linux-kernel - Re: [take2] Inotify: nested attributes support.

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Message-ID: <20081204090900.GA4615@ioremap.net>
Date:	Thu, 4 Dec 2008 12:09:00 +0300
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Pavel Machek <pavel@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, john@...nmccutchan.com,
	arnd@...db.de, mtk.manpages@...il.com, hch@....de, rlove@...ve.org,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	davidn@...idnewall.com, Eric Paris <eparis@...hat.com>
Subject: Re: [take2] Inotify: nested attributes support.

On Thu, Dec 04, 2008 at 09:43:10AM +0100, Pavel Machek (pavel@...e.cz) wrote:
> Actually, does the kernel even know who initiated the i/o?
> 
> Take two threads, both mapping /etc/something , both of them writing
> through the mmap. Kernel sees dirty pages so it writes them back, but
> which thread is repsonsible for the write?

It depends. If write will be done with write() syscall, caller will be
stored. Otherwise inotify does not hook into page fault code afaics.

> > > 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).
> 
> What happens on mmap()?

mmap() syscall is not processed by inotify.

-- 
	Evgeniy Polyakov
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