remove the nobh helpers v2

remove the nobh helpers v2

[Christoph Hellwig]

Hi all,

this series (against the pagecache for-next branch) removes the nobh
helpers which are a variant of the "normal" buffer head helpers with
special tradeoffs for machines with a lot of highmem, and thus rather
obsolete.  They pass xfstests, or in case of jfs at least get as far
as the baseline.

This might not be as nice as an actual iomap conversion, but already
removes some hairy code in the way of removing ->writepage.

Changes since v1:
 - handle non-resident data in ->writepages in ntfs3 properly

Diffstat:
 Documentation/filesystems/ext2.rst |    2 
 fs/buffer.c                        |  324 -------------------------------------
 fs/ext2/ext2.h                     |    1 
 fs/ext2/inode.c                    |   51 -----
 fs/ext2/namei.c                    |   10 -
 fs/ext2/super.c                    |    6 
 fs/jfs/inode.c                     |   18 +-
 fs/mpage.c                         |   47 -----
 fs/ntfs3/inode.c                   |    8 
 include/linux/buffer_head.h        |    8 
 include/linux/mpage.h              |    2 
 11 files changed, 32 insertions(+), 445 deletions(-)

[PATCH 1/6] ntfs3: refactor ntfs_writepages

[Christoph Hellwig]

Handle the resident case with an explicit generic_writepages call instead
of using the obscure overload that makes mpage_writepages with a NULL
get_block do the same thing.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/ntfs3/inode.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
index be4ebdd8048b0..28c09c25b823d 100644
--- a/fs/ntfs3/inode.c
+++ b/fs/ntfs3/inode.c
@@ -851,12 +851,10 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
 static int ntfs_writepages(struct address_space *mapping,
 			   struct writeback_control *wbc)
 {
-	struct inode *inode = mapping->host;
-	struct ntfs_inode *ni = ntfs_i(inode);
 	/* Redirect call to 'ntfs_writepage' for resident files. */
-	get_block_t *get_block = is_resident(ni) ? NULL : &ntfs_get_block;
-
-	return mpage_writepages(mapping, wbc, get_block);
+	if (is_resident(ntfs_i(mapping->host)))
+		return generic_writepages(mapping, wbc);
+	return mpage_writepages(mapping, wbc, ntfs_get_block);
 }
 
 static int ntfs_get_block_write_begin(struct inode *inode, sector_t vbn,
-- 
2.30.2

Re: [PATCH 1/6] ntfs3: refactor ntfs_writepages

[Jan Kara]

On Mon 13-06-22 07:37:10, Christoph Hellwig wrote:
> Handle the resident case with an explicit generic_writepages call instead
> of using the obscure overload that makes mpage_writepages with a NULL
> get_block do the same thing.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Yeah, much more obvious :). Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ntfs3/inode.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
> index be4ebdd8048b0..28c09c25b823d 100644
> --- a/fs/ntfs3/inode.c
> +++ b/fs/ntfs3/inode.c
> @@ -851,12 +851,10 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
>  static int ntfs_writepages(struct address_space *mapping,
>  			   struct writeback_control *wbc)
>  {
> -	struct inode *inode = mapping->host;
> -	struct ntfs_inode *ni = ntfs_i(inode);
>  	/* Redirect call to 'ntfs_writepage' for resident files. */
> -	get_block_t *get_block = is_resident(ni) ? NULL : &ntfs_get_block;
> -
> -	return mpage_writepages(mapping, wbc, get_block);
> +	if (is_resident(ntfs_i(mapping->host)))
> +		return generic_writepages(mapping, wbc);
> +	return mpage_writepages(mapping, wbc, ntfs_get_block);
>  }
>  
>  static int ntfs_get_block_write_begin(struct inode *inode, sector_t vbn,
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

[PATCH 2/6] ext2: remove nobh support

[Christoph Hellwig]

The nobh mode is an obscure feature to save lowlevel for large memory
32-bit configurations while trading for much slower performance and
has been long obsolete.  Remove it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 Documentation/filesystems/ext2.rst |  2 --
 fs/ext2/ext2.h                     |  1 -
 fs/ext2/inode.c                    | 51 ++----------------------------
 fs/ext2/namei.c                    | 10 ++----
 fs/ext2/super.c                    |  6 ++--
 5 files changed, 7 insertions(+), 63 deletions(-)

diff --git a/Documentation/filesystems/ext2.rst b/Documentation/filesystems/ext2.rst
index 154101cf0e4f5..92aae683e16a7 100644
--- a/Documentation/filesystems/ext2.rst
+++ b/Documentation/filesystems/ext2.rst
@@ -59,8 +59,6 @@ acl				Enable POSIX Access Control Lists support
 				(requires CONFIG_EXT2_FS_POSIX_ACL).
 noacl				Don't support POSIX ACLs.
 
-nobh				Do not attach buffer_heads to file pagecache.
-
 quota, usrquota			Enable user disk quota support
 				(requires CONFIG_QUOTA).
 
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index d4f306aa5aceb..28de11a22e5f6 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -795,7 +795,6 @@ extern const struct file_operations ext2_file_operations;
 /* inode.c */
 extern void ext2_set_file_ops(struct inode *inode);
 extern const struct address_space_operations ext2_aops;
-extern const struct address_space_operations ext2_nobh_aops;
 extern const struct iomap_ops ext2_iomap_ops;
 
 /* namei.c */
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 58a9d061f17d1..c5229033baf05 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -908,25 +908,6 @@ static int ext2_write_end(struct file *file, struct address_space *mapping,
 	return ret;
 }
 
-static int
-ext2_nobh_write_begin(struct file *file, struct address_space *mapping,
-		loff_t pos, unsigned len, struct page **pagep, void **fsdata)
-{
-	int ret;
-
-	ret = nobh_write_begin(mapping, pos, len, pagep, fsdata,
-			       ext2_get_block);
-	if (ret < 0)
-		ext2_write_failed(mapping, pos + len);
-	return ret;
-}
-
-static int ext2_nobh_writepage(struct page *page,
-			struct writeback_control *wbc)
-{
-	return nobh_writepage(page, ext2_get_block, wbc);
-}
-
 static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
 {
 	return generic_block_bmap(mapping,block,ext2_get_block);
@@ -978,21 +959,6 @@ const struct address_space_operations ext2_aops = {
 	.error_remove_page	= generic_error_remove_page,
 };
 
-const struct address_space_operations ext2_nobh_aops = {
-	.dirty_folio		= block_dirty_folio,
-	.invalidate_folio	= block_invalidate_folio,
-	.read_folio		= ext2_read_folio,
-	.readahead		= ext2_readahead,
-	.writepage		= ext2_nobh_writepage,
-	.write_begin		= ext2_nobh_write_begin,
-	.write_end		= nobh_write_end,
-	.bmap			= ext2_bmap,
-	.direct_IO		= ext2_direct_IO,
-	.writepages		= ext2_writepages,
-	.migrate_folio		= buffer_migrate_folio,
-	.error_remove_page	= generic_error_remove_page,
-};
-
 static const struct address_space_operations ext2_dax_aops = {
 	.writepages		= ext2_dax_writepages,
 	.direct_IO		= noop_direct_IO,
@@ -1298,13 +1264,10 @@ static int ext2_setsize(struct inode *inode, loff_t newsize)
 
 	inode_dio_wait(inode);
 
-	if (IS_DAX(inode)) {
+	if (IS_DAX(inode))
 		error = dax_zero_range(inode, newsize,
 				       PAGE_ALIGN(newsize) - newsize, NULL,
 				       &ext2_iomap_ops);
-	} else if (test_opt(inode->i_sb, NOBH))
-		error = nobh_truncate_page(inode->i_mapping,
-				newsize, ext2_get_block);
 	else
 		error = block_truncate_page(inode->i_mapping,
 				newsize, ext2_get_block);
@@ -1396,8 +1359,6 @@ void ext2_set_file_ops(struct inode *inode)
 	inode->i_fop = &ext2_file_operations;
 	if (IS_DAX(inode))
 		inode->i_mapping->a_ops = &ext2_dax_aops;
-	else if (test_opt(inode->i_sb, NOBH))
-		inode->i_mapping->a_ops = &ext2_nobh_aops;
 	else
 		inode->i_mapping->a_ops = &ext2_aops;
 }
@@ -1497,10 +1458,7 @@ struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
 	} else if (S_ISDIR(inode->i_mode)) {
 		inode->i_op = &ext2_dir_inode_operations;
 		inode->i_fop = &ext2_dir_operations;
-		if (test_opt(inode->i_sb, NOBH))
-			inode->i_mapping->a_ops = &ext2_nobh_aops;
-		else
-			inode->i_mapping->a_ops = &ext2_aops;
+		inode->i_mapping->a_ops = &ext2_aops;
 	} else if (S_ISLNK(inode->i_mode)) {
 		if (ext2_inode_is_fast_symlink(inode)) {
 			inode->i_link = (char *)ei->i_data;
@@ -1510,10 +1468,7 @@ struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
 		} else {
 			inode->i_op = &ext2_symlink_inode_operations;
 			inode_nohighmem(inode);
-			if (test_opt(inode->i_sb, NOBH))
-				inode->i_mapping->a_ops = &ext2_nobh_aops;
-			else
-				inode->i_mapping->a_ops = &ext2_aops;
+			inode->i_mapping->a_ops = &ext2_aops;
 		}
 	} else {
 		inode->i_op = &ext2_special_inode_operations;
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 5f6b7560eb3f3..5fd9a22d2b70c 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -178,10 +178,7 @@ static int ext2_symlink (struct user_namespace * mnt_userns, struct inode * dir,
 		/* slow symlink */
 		inode->i_op = &ext2_symlink_inode_operations;
 		inode_nohighmem(inode);
-		if (test_opt(inode->i_sb, NOBH))
-			inode->i_mapping->a_ops = &ext2_nobh_aops;
-		else
-			inode->i_mapping->a_ops = &ext2_aops;
+		inode->i_mapping->a_ops = &ext2_aops;
 		err = page_symlink(inode, symname, l);
 		if (err)
 			goto out_fail;
@@ -247,10 +244,7 @@ static int ext2_mkdir(struct user_namespace * mnt_userns,
 
 	inode->i_op = &ext2_dir_inode_operations;
 	inode->i_fop = &ext2_dir_operations;
-	if (test_opt(inode->i_sb, NOBH))
-		inode->i_mapping->a_ops = &ext2_nobh_aops;
-	else
-		inode->i_mapping->a_ops = &ext2_aops;
+	inode->i_mapping->a_ops = &ext2_aops;
 
 	inode_inc_link_count(inode);
 
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index f6a19f6d9f6d5..a1c1263c07ab3 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -296,9 +296,6 @@ static int ext2_show_options(struct seq_file *seq, struct dentry *root)
 		seq_puts(seq, ",noacl");
 #endif
 
-	if (test_opt(sb, NOBH))
-		seq_puts(seq, ",nobh");
-
 	if (test_opt(sb, USRQUOTA))
 		seq_puts(seq, ",usrquota");
 
@@ -551,7 +548,8 @@ static int parse_options(char *options, struct super_block *sb,
 			clear_opt (opts->s_mount_opt, OLDALLOC);
 			break;
 		case Opt_nobh:
-			set_opt (opts->s_mount_opt, NOBH);
+			ext2_msg(sb, KERN_INFO,
+				"nobh option not supported");
 			break;
 #ifdef CONFIG_EXT2_FS_XATTR
 		case Opt_user_xattr:
-- 
2.30.2

[PATCH 3/6] jfs: stop using the nobh helper

[Christoph Hellwig]

The nobh mode is an obscure feature to save lowlevel for large memory
32-bit configurations while trading for much slower performance and
has been long obsolete.  Switch to the regular buffer head based helpers
instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/jfs/inode.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/jfs/inode.c b/fs/jfs/inode.c
index 259326556ada6..d1ec920aa030a 100644
--- a/fs/jfs/inode.c
+++ b/fs/jfs/inode.c
@@ -301,13 +301,25 @@ static int jfs_write_begin(struct file *file, struct address_space *mapping,
 {
 	int ret;
 
-	ret = nobh_write_begin(mapping, pos, len, pagep, fsdata, jfs_get_block);
+	ret = block_write_begin(mapping, pos, len, pagep, jfs_get_block);
 	if (unlikely(ret))
 		jfs_write_failed(mapping, pos + len);
 
 	return ret;
 }
 
+static int jfs_write_end(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned copied, struct page *page,
+		void *fsdata)
+{
+	int ret;
+
+	ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
+	if (ret < len)
+		jfs_write_failed(mapping, pos + len);
+	return ret;
+}
+
 static sector_t jfs_bmap(struct address_space *mapping, sector_t block)
 {
 	return generic_block_bmap(mapping, block, jfs_get_block);
@@ -346,7 +358,7 @@ const struct address_space_operations jfs_aops = {
 	.writepage	= jfs_writepage,
 	.writepages	= jfs_writepages,
 	.write_begin	= jfs_write_begin,
-	.write_end	= nobh_write_end,
+	.write_end	= jfs_write_end,
 	.bmap		= jfs_bmap,
 	.direct_IO	= jfs_direct_IO,
 };
@@ -399,7 +411,7 @@ void jfs_truncate(struct inode *ip)
 {
 	jfs_info("jfs_truncate: size = 0x%lx", (ulong) ip->i_size);
 
-	nobh_truncate_page(ip->i_mapping, ip->i_size, jfs_get_block);
+	block_truncate_page(ip->i_mapping, ip->i_size, jfs_get_block);
 
 	IWRITE_LOCK(ip, RDWRLOCK_NORMAL);
 	jfs_truncate_nolock(ip, ip->i_size);
-- 
2.30.2

[PATCH 4/6] fs: remove the nobh helpers

[Christoph Hellwig]

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.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

[PATCH 5/6] fs: don't call ->writepage from __mpage_writepage

[Christoph Hellwig]

All callers of mpage_writepage use block_write_full_page as their
->writepage implementation when called from mpage_writepages
(although for ntfs3 this is obsfucated a bit).

Just call block_write_full_page directly instead of going through
the ->writepage indirection.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/mpage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index 31a97a0acf5f5..a354ef2b4b4eb 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -624,7 +624,7 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
 	/*
 	 * The caller has a ref on the inode, so *mapping is stable
 	 */
-	ret = mapping->a_ops->writepage(page, wbc);
+	ret = block_write_full_page(page, mpd->get_block, wbc);
 	mapping_set_error(mapping, ret);
 out:
 	mpd->bio = bio;
-- 
2.30.2

Re: [PATCH 5/6] fs: don't call ->writepage from __mpage_writepage

[Jan Kara]

On Mon 13-06-22 07:37:14, Christoph Hellwig wrote:
> All callers of mpage_writepage use block_write_full_page as their
> ->writepage implementation when called from mpage_writepages
> (although for ntfs3 this is obsfucated a bit).
> 
> Just call block_write_full_page directly instead of going through
> the ->writepage indirection.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Yeah, ntfs3 is not completely obvious but I agree we should not get to the
non-trivial case of ntfs_writepage() from mpage_writepages() now. Feel free
to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/mpage.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/mpage.c b/fs/mpage.c
> index 31a97a0acf5f5..a354ef2b4b4eb 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -624,7 +624,7 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
>  	/*
>  	 * The caller has a ref on the inode, so *mapping is stable
>  	 */
> -	ret = mapping->a_ops->writepage(page, wbc);
> +	ret = block_write_full_page(page, mpd->get_block, wbc);
>  	mapping_set_error(mapping, ret);
>  out:
>  	mpd->bio = bio;
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

[PATCH 6/6] fs: remove the NULL get_block case in mpage_writepages

[Christoph Hellwig]

No one calls mpage_writepages with a NULL get_block paramter, so remove
support for that case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/mpage.c | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index a354ef2b4b4eb..e4cf881634a6a 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -636,8 +636,6 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
  * @mapping: address space structure to write
  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
  * @get_block: the filesystem's block mapper function.
- *             If this is NULL then use a_ops->writepage.  Otherwise, go
- *             direct-to-BIO.
  *
  * This is a library function, which implements the writepages()
  * address_space_operation.
@@ -654,24 +652,16 @@ int
 mpage_writepages(struct address_space *mapping,
 		struct writeback_control *wbc, get_block_t get_block)
 {
+	struct mpage_data mpd = {
+		.get_block	= get_block,
+	};
 	struct blk_plug plug;
 	int ret;
 
 	blk_start_plug(&plug);
-
-	if (!get_block)
-		ret = generic_writepages(mapping, wbc);
-	else {
-		struct mpage_data mpd = {
-			.bio = NULL,
-			.last_block_in_bio = 0,
-			.get_block = get_block,
-		};
-
-		ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
-		if (mpd.bio)
-			mpage_bio_submit(mpd.bio);
-	}
+	ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
+	if (mpd.bio)
+		mpage_bio_submit(mpd.bio);
 	blk_finish_plug(&plug);
 	return ret;
 }
-- 
2.30.2

Re: [PATCH 6/6] fs: remove the NULL get_block case in mpage_writepages

[Jan Kara]

On Mon 13-06-22 07:37:15, Christoph Hellwig wrote:
> No one calls mpage_writepages with a NULL get_block paramter, so remove
> support for that case.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/mpage.c | 22 ++++++----------------
>  1 file changed, 6 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/mpage.c b/fs/mpage.c
> index a354ef2b4b4eb..e4cf881634a6a 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -636,8 +636,6 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
>   * @mapping: address space structure to write
>   * @wbc: subtract the number of written pages from *@wbc->nr_to_write
>   * @get_block: the filesystem's block mapper function.
> - *             If this is NULL then use a_ops->writepage.  Otherwise, go
> - *             direct-to-BIO.
>   *
>   * This is a library function, which implements the writepages()
>   * address_space_operation.
> @@ -654,24 +652,16 @@ int
>  mpage_writepages(struct address_space *mapping,
>  		struct writeback_control *wbc, get_block_t get_block)
>  {
> +	struct mpage_data mpd = {
> +		.get_block	= get_block,
> +	};
>  	struct blk_plug plug;
>  	int ret;
>  
>  	blk_start_plug(&plug);
> -
> -	if (!get_block)
> -		ret = generic_writepages(mapping, wbc);
> -	else {
> -		struct mpage_data mpd = {
> -			.bio = NULL,
> -			.last_block_in_bio = 0,
> -			.get_block = get_block,
> -		};
> -
> -		ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
> -		if (mpd.bio)
> -			mpage_bio_submit(mpd.bio);
> -	}
> +	ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
> +	if (mpd.bio)
> +		mpage_bio_submit(mpd.bio);
>  	blk_finish_plug(&plug);
>  	return ret;
>  }
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: remove the nobh helpers v2

[Matthew Wilcox]

On Mon, Jun 13, 2022 at 07:37:09AM +0200, Christoph Hellwig wrote:
> this series (against the pagecache for-next branch) removes the nobh
> helpers which are a variant of the "normal" buffer head helpers with
> special tradeoffs for machines with a lot of highmem, and thus rather
> obsolete.  They pass xfstests, or in case of jfs at least get as far
> as the baseline.

Thanks, applied & pushed out to the for-next branch.