linux-ext4 - Re: [PATCH 02/17] fs: remove the special !CONFIG_BLOCK def_blk

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Date:   Mon, 24 Apr 2023 12:22:30 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>
Cc:     Miklos Szeredi <miklos@...redi.hu>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        ceph-devel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-xfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/17] fs: remove the special !CONFIG_BLOCK def_blk_fops

Hi,

On 4/23/23 22:49, Christoph Hellwig wrote:
> def_blk_fops always returns -ENODEV, which dosn't match the return value
> of a non-existing block device with CONFIG_BLOCK, which is -ENXIO.
> Just remove the extra implementation and fall back to the default
> no_open_fops that always returns -ENXIO.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/Makefile   | 10 ++--------
>  fs/inode.c    |  3 ++-
>  fs/no-block.c | 19 -------------------
>  3 files changed, 4 insertions(+), 28 deletions(-)
>  delete mode 100644 fs/no-block.c
> 
> diff --git a/fs/Makefile b/fs/Makefile
> index 05f89b5c962f88..da21e7d0a1cf37 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -18,14 +18,8 @@ obj-y :=	open.o read_write.o file_table.o super.o \
>  		fs_types.o fs_context.o fs_parser.o fsopen.o init.o \
>  		kernel_read_file.o mnt_idmapping.o remap_range.o
>  
> -ifeq ($(CONFIG_BLOCK),y)
> -obj-y +=	buffer.o mpage.o
> -else
> -obj-y +=	no-block.o
> -endif
> -
> -obj-$(CONFIG_PROC_FS) += proc_namespace.o
> -
> +obj-$(CONFIG_BLOCK)		+= buffer.o mpage.o
> +obj-$(CONFIG_PROC_FS)		+= proc_namespace.o
>  obj-$(CONFIG_LEGACY_DIRECT_IO)	+= direct-io.o
>  obj-y				+= notify/
>  obj-$(CONFIG_EPOLL)		+= eventpoll.o
> diff --git a/fs/inode.c b/fs/inode.c
> index 4558dc2f135573..d43f07f146eb73 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -2265,7 +2265,8 @@ void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
>  		inode->i_fop = &def_chr_fops;
>  		inode->i_rdev = rdev;
>  	} else if (S_ISBLK(mode)) {
> -		inode->i_fop = &def_blk_fops;
> +		if (IS_ENABLED(CONFIG_BLOCK))
> +			inode->i_fop = &def_blk_fops;

It looks like def_blk_fops is being removed (commit message and patch
fragment below), but here (above line) it is being used.

Am I just confused?

>  		inode->i_rdev = rdev;
>  	} else if (S_ISFIFO(mode))
>  		inode->i_fop = &pipefifo_fops;
> diff --git a/fs/no-block.c b/fs/no-block.c
> deleted file mode 100644
> index 481c0f0ab4bd2c..00000000000000
> --- a/fs/no-block.c
> +++ /dev/null
> @@ -1,19 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-or-later
> -/* no-block.c: implementation of routines required for non-BLOCK configuration
> - *
> - * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
> - * Written by David Howells (dhowells@...hat.com)
> - */
> -
> -#include <linux/kernel.h>
> -#include <linux/fs.h>
> -
> -static int no_blkdev_open(struct inode * inode, struct file * filp)
> -{
> -	return -ENODEV;
> -}
> -
> -const struct file_operations def_blk_fops = {
> -	.open		= no_blkdev_open,
> -	.llseek		= noop_llseek,
> -};

-- 
~Randy