Re: [take2] Inotify: nested attributes support.

On Wed, 26 Nov 2008 11:29:36 +0300 Evgeniy Polyakov [off-list ref] wrote:

On Wed, Nov 26, 2008 at 12:15:38AM -0800, Andrew Morton (akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org) wrote:

quoted

OK, so we have a super-duper framework which will allow us to add pids
(and other things) to inotify messages.

Yup :)

quoted

This still doesn't provide a reason for anyone to be interested in the
code!  Why do we want pids in inotify messages?

 
I actually cared only about myself :)
I started the thread and implementation, because my application has to
differentiate IO made by itself and any IO made by system (another
users, crons, whatever else), inotify did not give me that info, so I
extended it. As of others: PID/TID may be used by watching applications
to reduce own load to not process own IO, things like beagle may show
who actually made changes into the file.

hrm.  Well this is the sort of information which reviewers want to know
all about before looking at an implementation.

quoted

And how does this work give that pids are (no longer) system-wide unique?

It gets pids from the caller's task_struct (via current), so its data is
as unique as process calling getpid() or syscall(__NR_gettid).

That means that the code delivers non-unique process identifiers to
userspace.  A client gets pid=42 but there are seven processes on the
machine with that pid.  Problem.


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