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Message-Id: <20230919045135.3635437-5-willy@infradead.org> Date: Tue, 19 Sep 2023 05:51:13 +0100 From: "Matthew Wilcox (Oracle)" <willy@...radead.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-fsdevel@...r.kernel.org, gfs2@...ts.linux.dev, linux-nilfs@...r.kernel.org, linux-ntfs-dev@...ts.sourceforge.net, ntfs3@...ts.linux.dev, ocfs2-devel@...ts.linux.dev, reiserfs-devel@...r.kernel.org, linux-ext4@...r.kernel.org, Pankaj Raghav <p.raghav@...sung.com> Subject: [PATCH 04/26] buffer: Add get_nth_bh() Extract this useful helper from nilfs_page_get_nth_block() Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> --- 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
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