[cobalt-users] Re: find: /proc/5/fd: Permission denied (part 2)

[Bruce Timberlake <bruce@xxxxxxxxxx>]

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Found this after a little more Googling. The link is old, but seems to still 
be a relevant/plausible explanation:

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http://www.uwsg.iu.edu/hypermail/linux/kernel/9609.3/0296.html

Any number of number of opens for read and write are allowed; however, to
prevent confusion, if several processes are trying to control another
process, an exclusive open for write can be requested. An open for write
that includes the O_EXCL specifier only succeeds if the process is not
already open for a write, even if you are root or an otherwise privileged
user.

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So I'm guessing that whatever file descriptor -- and yes, that is what the 
"fd" stands for in this context! :) -- the mdrecoveryd process has open, it's 
open for exclusive write, meaning that even root can't get a peek at it.

Now I don't know if that's A Good Thing or not; someone with a lot more 
experience with RAID etc would have to comment and/or look at the code and 
see if it could be changed.

FYI, I'm using a non-RAID RaQ 4 (not even a 4i); in theory, the non-RAID 
machines [sh|c]ould have a non-RAID enabled kernel, and then the mdrecoveryd 
process wouldn't be an issue except on the 4r. But it *would* still be an 
issue on the 4r, so I guess it wouldn't hurt to check it out more...
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