Message-Id: <20220613053715.2394147-5-hch@lst.de>
Date:   Mon, 13 Jun 2022 07:37:13 +0200
From:   Christoph Hellwig <hch@....de>
To:     Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.com>,
        Dave Kleikamp <shaggy@...nel.org>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        ntfs3@...ts.linux.dev, Jan Kara <jack@...e.cz>
Subject: [PATCH 4/6] fs: remove the nobh helpers

All callers are gone, so remove the now dead code.

Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jan Kara <jack@...e.cz>
---
 fs/buffer.c                 | 324 ------------------------------------
 fs/mpage.c                  |  25 +--
 include/linux/buffer_head.h |   8 -
 include/linux/mpage.h       |   2 -
 4 files changed, 1 insertion(+), 358 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index ce9844d7c10fa..5717d1881d2fa 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2537,330 +2537,6 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL(block_page_mkwrite);
 
-/*
- * nobh_write_begin()'s prereads are special: the buffer_heads are freed
- * immediately, while under the page lock.  So it needs a special end_io
- * handler which does not touch the bh after unlocking it.
- */
-static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
-{
-	__end_buffer_read_notouch(bh, uptodate);
-}
-
-/*
- * Attach the singly-linked list of buffers created by nobh_write_begin, to
- * the page (converting it to circular linked list and taking care of page
- * dirty races).
- */
-static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
-{
-	struct buffer_head *bh;
-
-	BUG_ON(!PageLocked(page));
-
-	spin_lock(&page->mapping->private_lock);
-	bh = head;
-	do {
-		if (PageDirty(page))
-			set_buffer_dirty(bh);
-		if (!bh->b_this_page)
-			bh->b_this_page = head;
-		bh = bh->b_this_page;
-	} while (bh != head);
-	attach_page_private(page, head);
-	spin_unlock(&page->mapping->private_lock);
-}
-
-/*
- * On entry, the page is fully not uptodate.
- * On exit the page is fully uptodate in the areas outside (from,to)
- * The filesystem needs to handle block truncation upon failure.
- */
-int nobh_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
-			struct page **pagep, void **fsdata,
-			get_block_t *get_block)
-{
-	struct inode *inode = mapping->host;
-	const unsigned blkbits = inode->i_blkbits;
-	const unsigned blocksize = 1 << blkbits;
-	struct buffer_head *head, *bh;
-	struct page *page;
-	pgoff_t index;
-	unsigned from, to;
-	unsigned block_in_page;
-	unsigned block_start, block_end;
-	sector_t block_in_file;
-	int nr_reads = 0;
-	int ret = 0;
-	int is_mapped_to_disk = 1;
-
-	index = pos >> PAGE_SHIFT;
-	from = pos & (PAGE_SIZE - 1);
-	to = from + len;
-
-	page = grab_cache_page_write_begin(mapping, index);
-	if (!page)
-		return -ENOMEM;
-	*pagep = page;
-	*fsdata = NULL;
-
-	if (page_has_buffers(page)) {
-		ret = __block_write_begin(page, pos, len, get_block);
-		if (unlikely(ret))
-			goto out_release;
-		return ret;
-	}
-
-	if (PageMappedToDisk(page))
-		return 0;
-
-	/*
-	 * Allocate buffers so that we can keep track of state, and potentially
-	 * attach them to the page if an error occurs. In the common case of
-	 * no error, they will just be freed again without ever being attached
-	 * to the page (which is all OK, because we're under the page lock).
-	 *
-	 * Be careful: the buffer linked list is a NULL terminated one, rather
-	 * than the circular one we're used to.
-	 */
-	head = alloc_page_buffers(page, blocksize, false);
-	if (!head) {
-		ret = -ENOMEM;
-		goto out_release;
-	}
-
-	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
-
-	/*
-	 * We loop across all blocks in the page, whether or not they are
-	 * part of the affected region.  This is so we can discover if the
-	 * page is fully mapped-to-disk.
-	 */
-	for (block_start = 0, block_in_page = 0, bh = head;
-		  block_start < PAGE_SIZE;
-		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
-		int create;
-
-		block_end = block_start + blocksize;
-		bh->b_state = 0;
-		create = 1;
-		if (block_start >= to)
-			create = 0;
-		ret = get_block(inode, block_in_file + block_in_page,
-					bh, create);
-		if (ret)
-			goto failed;
-		if (!buffer_mapped(bh))
-			is_mapped_to_disk = 0;
-		if (buffer_new(bh))
-			clean_bdev_bh_alias(bh);
-		if (PageUptodate(page)) {
-			set_buffer_uptodate(bh);
-			continue;
-		}
-		if (buffer_new(bh) || !buffer_mapped(bh)) {
-			zero_user_segments(page, block_start, from,
-							to, block_end);
-			continue;
-		}
-		if (buffer_uptodate(bh))
-			continue;	/* reiserfs does this */
-		if (block_start < from || block_end > to) {
-			lock_buffer(bh);
-			bh->b_end_io = end_buffer_read_nobh;
-			submit_bh(REQ_OP_READ, 0, bh);
-			nr_reads++;
-		}
-	}
-
-	if (nr_reads) {
-		/*
-		 * The page is locked, so these buffers are protected from
-		 * any VM or truncate activity.  Hence we don't need to care
-		 * for the buffer_head refcounts.
-		 */
-		for (bh = head; bh; bh = bh->b_this_page) {
-			wait_on_buffer(bh);
-			if (!buffer_uptodate(bh))
-				ret = -EIO;
-		}
-		if (ret)
-			goto failed;
-	}
-
-	if (is_mapped_to_disk)
-		SetPageMappedToDisk(page);
-
-	*fsdata = head; /* to be released by nobh_write_end */
-
-	return 0;
-
-failed:
-	BUG_ON(!ret);
-	/*
-	 * Error recovery is a bit difficult. We need to zero out blocks that
-	 * were newly allocated, and dirty them to ensure they get written out.
-	 * Buffers need to be attached to the page at this point, otherwise
-	 * the handling of potential IO errors during writeout would be hard
-	 * (could try doing synchronous writeout, but what if that fails too?)
-	 */
-	attach_nobh_buffers(page, head);
-	page_zero_new_buffers(page, from, to);
-
-out_release:
-	unlock_page(page);
-	put_page(page);
-	*pagep = NULL;
-
-	return ret;
-}
-EXPORT_SYMBOL(nobh_write_begin);
-
-int nobh_write_end(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len, unsigned copied,
-			struct page *page, void *fsdata)
-{
-	struct inode *inode = page->mapping->host;
-	struct buffer_head *head = fsdata;
-	struct buffer_head *bh;
-	BUG_ON(fsdata != NULL && page_has_buffers(page));
-
-	if (unlikely(copied < len) && head)
-		attach_nobh_buffers(page, head);
-	if (page_has_buffers(page))
-		return generic_write_end(file, mapping, pos, len,
-					copied, page, fsdata);
-
-	SetPageUptodate(page);
-	set_page_dirty(page);
-	if (pos+copied > inode->i_size) {
-		i_size_write(inode, pos+copied);
-		mark_inode_dirty(inode);
-	}
-
-	unlock_page(page);
-	put_page(page);
-
-	while (head) {
-		bh = head;
-		head = head->b_this_page;
-		free_buffer_head(bh);
-	}
-
-	return copied;
-}
-EXPORT_SYMBOL(nobh_write_end);
-
-/*
- * nobh_writepage() - based on block_full_write_page() except
- * that it tries to operate without attaching bufferheads to
- * the page.
- */
-int nobh_writepage(struct page *page, get_block_t *get_block,
-			struct writeback_control *wbc)
-{
-	struct inode * const inode = page->mapping->host;
-	loff_t i_size = i_size_read(inode);
-	const pgoff_t end_index = i_size >> PAGE_SHIFT;
-	unsigned offset;
-	int ret;
-
-	/* Is the page fully inside i_size? */
-	if (page->index < end_index)
-		goto out;
-
-	/* Is the page fully outside i_size? (truncate in progress) */
-	offset = i_size & (PAGE_SIZE-1);
-	if (page->index >= end_index+1 || !offset) {
-		unlock_page(page);
-		return 0; /* don't care */
-	}
-
-	/*
-	 * The page straddles i_size.  It must be zeroed out on each and every
-	 * writepage invocation because it may be mmapped.  "A file is mapped
-	 * in multiples of the page size.  For a file that is not a multiple of
-	 * the  page size, the remaining memory is zeroed when mapped, and
-	 * writes to that region are not written out to the file."
-	 */
-	zero_user_segment(page, offset, PAGE_SIZE);
-out:
-	ret = mpage_writepage(page, get_block, wbc);
-	if (ret == -EAGAIN)
-		ret = __block_write_full_page(inode, page, get_block, wbc,
-					      end_buffer_async_write);
-	return ret;
-}
-EXPORT_SYMBOL(nobh_writepage);
-
-int nobh_truncate_page(struct address_space *mapping,
-			loff_t from, get_block_t *get_block)
-{
-	pgoff_t index = from >> PAGE_SHIFT;
-	struct inode *inode = mapping->host;
-	unsigned blocksize = i_blocksize(inode);
-	struct folio *folio;
-	struct buffer_head map_bh;
-	size_t offset;
-	sector_t iblock;
-	int err;
-
-	/* Block boundary? Nothing to do */
-	if (!(from & (blocksize - 1)))
-		return 0;
-
-	folio = __filemap_get_folio(mapping, index, FGP_LOCK | FGP_CREAT,
-			mapping_gfp_mask(mapping));
-	err = -ENOMEM;
-	if (!folio)
-		goto out;
-
-	if (folio_buffers(folio))
-		goto has_buffers;
-
-	iblock = from >> inode->i_blkbits;
-	map_bh.b_size = blocksize;
-	map_bh.b_state = 0;
-	err = get_block(inode, iblock, &map_bh, 0);
-	if (err)
-		goto unlock;
-	/* unmapped? It's a hole - nothing to do */
-	if (!buffer_mapped(&map_bh))
-		goto unlock;
-
-	/* Ok, it's mapped. Make sure it's up-to-date */
-	if (!folio_test_uptodate(folio)) {
-		err = mapping->a_ops->read_folio(NULL, folio);
-		if (err) {
-			folio_put(folio);
-			goto out;
-		}
-		folio_lock(folio);
-		if (!folio_test_uptodate(folio)) {
-			err = -EIO;
-			goto unlock;
-		}
-		if (folio_buffers(folio))
-			goto has_buffers;
-	}
-	offset = offset_in_folio(folio, from);
-	folio_zero_segment(folio, offset, round_up(offset, blocksize));
-	folio_mark_dirty(folio);
-	err = 0;
-
-unlock:
-	folio_unlock(folio);
-	folio_put(folio);
-out:
-	return err;
-
-has_buffers:
-	folio_unlock(folio);
-	folio_put(folio);
-	return block_truncate_page(mapping, from, get_block);
-}
-EXPORT_SYMBOL(nobh_truncate_page);
-
 int block_truncate_page(struct address_space *mapping,
 			loff_t from, get_block_t *get_block)
 {
diff --git a/fs/mpage.c b/fs/mpage.c
index 0d25f44f5707c..31a97a0acf5f5 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -402,7 +402,6 @@ struct mpage_data {
 	struct bio *bio;
 	sector_t last_block_in_bio;
 	get_block_t *get_block;
-	unsigned use_writepage;
 };
 
 /*
@@ -622,15 +621,10 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
 	if (bio)
 		bio = mpage_bio_submit(bio);
 
-	if (mpd->use_writepage) {
-		ret = mapping->a_ops->writepage(page, wbc);
-	} else {
-		ret = -EAGAIN;
-		goto out;
-	}
 	/*
 	 * The caller has a ref on the inode, so *mapping is stable
 	 */
+	ret = mapping->a_ops->writepage(page, wbc);
 	mapping_set_error(mapping, ret);
 out:
 	mpd->bio = bio;
@@ -672,7 +666,6 @@ mpage_writepages(struct address_space *mapping,
 			.bio = NULL,
 			.last_block_in_bio = 0,
 			.get_block = get_block,
-			.use_writepage = 1,
 		};
 
 		ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
@@ -683,19 +676,3 @@ mpage_writepages(struct address_space *mapping,
 	return ret;
 }
 EXPORT_SYMBOL(mpage_writepages);
-
-int mpage_writepage(struct page *page, get_block_t get_block,
-	struct writeback_control *wbc)
-{
-	struct mpage_data mpd = {
-		.bio = NULL,
-		.last_block_in_bio = 0,
-		.get_block = get_block,
-		.use_writepage = 0,
-	};
-	int ret = __mpage_writepage(page, wbc, &mpd);
-	if (mpd.bio)
-		mpage_bio_submit(mpd.bio);
-	return ret;
-}
-EXPORT_SYMBOL(mpage_writepage);
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index b0366c89d6a4d..61afb81cfdaea 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -258,14 +258,6 @@ static inline vm_fault_t block_page_mkwrite_return(int err)
 }
 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
-int nobh_write_begin(struct address_space *, loff_t, unsigned len,
-				struct page **, void **, get_block_t*);
-int nobh_write_end(struct file *, struct address_space *,
-				loff_t, unsigned, unsigned,
-				struct page *, void *);
-int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
-int nobh_writepage(struct page *page, get_block_t *get_block,
-                        struct writeback_control *wbc);
 
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_folio(struct address_space *,
diff --git a/include/linux/mpage.h b/include/linux/mpage.h
index 43986f7ec4dd3..1bdc39daac0a3 100644
--- a/include/linux/mpage.h
+++ b/include/linux/mpage.h
@@ -19,7 +19,5 @@ void mpage_readahead(struct readahead_control *, get_block_t get_block);
 int mpage_read_folio(struct folio *folio, get_block_t get_block);
 int mpage_writepages(struct address_space *mapping,
 		struct writeback_control *wbc, get_block_t get_block);
-int mpage_writepage(struct page *page, get_block_t *get_block,
-		struct writeback_control *wbc);
 
 #endif
-- 
2.30.2

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