linux-kernel - Re: [RFC PATCH 16/35] ovl: readd lsattr/chattr support

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Date:   Mon, 23 Apr 2018 11:41:19 +0530
From:   Ritesh Harjani <riteshh@...eaurora.org>
To:     Miklos Szeredi <mszeredi@...hat.com>, linux-unionfs@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 16/35] ovl: readd lsattr/chattr support



On 4/12/2018 8:38 PM, Miklos Szeredi wrote:
> Implement FS_IOC_GETFLAGS and FS_IOC_SETFLAGS.
> 
> Needs vfs_ioctl() exported to modules.
Do you think if it is better to separate out ovl implementation and 
export of vfs_ioctl method ?
Probably there are other users which should be using vfs_ioctl method as 
well (like ecryptfs) ?

> 
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
>   fs/internal.h       |  1 -
>   fs/ioctl.c          |  1 +
>   fs/overlayfs/file.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/fs.h  |  2 ++
>   4 files changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/internal.h b/fs/internal.h
> index 3319bf39e339..d5108d9c6a2f 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -176,7 +176,6 @@ extern const struct dentry_operations ns_dentry_operations;
>    */
>   extern int do_vfs_ioctl(struct file *file, unsigned int fd, unsigned int cmd,
>   		    unsigned long arg);
> -extern long vfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
>   
>   /*
>    * iomap support:
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 5ace7efb0d04..696f4c46a868 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -49,6 +49,7 @@ long vfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>    out:
>   	return error;
>   }
> +EXPORT_SYMBOL(vfs_ioctl);
>   
>   static int ioctl_fibmap(struct file *filp, int __user *p)
>   {
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 05e3e2f80b89..cc004ff1b05b 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -8,6 +8,7 @@
>   
>   #include <linux/cred.h>
>   #include <linux/file.h>
> +#include <linux/mount.h>
>   #include <linux/xattr.h>
>   #include <linux/uio.h>
>   #include "overlayfs.h"
> @@ -291,6 +292,63 @@ long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>   	return ret;
>   }
>   
> +static long ovl_real_ioctl(struct file *file, unsigned int cmd,
> +			   unsigned long arg)
> +{
> +	struct fd real;
> +	const struct cred *old_cred;
> +	long ret;
> +
> +	ret = ovl_real_file(file, &real);
> +	if (ret)
> +		return ret;
> +
> +	old_cred = ovl_override_creds(file_inode(file)->i_sb);
> +	ret = vfs_ioctl(real.file, cmd, arg);
> +	revert_creds(old_cred);
> +
> +	fdput(real);
> +
> +	return ret;
> +}
> +
> +long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +	long ret;
> +	struct inode *inode = file_inode(file);
> +
> +	switch (cmd) {
> +	case FS_IOC_GETFLAGS:
> +		ret = ovl_real_ioctl(file, cmd, arg);
> +		break;
> +
> +	case FS_IOC_SETFLAGS:
> +		if (!inode_owner_or_capable(inode))
> +			return -EACCES;
> +
> +		ret = mnt_want_write_file(file);
> +		if (ret)
> +			return ret;
> +
> +		ret = ovl_copy_up(file_dentry(file));
> +		if (!ret) {
> +			ret = ovl_real_ioctl(file, cmd, arg);
> +
> +			inode_lock(inode);
> +			ovl_copyflags(ovl_inode_real(inode), inode);
> +			inode_unlock(inode);
> +		}
> +
> +		mnt_drop_write_file(file);
> +		break;
> +
> +	default:
> +		ret = -ENOTTY;
> +	}
> +
> +	return ret;
> +}
> +
>   const struct file_operations ovl_file_operations = {
>   	.open		= ovl_open,
>   	.release	= ovl_release,
> @@ -300,4 +358,5 @@ const struct file_operations ovl_file_operations = {
>   	.fsync		= ovl_fsync,
>   	.mmap		= ovl_mmap,
>   	.fallocate	= ovl_fallocate,
> +	.unlocked_ioctl	= ovl_ioctl,

What about compat_ioctl ? should that implementation also go in the same 
patch ?

>   };
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 0b215faa30ae..1add10f04b56 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1621,6 +1621,8 @@ int vfs_mkobj(struct dentry *, umode_t,
>   		int (*f)(struct dentry *, umode_t, void *),
>   		void *);
>   
> +extern long vfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
> +
>   /*
>    * VFS file helper functions.
>    */
> 

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