Re: [RFC PATCH v1 10/18] xfs: Enable async write file modification handling.

[Dave Chinner <david@fromorbit.com>]

On Tue, Apr 26, 2022 at 10:43:27AM -0700, Stefan Roesch wrote:
> This modifies xfs write checks to return -EAGAIN if the request either
> requires to remove privileges or needs to update the file modification
> time. This is required for async buffered writes, so the request gets
> handled in the io worker.
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/xfs/xfs_file.c | 39 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 5bddb1e9e0b3..6f9da1059e8b 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -299,6 +299,43 @@ xfs_file_read_iter(
>  	return ret;
>  }
>  
> +static int xfs_file_modified(struct file *file, int flags)
> +{
> +	int ret;
> +	struct dentry *dentry = file_dentry(file);
> +	struct inode *inode = file_inode(file);
> +	struct timespec64 now = current_time(inode);
> +
> +	/*
> +	 * Clear the security bits if the process is not being run by root.
> +	 * This keeps people from modifying setuid and setgid binaries.
> +	 */
> +	ret = need_file_remove_privs(inode, dentry);
> +	if (ret < 0) {
> +		return ret;
> +	} else if (ret > 0) {
> +		if (flags & IOCB_NOWAIT)
> +			return -EAGAIN;
> +
> +		ret = do_file_remove_privs(file, inode, dentry, ret);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = need_file_update_time(inode, file, &now);
> +	if (ret <= 0)
> +		return ret;
> +	if (flags & IOCB_NOWAIT) {
> +		if (IS_PENDING_TIME(inode))
> +			return 0;
> +
> +		inode->i_flags |= S_PENDING_TIME;
> +		return -EAGAIN;
> +	}
> +
> +	return do_file_update_time(inode, file, &now, ret);
> +}

This has nothing XFS specific in it. It belongs in the VFS code.

-Dave.

-- 
Dave Chinner
david@fromorbit.com