Re: [RFC] O_NOACC: open without any access

[Miklos Szeredi]

On Tue, 23 Jun 2009, David Howells wrote:
> Reference count on which module?  This would not take a reference on
> the device driver as it would not refer to it, but would still have
> a file struct, an inode struct and a dentry struct on the underlying
> fs.

So how about the following: provide a new open flag O_FILESYSTEM,
meaning it opens the file on the underlying filesystem instead of the
device/socket/symlink/etc...

Add a new inode->i_filesystem_fop pointer which is used instead of
inode->i_fop in case if O_FILESYSTEM.  If ->i_filesystem_fop isn't set
by the filesystem, fall back to a default which returns -EBADF for all
operations (except open).

Define O_NOACC as 3.  On open(..., O_FILESYSTEM | O_NOACC) require no
privileges on the file.

AFS would set up i_filesystem_fop with its ->ioctl() function. No
special handling needed for revoke()...

That would work, no?

Thanks,
Miklos

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