linux-ext4 - Re: [PATCH 01/19] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags

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Message-ID: <20171013071203.GA9105@infradead.org>
Date:   Fri, 13 Oct 2017 00:12:03 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Ted Tso <tytso@....edu>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 01/19] mm: introduce MAP_SHARED_VALIDATE, a mechanism to
 safely define new mmap flags

So did we settle on the new mmap_validate vs adding a new argument
to ->mmap for real now?  I have to say I'd much prefer passing an
additional argument instead, but if higher powers rule that out
this version is ok.

> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 13dab191a23e..5aee97d64cae 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1701,6 +1701,8 @@ struct file_operations {
>  	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
>  	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
>  	int (*mmap) (struct file *, struct vm_area_struct *);
> +	int (*mmap_validate) (struct file *, struct vm_area_struct *,
> +			unsigned long);

Can we make this return a bool for ok vs not ok?  That way we only
need to have the error code discussion in one place instead of every
file system.