folio for you.
> + *
> + * Return: The requested buffer with an elevated refcount.
> + */
> +static inline struct buffer_head *get_nth_bh(struct buffer_head *bh,
> + unsigned int count)
> +{
> + while (count--)
> + bh = bh->b_this_page;
> + get_bh(bh);
> + return bh;
> +}
> +
> bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
>
> #ifdef CONFIG_BUFFER_HEAD
> --
> 2.40.1
>
Acked-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Looks good to me.
Thanks,
Ryusuke Konishi
