linux-kernel - Re: [PATCH v2 18/36] fs: add ksys_write() helper; remove in-kernel calls to sys

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Date:   Fri, 16 Mar 2018 01:52:40 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Dominik Brodowski <linux@...inikbrodowski.net>
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        viro@...iv.linux.org.uk, luto@...nel.org, mingo@...nel.org,
        akpm@...ux-foundation.org, arnd@...db.de,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v2 18/36] fs: add ksys_write() helper; remove in-kernel
 calls to sys_write()

I really don't like this, as this is the wrong level of abstraction.

> diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
> index 79b7a3438d54..5a9cfde5fc28 100644
> --- a/arch/s390/kernel/compat_linux.c
> +++ b/arch/s390/kernel/compat_linux.c
> @@ -468,7 +468,7 @@ COMPAT_SYSCALL_DEFINE3(s390_write, unsigned int, fd, const char __user *, buf, c
>  	if ((compat_ssize_t) count < 0)
>  		return -EINVAL; 
>  
> -	return sys_write(fd, buf, count);
> +	return ksys_write(fd, buf, count);
>  }

This looks bogus to me.  Why does s390 have its own compat version of
write but not any of the other read and write familty calls?

> diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
> index 99e0b649fc0e..2d365c398ccc 100644
> --- a/init/do_mounts_rd.c
> +++ b/init/do_mounts_rd.c
> @@ -270,7 +270,7 @@ int __init rd_load_image(char *from)
>  			printk("Loading disk #%d... ", disk);
>  		}
>  		sys_read(in_fd, buf, BLOCK_SIZE);
> -		sys_write(out_fd, buf, BLOCK_SIZE);
> +		ksys_write(out_fd, buf, BLOCK_SIZE);
>  #if !defined(CONFIG_S390)
>  		if (!(i % 16)) {
>  			pr_cont("%c\b", rotator[rotate & 0x3]);

All the do_mounts / initramfs code should be rewritten to use filp_open
and vfs_read/vfs_write instead of adding hacks like this.