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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org
Subject: [PATCH 2/7] fs: Supply optional buffered_write_operations in buffer.c
Date: Tue, 28 May 2024 17:48:23 +0100
Message-ID: <20240528164829.2105447-3-willy@infradead.org>
In-Reply-To: <20240528164829.2105447-1-willy@infradead.org>
References: <20240528164829.2105447-1-willy@infradead.org>
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generic_cont_expand_simple() and cont_expand_zero() currently call
->write_begin and ->write_end, so will also need to be converted to
use buffered_write_operations.  Use macro magic to pass NULL if no
buffered_write_operations is supplied.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/buffer.c                 | 78 ++++++++++++++++++++++++++-----------
 include/linux/buffer_head.h | 22 +++++++++--
 2 files changed, 74 insertions(+), 26 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 8c19e705b9c3..58ac52f20bf6 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2466,23 +2466,32 @@ EXPORT_SYMBOL(block_read_full_folio);
  * truncates.  Uses filesystem pagecache writes to allow the filesystem to
  * deal with the hole.  
  */
-int generic_cont_expand_simple(struct inode *inode, loff_t size)
+int generic_cont_expand_simple(struct inode *inode, loff_t size,
+		const struct buffered_write_operations *ops, void *fsdata)
 {
 	struct address_space *mapping = inode->i_mapping;
 	const struct address_space_operations *aops = mapping->a_ops;
 	struct page *page;
-	void *fsdata = NULL;
+	struct folio *folio;
 	int err;
 
 	err = inode_newsize_ok(inode, size);
 	if (err)
 		goto out;
 
-	err = aops->write_begin(NULL, mapping, size, 0, &page, &fsdata);
+	if (ops) {
+		folio = ops->write_begin(NULL, mapping, size, 0, &fsdata);
+		if (IS_ERR(folio))
+			err = PTR_ERR(folio);
+	} else
+		err = aops->write_begin(NULL, mapping, size, 0, &page, &fsdata);
 	if (err)
 		goto out;
 
-	err = aops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
+	if (ops)
+		err = ops->write_end(NULL, mapping, size, 0, 0, folio, &fsdata);
+	else
+		err = aops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
 	BUG_ON(err > 0);
 
 out:
@@ -2491,13 +2500,14 @@ int generic_cont_expand_simple(struct inode *inode, loff_t size)
 EXPORT_SYMBOL(generic_cont_expand_simple);
 
 static int cont_expand_zero(struct file *file, struct address_space *mapping,
-			    loff_t pos, loff_t *bytes)
+		loff_t pos, loff_t *bytes,
+		const struct buffered_write_operations *ops, void **fsdata)
 {
 	struct inode *inode = mapping->host;
 	const struct address_space_operations *aops = mapping->a_ops;
 	unsigned int blocksize = i_blocksize(inode);
 	struct page *page;
-	void *fsdata = NULL;
+	struct folio *folio;
 	pgoff_t index, curidx;
 	loff_t curpos;
 	unsigned zerofrom, offset, len;
@@ -2514,13 +2524,25 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
 		}
 		len = PAGE_SIZE - zerofrom;
 
-		err = aops->write_begin(file, mapping, curpos, len,
-					    &page, &fsdata);
-		if (err)
-			goto out;
+		if (ops) {
+			folio = ops->write_begin(file, mapping, curpos, len,
+					fsdata);
+			if (IS_ERR(folio))
+				return PTR_ERR(folio);
+			page = &folio->page;
+		} else {
+			err = aops->write_begin(file, mapping, curpos, len,
+					&page, fsdata);
+			if (err)
+				goto out;
+		}
 		zero_user(page, zerofrom, len);
-		err = aops->write_end(file, mapping, curpos, len, len,
-						page, fsdata);
+		if (ops)
+			err = ops->write_end(file, mapping, curpos, len, len,
+					folio, fsdata);
+		else
+			err = aops->write_end(file, mapping, curpos, len, len,
+					page, *fsdata);
 		if (err < 0)
 			goto out;
 		BUG_ON(err != len);
@@ -2547,13 +2569,25 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
 		}
 		len = offset - zerofrom;
 
-		err = aops->write_begin(file, mapping, curpos, len,
-					    &page, &fsdata);
-		if (err)
-			goto out;
+		if (ops) {
+			folio = ops->write_begin(file, mapping, curpos, len,
+					fsdata);
+			if (IS_ERR(folio))
+				return PTR_ERR(folio);
+			page = &folio->page;
+		} else {
+			err = aops->write_begin(file, mapping, curpos, len,
+					&page, fsdata);
+			if (err)
+				goto out;
+		}
 		zero_user(page, zerofrom, len);
-		err = aops->write_end(file, mapping, curpos, len, len,
-						page, fsdata);
+		if (ops)
+			err = ops->write_end(file, mapping, curpos, len, len,
+					folio, fsdata);
+		else
+			err = aops->write_end(file, mapping, curpos, len, len,
+					page, *fsdata);
 		if (err < 0)
 			goto out;
 		BUG_ON(err != len);
@@ -2568,16 +2602,16 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
  * We may have to extend the file.
  */
 int cont_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len,
-			struct page **pagep, void **fsdata,
-			get_block_t *get_block, loff_t *bytes)
+		loff_t pos, unsigned len, struct page **pagep, void **fsdata,
+		get_block_t *get_block, loff_t *bytes,
+		const struct buffered_write_operations *ops)
 {
 	struct inode *inode = mapping->host;
 	unsigned int blocksize = i_blocksize(inode);
 	unsigned int zerofrom;
 	int err;
 
-	err = cont_expand_zero(file, mapping, pos, bytes);
+	err = cont_expand_zero(file, mapping, pos, bytes, ops, fsdata);
 	if (err)
 		return err;
 
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index e022e40b099e..1b7f14e39ab8 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -268,16 +268,30 @@ int generic_write_end(struct file *, struct address_space *,
 				loff_t, unsigned, unsigned,
 				struct page *, void *);
 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to);
-int cont_write_begin(struct file *, struct address_space *, loff_t,
-			unsigned, struct page **, void **,
-			get_block_t *, loff_t *);
-int generic_cont_expand_simple(struct inode *inode, loff_t size);
+int cont_write_begin(struct file *, struct address_space *, loff_t pos,
+		unsigned len, struct page **, void **fsdata, get_block_t *,
+		loff_t *bytes, const struct buffered_write_operations *);
+int generic_cont_expand_simple(struct inode *inode, loff_t size,
+		const struct buffered_write_operations *ops, void *fsdata);
 void block_commit_write(struct page *page, unsigned int from, unsigned int to);
 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 				get_block_t get_block);
 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 *);
 
+#define _cont_write_begin(file, mapping, pos, len, pagep, fsdata,	\
+		getblk, bytes, ops, extra...)				\
+	cont_write_begin(file, mapping, pos, len, pagep, fsdata,	\
+		getblk, bytes, ops)
+#define cont_write_begin(file, mapping, pos, len, pagep, fsdata,	\
+		getblk, bytes, ops...)					\
+	_cont_write_begin(file, mapping, pos, len, pagep, fsdata,	\
+		getblk, bytes, ## ops, NULL)
+#define _generic_cont_expand_simple(inode, size, ops, fsdata, extra...)	\
+	generic_cont_expand_simple(inode, size, ops, fsdata)
+#define generic_cont_expand_simple(inode, size, ops_data...)		\
+	_generic_cont_expand_simple(inode, size, ## ops_data, NULL, NULL)
+
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_folio(struct address_space *,
 		struct folio *dst, struct folio *src, enum migrate_mode);
-- 
2.43.0