+ buffer-add-get_nth_bh.patch added to mm-unstable branch

+ buffer-add-get_nth_bh.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: buffer: add get_nth_bh()
has been added to the -mm mm-unstable branch.  Its filename is
     buffer-add-get_nth_bh.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/buffer-add-get_nth_bh.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: buffer: add get_nth_bh()
Date: Mon, 16 Oct 2023 21:10:52 +0100

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) <willy@infradead.org>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/nilfs2/page.h            |    7 +------
 include/linux/buffer_head.h |   22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

--- a/fs/nilfs2/page.h~buffer-add-get_nth_bh
+++ a/fs/nilfs2/page.h
@@ -55,12 +55,7 @@ unsigned long nilfs_find_uncommitted_ext
 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 */
--- a/include/linux/buffer_head.h~buffer-add-get_nth_bh
+++ a/include/linux/buffer_head.h
@@ -457,6 +457,28 @@ __bread(struct block_device *bdev, secto
 	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
_

Patches currently in -mm which might be from willy@infradead.org are

mm-make-lock_folio_maybe_drop_mmap-vma-lock-aware.patch
mm-call-wp_page_copy-under-the-vma-lock.patch
mm-handle-shared-faults-under-the-vma-lock.patch
mm-handle-cow-faults-under-the-vma-lock.patch
mm-handle-read-faults-under-the-vma-lock.patch
mm-handle-write-faults-to-ro-pages-under-the-vma-lock.patch
iomap-hold-state_lock-over-call-to-ifs_set_range_uptodate.patch
iomap-protect-read_bytes_pending-with-the-state_lock.patch
mm-add-folio_end_read.patch
ext4-use-folio_end_read.patch
buffer-use-folio_end_read.patch
iomap-use-folio_end_read.patch
bitops-add-xor_unlock_is_negative_byte.patch
alpha-implement-xor_unlock_is_negative_byte.patch
m68k-implement-xor_unlock_is_negative_byte.patch
mips-implement-xor_unlock_is_negative_byte.patch
powerpc-implement-arch_xor_unlock_is_negative_byte-on-32-bit.patch
riscv-implement-xor_unlock_is_negative_byte.patch
s390-implement-arch_xor_unlock_is_negative_byte.patch
mm-delete-checks-for-xor_unlock_is_negative_byte.patch
mm-add-folio_xor_flags_has_waiters.patch
mm-make-__end_folio_writeback-return-void.patch
mm-use-folio_xor_flags_has_waiters-in-folio_end_writeback.patch
filemap-remove-use-of-wait-bookmarks.patch
sched-remove-wait-bookmarks.patch
buffer-return-bool-from-grow_dev_folio.patch
buffer-make-folio_create_empty_buffers-return-a-buffer_head.patch
mpage-convert-map_buffer_to_folio-to-folio_create_empty_buffers.patch
ext4-convert-to-folio_create_empty_buffers.patch
buffer-add-get_nth_bh.patch
gfs2-convert-inode-unstuffing-to-use-a-folio.patch
gfs2-convert-gfs2_getbuf-to-folios.patch
gfs2-convert-gfs2_getjdatabuf-to-use-a-folio.patch
gfs2-convert-gfs2_write_buf_to_page-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_freeze_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_grab_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_copy_page-to-nilfs_copy_folio.patch
nilfs2-convert-nilfs_mdt_forget_block-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_get_frozen_buffer-to-use-a-folio.patch
nilfs2-remove-nilfs_page_get_nth_block.patch
nilfs2-convert-nilfs_lookup_dirty_data_buffers-to-use-folio_create_empty_buffers.patch
ntfs-convert-ntfs_read_block-to-use-a-folio.patch
ntfs-convert-ntfs_writepage-to-use-a-folio.patch
ntfs-convert-ntfs_prepare_pages_for_non_resident_write-to-folios.patch
ntfs3-convert-ntfs_zero_range-to-use-a-folio.patch
ocfs2-convert-ocfs2_map_page_blocks-to-use-a-folio.patch
reiserfs-convert-writepage-to-use-a-folio.patch
ufs-add-ufs_get_locked_folio-and-ufs_put_locked_folio.patch
ufs-use-ufs_get_locked_folio-in-ufs_alloc_lastblock.patch
ufs-convert-ufs_change_blocknr-to-use-folios.patch
ufs-remove-ufs_get_locked_page.patch
buffer-remove-folio_create_empty_buffers.patch