Re: inotify_add_watch() returning ENOSPC in 2.6.24 [watch descriptor leak?]

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 5 Feb 2008 20:49:42 -0500 "Clem Taylor" <clem.taylor@gmail.com> wrote:

> I'm trying to move a MIPS based embedded system from 2.6.16.16 to
> 2.6.24. Most things seem to be working, but I'm having troubles with
> inotify. The code is using inotify to detect a file written to /tmp
> (tmpfs). The writer creates a file with a temporary name and then
> rename()s the tmp file over the file I'm monitoring.
> 
> With 2.6.16.16, everything works fine, but with 2.6.24, the inotify
> process runs for a while (~100 events) and then inotify_add_watch()
> returns ENOSPC. Once this happens, I can't add new watches, even if I
> kill the process and restart it. fs.inotify.max_user_instances and
> fs.inotify.max_user_watches are both 128, so I'd imagine I'm hitting
> this limit. For some reason the watches aren't getting cleaned up
> (even after the process is killed).
> 
> In a loop, the code is doing:
>     wd = inotify_add_watch(fd, file, IN_CLOSE_WRITE|IN_DELETE_SELF|IN_ONESHOT);
>     blocking read on notify fd
> 
> Has something changed in the inotify() API since 2.6.16.16, or could
> this be a leak?
> 

Good bug report, thanks.  That code was significantly altered in June 2006
and perhaps something broke.

It's a bit hard to find people who work on inotify, I'm afraid.  If you had
the time to come up with a script or program which demonstrates the bug,
that would be super-helpful?