From: Jerome Glisse <jglisse@redhat.com>
To: Jeff Layton <jlayton@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Dave Chinner <david@fromorbit.com>,
linux-mm@kvack.org, lsf-pc@lists.linux-foundation.org,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-block@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [LSF/MM] schedule suggestion
Date: Thu, 19 Apr 2018 13:26:10 -0400 [thread overview]
Message-ID: <20180419172609.GD3519@redhat.com> (raw)
In-Reply-To: <1524157119.2943.6.camel@kernel.org>
On Thu, Apr 19, 2018 at 12:58:39PM -0400, Jeff Layton wrote:
> On Thu, 2018-04-19 at 12:30 -0400, Jerome Glisse wrote:
> > On Thu, Apr 19, 2018 at 07:43:56AM -0700, Matthew Wilcox wrote:
> > > On Thu, Apr 19, 2018 at 10:38:25AM -0400, Jerome Glisse wrote:
> > > > Oh can i get one more small slot for fs ? I want to ask if they are
> > > > any people against having a callback everytime a struct file is added
> > > > to a task_struct and also having a secondary array so that special
> > > > file like device file can store something opaque per task_struct per
> > > > struct file.
> > >
> > > Do you really want something per _thread_, and not per _mm_?
> >
> > Well per mm would be fine but i do not see how to make that happen with
> > reasonable structure. So issue is that you can have multiple task with
> > same mm but different file descriptors (or am i wrong here ?) thus there
> > would be no easy way given a struct file to lookup the per mm struct.
> >
> > So as a not perfect solution i see a new array in filedes which would
> > allow device driver to store a pointer to their per mm data structure.
> > To be fair usualy you will only have a single fd in a single task for
> > a given device.
> >
> > If you see an easy way to get a per mm per inode pointer store somewhere
> > with easy lookup i am all ears :)
> >
>
> I may be misunderstanding, but to be clear: struct files don't get
> added to a thread, per-se.
>
> When userland calls open() or similar, the struct file gets added to
> the files_struct. Those are generally shared with other threads within
> the same process. The files_struct can also be shared with other
> processes if you clone() with the right flags.
>
> Doing something per-thread on every open may be rather difficult to do.
Basicly i want a callback in __fd_install(), do_dup2(), dup_fd() and
add void * *private_data; to struct fdtable (also a default array to
struct files_struct). The callback would be part of struct file_operations.
and only call if it exist (os overhead is only for device driver that
care).
Did i miss something fundamental ? copy_files() call dup_fd() so i
should be all set here.
I will work on patches i was hoping this would not be too much work.
Cheers,
J�r�me
next prev parent reply other threads:[~2018-04-19 17:26 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-18 21:19 [LSF/MM] schedule suggestion Jerome Glisse
2018-04-19 0:48 ` Dave Chinner
2018-04-19 1:55 ` Dave Chinner
2018-04-19 14:38 ` Jerome Glisse
2018-04-19 14:43 ` Matthew Wilcox
2018-04-19 16:30 ` Jerome Glisse
2018-04-19 16:58 ` Jeff Layton
2018-04-19 17:26 ` Jerome Glisse [this message]
2018-04-19 18:31 ` Jeff Layton
2018-04-19 19:31 ` Jerome Glisse
2018-04-19 19:56 ` Matthew Wilcox
2018-04-19 20:15 ` Jerome Glisse
2018-04-19 20:25 ` Matthew Wilcox
2018-04-19 20:39 ` Al Viro
2018-04-19 21:08 ` Jerome Glisse
2018-04-19 20:51 ` Al Viro
2018-04-19 20:33 ` Al Viro
2018-04-19 20:58 ` Jerome Glisse
2018-04-19 21:21 ` Al Viro
2018-04-19 21:47 ` Jerome Glisse
2018-04-19 22:13 ` Al Viro
2018-04-19 14:51 ` Chris Mason
2018-04-19 15:07 ` Martin K. Petersen
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