ext2: remove nobh support

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>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

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).
 

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 */

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;

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);
 

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: