From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Matthew Wilcox (Oracle)" Subject: [PATCH 04/26] buffer: Add get_nth_bh() Date: Tue, 19 Sep 2023 05:51:13 +0100 Message-ID: <20230919045135.3635437-5-willy@infradead.org> References: <20230919045135.3635437-1-willy@infradead.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=nArwds4hDHBhHYufta7EFXQvOR30NKKhjUtIyvFznt4=; b=RTTNLwriDilS/kAKdKH3GwxU+Z 7jktCZAGBgGUmuWIt+5Pse+UewyOWiwO3uXEu8zXRi4MU3iF27q0hSUVvxkGsxkrXyyodbljvAcTp 0LMy4wLm7Of+4x8zyZiuxQCq/rSIpgFdS8Wi2Vjs0saHDOwl9OPAP5MHyEcN0pkK3zuOeVDeN+J6f 9LIzJ1L7U+P7GbH6ABVZJvsvhPtasrFVv307p1uIJDRigSb7QqthAk0YeppXMZvCx6gCNKIr5soCQ TPdbgB84XvpOr5H3RR/9eBDj9R540Bb/LAdli8aC/6jB6QiZLjbt7Mg6a/GJxGfSxBpI87NOJLLrD VfuCNkWA==; In-Reply-To: <20230919045135.3635437-1-willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" To: Andrew Morton Cc: "Matthew Wilcox (Oracle)" , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, gfs2-cunTk1MwBs/YUNznpcFYbw@public.gmane.org, linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ntfs-dev-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, ntfs3-cunTk1MwBs/YUNznpcFYbw@public.gmane.org, ocfs2-devel-cunTk1MwBs/YUNznpcFYbw@public.gmane.org, reiserfs-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Pankaj Raghav Extract this useful helper from nilfs_page_get_nth_block() Signed-off-by: Matthew Wilcox (Oracle) --- 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