From: David Howells <dhowells@redhat.com>
To: Derrick J Brashear <shadow@dementia.org>
cc: openafs-devel@openafs.org, linux-kernel@vger.kernel.org
Subject: Adding an "acceptable" interface to the Linux kernel for AFS
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Date: Fri, 09 May 2003 11:16:49 +0100
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Hi,

I'm trying to write an AFS syscall framework for the Linux kernel that can do
two things:

 (1) Handle PAGs without the need to subvert the groups list and override the
     set/getgroups syscalls.

 (2) Cache authentication data per PAG, doing garbage collection automatically
     when a PAG no longer has any attached processes.

 (3) Pass other AFS syscall operations to interfaces in whatever AFS
     filesystem module is currently loaded (OpenAFS, Arla, etc.).

However, (3) is somewhat tricky as the interface isn't very consistent. For
instance, it would appear that all PIOCTL commands should require a path, but
some of them don't:-/ I don't know why these commands were made PIOCTLs rather
than using the CALL interface, but it makes multiplexing in the core kernel
more difficult.

I'm wondering how attached OpenAFS is to this interface? Can OpenAFS be
altered to use the following access points instead:

 (1) setpag(pag_t pag)

 (2) getpag()

 (3) settok(const char *fs, const char *domain, size_t size, const void *data)

 (4) gettok(const char *fs, const char *domain, size_t size, void *data)

 (5) deltok(const char *fs, const char *domain)

 (6) cleartoks(const char *fs)

 (7) pioctl(const char *path, int cmd, void *arg, int followsymlinks)

     (Where path is mandatory.)

     It may be possible to replace this entirely with calls to setxattr and
     co. from userspace... apart from VIOC_AFS_STAT_MT_PT that is, and that
     could be done with open/ioctl/close on the directory.

 (8) fsctl(const char *fs, const char *cmd, struct fsctl_buf)

     Using:

	struct fsctl_buf { size_t in_size, out_size; void *in, *out; };

     All miscellaneous ops would be done through this. It would work
     internally as nfsservctl does in 2.5.

David
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