From 0217fbb0271a7c78e16629cf45375916ec2eb35f Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Mon, 16 Oct 2023 21:10:52 +0100 Subject: buffer: add get_nth_bh() Extract this useful helper from nilfs_page_get_nth_block() Link: https://lkml.kernel.org/r/20231016201114.1928083-6-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Ryusuke Konishi Cc: Andreas Gruenbacher Cc: Pankaj Raghav Signed-off-by: Andrew Morton --- include/linux/buffer_head.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/linux/buffer_head.h') diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 1001244a8941..3d85a0cf0ca5 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 __must_check +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 -- cgit v1.2.3