linux-kernel - Re: [BUG] Using inotify on /proc/partitoins

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Message-ID: <20130614020523.GL4165@ZenIV.linux.org.uk>
Date:	Fri, 14 Jun 2013 03:05:23 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	majianpeng <majianpeng@...il.com>
Cc:	john <john@...nmccutchan.com>, rlove <rlove@...ve.org>,
	eparis <eparis@...isplace.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Using inotify on /proc/partitoins

On Fri, Jun 14, 2013 at 09:26:49AM +0800, majianpeng wrote:
> Hi all,
>      I wanted to monitor /proc/partitions using inotify.


That, indeed, is a bug.  Easily fixed - don't do that.

> But when i call 'cat /proc/partitions',the program can't return.
> So i added some message in kernel in order to find the reason.
> In procfs for some files, the inode used this method to alloc.
> proc_lookup-->proc_lookup_de--->proc_get_inode-->new_inode_pseudo
> In new_inode_pseudo, it will alloc new inode so every open-operation procfs will alloc new inode.
> So inotify can't work.

Of course, it can't work.  Inotify if a kludge that kinda-sorta works
for local disk-backed filesystems, if you do not mind a pile of races.
For anything else it's completely worthless.
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