On Wed, 02.05.12 07:45, Stef Bon (stef...@gmail.com) wrote:
> Hi,
>
> I've been looking into the code how systemd handles the automounting.
Heya,
> I've got two issues:
>
> a. I've found the handling of the "missing" packet
> (autofs_ptype_missing_direct), which triggers the
> mounting. But I did not found the handling of the expire packet
> (autofs_ptype_expire_direct). Is this on purpose?
> I see a timeout set, so I guess it was the intention to handle the
> expire.
We currently don't do expiration, since this wasn't intended as a full
autofs implementation, but just a way to parallelize and delay load
things at boot.
That said, we could support expire easily I guess, and so I have now
added this to the TODO list.
> b. the packet read from the pipe is of type union
> autofs_v5_packet_union which looks like:
>
> union autofs_v5_packet_union {
> struct autofs_packet_hdr hdr;
> struct autofs_v5_packet v5_packet;
> autofs_packet_missing_indirect_t missing_indirect;
> autofs_packet_expire_indirect_t expire_indirect;
> autofs_packet_missing_direct_t missing_direct;
> autofs_packet_expire_direct_t expire_direct;
> };
>
> where autofs_v5_packet is:
>
> struct autofs_v5_packet {
> struct autofs_packet_hdr hdr;
> autofs_wqt_t wait_queue_token;
> __u32 dev;
> __u64 ino;
> __u32 uid;
> __u32 gid;
> __u32 pid;
> __u32 tgid;
> __u32 len;
> char name[NAME_MAX+1];
> };
>
> now in the code of automount_fd_event, the selection is based upon
> packet.hdr.type, and futher the fields
> packet.v5_packet.pid are used. Now this while packet is an union: it's
> used as hdr OR as autofs_v5_packet, not both at the same time.
> It works, so here probably happens something strange: while using the
> field packet.hdr, actually the field packet.v5_packet.hdr is used. Is
> this correct?
In Autofs5 all packets have the same format which exposes
pid. i.e. autofs_packet_xxx_yyy_t are all typedef'ed to the same packet
struct. Hence accessing this this way is safe.
Lennart
--
Lennart Poettering - Red Hat, Inc.
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