From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Cyrill Gorcunov <gorcunov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
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jbaron-JqFfY2XvxFXQT0dZR+AlfA@public.gmane.org,
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Subject: Re: [patch v4 resend 2/2] kcmp: Add KCMP_EPOLL_TFD mode to compare epoll target files
Date: Fri, 12 May 2017 15:00:18 -0700 [thread overview]
Message-ID: <20170512150018.b931c7f5295dd7484845fcec@linux-foundation.org> (raw)
In-Reply-To: <20170424154423.511592110-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
On Mon, 24 Apr 2017 18:39:28 +0300 Cyrill Gorcunov <gorcunov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> With current epoll architecture target files are addressed
> with file_struct and file descriptor number, where the last
> is not unique. Moreover files can be transferred from another
> process via unix socket, added into queue and closed then
> so we won't find this descriptor in the task fdinfo list.
>
> Thus to checkpoint and restore such processes CRIU needs to
> find out where exactly the target file is present to add it into
> epoll queue. For this sake one can use kcmp call where
> some particular target file from the queue is compared with
> arbitrary file passed as an argument.
>
> Because epoll target files can have same file descriptor
> number but different file_struct a caller should explicitly
> specify the offset within.
>
> To test if some particular file is matching entry inside
> epoll one have to
>
> - fill kcmp_epoll_slot structure with epoll file descriptor,
> target file number and target file offset (in case if only
> one target is present then it should be 0)
>
> - call kcmp as kcmp(pid1, pid2, KCMP_EPOLL_TFD, fd, &kcmp_epoll_slot)
> - the kernel fetch file pointer matching file descriptor @fd of pid1
> - lookups for file struct in epoll queue of pid2 and returns traditional
> 0,1,2 result for sorting purpose
That's quite a bit more code. Is there a neat way of making it depend
on a new CONFIG_foo, then select CONFIG_foo if
CONFIG_CHECKPOINT_RESTORE?
next prev parent reply other threads:[~2017-05-12 22:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-24 15:39 [patch v4 resend 2/2] kcmp: Add KCMP_EPOLL_TFD mode to compare epoll target files Cyrill Gorcunov
[not found] ` <20170424154423.511592110-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-05-12 22:00 ` Andrew Morton [this message]
[not found] ` <20170512150018.b931c7f5295dd7484845fcec-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2017-05-12 22:14 ` Cyrill Gorcunov
2017-05-12 22:41 ` Jann Horn
2017-05-12 22:53 ` Cyrill Gorcunov
[not found] ` <20170512225340.GD1881-ZmlpmtaulQd+urZeOPWqwQ@public.gmane.org>
2017-05-13 1:45 ` Andrei Vagin
[not found] ` <20170513014508.GA21900-1ViLX0X+lBJGNQ1M2rI3KwRV3xvJKrda@public.gmane.org>
2017-05-13 6:55 ` Cyrill Gorcunov
[not found] ` <20170513065514.GE1881-ZmlpmtaulQd+urZeOPWqwQ@public.gmane.org>
2017-05-13 7:15 ` Cyrill Gorcunov
2017-09-17 16:01 ` [v4,resend,2/2] " Eugene Syromiatnikov
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