On Mon, Feb 03, 2014 at 01:24:41AM +0000, shawn@xxxxxxxxxxxxxxx wrote:
> ---- Original Message ----
> From: "Andrey Wagin" <avagin@xxxxxxxxx>
> To: "Shawn Landden" <shawn@xxxxxxxxxxxxxxx>
> CC: "LKML" <linux-kernel@xxxxxxxxxxxxxxx>, "criu@xxxxxxxxxx"
> <criu@xxxxxxxxxx>, "Alexander Viro" <viro@xxxxxxxxxxxxxxxxxx>,
> linux-fsdevel@xxxxxxxxxxxxxxx, "Thomas Gleixner" <tglx@xxxxxxxxxxxxx>
> Sent: Wed, Dec 25, 2013, 12:46 AM
> Subject: Re: [CRIU] [PATCH] timerfd: show procfs fdinfo helper
>
>
> 2013/12/24 Shawn Landden <shawn@xxxxxxxxxxxxxxx>:
>
> | pos: 0
> | flags: 02004002
> | clockid: 0
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Shawn Landden <shawn@xxxxxxxxxxxxxxx>
> ---
> fs/timerfd.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/fs/timerfd.c b/fs/timerfd.c
> index 9293121..e5fa587 100644
> --- a/fs/timerfd.c
> +++ b/fs/timerfd.c
> @@ -25,6 +25,7 @@
> #include <linux/syscalls.h>
> #include <linux/compat.h>
> #include <linux/rcupdate.h>
> +#include <linux/seq_file.h>
>
> struct timerfd_ctx {
> union {
> @@ -284,7 +285,23 @@ static ssize_t timerfd_read(struct file *file,
> char __user *buf, size_t count,
> return res;
> }
>
> +#ifdef CONFIG_PROC_FS
> +static int timerfd_show_fdinfo(struct seq_file *m, struct file *f)
> +{
> + struct timerfd_ctx *ctx = f->private_data;
> + int clockid;
> +
> + clockid = ctx->clockid;
> + seq_printf(m, "clockid:\t%d\n", clockid);
>
>
>
> I think we can show ctx->ticks, itimerspec here. The ctx->ticks is
> required for proper dumping and restoring timerfd.
>
>
> How? Shouldn't the itemerspec (from timerfd_gettime and restored with
> timerfd_settime) and clockid be enough?
ctx->ticks is avaliable to userspace programs, so it must be restored,
otherwise you can break applications, which use this parameter in own
logic.
> How do we put the ctx->ticks back into
> the restored timerfd if we get it out with procfs?
read(2) returns ctx->ticks, so write() can be used for set it. It you
don't like this, you can add ioctl for setting ctx->ticks.
>
> +
> + return 0;
> +}
> +#endif
> +
> static const struct file_operations timerfd_fops = {
> +#ifdef CONFIG_PROC_FS
> + .show_fdinfo = timerfd_show_fdinfo,
> +#endif
> .release = timerfd_release,
> .poll = timerfd_poll,
> .read = timerfd_read,
> --
> 1.8.5.2.297.g3e57c29
>
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