linux-kernel - Re: [PATCH V2 4/9] fork: add option to not clone or dup files

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Message-ID: <20210922124634.zodjcbvksdkhjrym@wittgenstein>
Date:   Wed, 22 Sep 2021 14:46:34 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     hdanton@...a.com, hch@...radead.org, stefanha@...hat.com,
        jasowang@...hat.com, mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, axboe@...nel.dk,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 4/9] fork: add option to not clone or dup files

On Tue, Sep 21, 2021 at 04:52:13PM -0500, Mike Christie wrote:
> Each vhost device gets a thread that is used to perform IO and management
> operations. Instead of a thread that is accessing a device, the thread is
> part of the device, so when it calls the kernel_worker() function added in
> the next patch we can't dup or clone the parent's files/FDS because it would
> do an extra increment on ourself.
> 
> Later, when we do:
> 
> Qemu process exits:
>         do_exit -> exit_files -> put_files_struct -> close_files
> 
> we would leak the device's resources because of that extra refcount
> on the fd or file_struct.
> 
> This patch adds a no_files option so these worker threads can prevent
> taking an extra refcount on themselves.
> 
> Signed-off-by: Mike Christie <michael.christie@...cle.com>

Ok,
Acked-by: Christian Brauner <christian.brauner@...ntu.com>