[patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v2

[patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v2

[Cyrill Gorcunov]

Hi, here is an updated series, changes mostly in show_fdinfo code which now
produces a way more information (and documentation update). Please take a look
once time permit. Thanks!

[patch 1/3] timerfd: Implement show_fdinfo method

[Cyrill Gorcunov]

[-- Attachment #1: timerfd-show-fdinfo-3 --]
[-- Type: text/plain, Size: 2974 bytes --]

For checkpoint/restore of timerfd files we need to know how exactly
the timer were armed to be able to handle it. Thus implement show_fdinfo
method which provides enough information for timer re-creation.

One of significant changes I think is addition of
timerfd_ctx::settime_flags member. Currently there are
two flags TFD_TIMER_ABSTIME and TFD_TIMER_CANCEL_ON_SET,
and the second can be found from @might_cancel variable
but in case if the flags will be extended in future we
most probably will have to somehow remember them explicitly
anyway so I guss doing that right now won't hurt.

To not bloat the timerfd_ctx structure I've converted
@expired to short integer and defined @settime_flags
as short as well.

v2 (by avagin@, vdavydov@ and tglx@):

 - Add it_value/it_interval fields
 - Save flags being used in timerfd_setup in context

CC: Shawn Landden <shawn@churchofgit.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <avagin@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 fs/timerfd.c |   30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

Index: linux-2.6.git/fs/timerfd.c
===================================================================
--- linux-2.6.git.orig/fs/timerfd.c
+++ linux-2.6.git/fs/timerfd.c
@@ -35,8 +35,9 @@ struct timerfd_ctx {
 	ktime_t moffs;
 	wait_queue_head_t wqh;
 	u64 ticks;
-	int expired;
 	int clockid;
+	short unsigned expired;
+	short unsigned settime_flags;	/* to show in fdinfo */
 	struct rcu_head rcu;
 	struct list_head clist;
 	bool might_cancel;
@@ -196,6 +197,8 @@ static int timerfd_setup(struct timerfd_
 		if (timerfd_canceled(ctx))
 			return -ECANCELED;
 	}
+
+	ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
 	return 0;
 }
 
@@ -284,11 +287,36 @@ static ssize_t timerfd_read(struct file
 	return res;
 }
 
+static int timerfd_show(struct seq_file *m, struct file *file)
+{
+	struct timerfd_ctx *ctx = file->private_data;
+	struct itimerspec t;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
+	t.it_interval = ktime_to_timespec(ctx->tintv);
+	spin_unlock_irq(&ctx->wqh.lock);
+
+	return seq_printf(m,
+			  "clockid: %d\n"
+			  "ticks: %llu\n"
+			  "settime flags: 0%o\n"
+			  "it_value: (%llu, %llu)\n"
+			  "it_interval: (%llu, %llu)\n",
+			  ctx->clockid, (unsigned long long)ctx->ticks,
+			  ctx->settime_flags,
+			  (unsigned long long)t.it_value.tv_sec,
+			  (unsigned long long)t.it_value.tv_nsec,
+			  (unsigned long long)t.it_interval.tv_sec,
+			  (unsigned long long)t.it_interval.tv_nsec);
+}
+
 static const struct file_operations timerfd_fops = {
 	.release	= timerfd_release,
 	.poll		= timerfd_poll,
 	.read		= timerfd_read,
 	.llseek		= noop_llseek,
+	.show_fdinfo	= timerfd_show,
 };
 
 static int timerfd_fget(int fd, struct fd *p)

Re: [patch 1/3] timerfd: Implement show_fdinfo method

[Vladimir Davydov]

Hi Cyrill,

On 04/07/2014 09:47 PM, Cyrill Gorcunov wrote:
> For checkpoint/restore of timerfd files we need to know how exactly
> the timer were armed to be able to handle it. Thus implement show_fdinfo
> method which provides enough information for timer re-creation.
>
> One of significant changes I think is addition of
> timerfd_ctx::settime_flags member. Currently there are
> two flags TFD_TIMER_ABSTIME and TFD_TIMER_CANCEL_ON_SET,
> and the second can be found from @might_cancel variable
> but in case if the flags will be extended in future we
> most probably will have to somehow remember them explicitly
> anyway so I guss doing that right now won't hurt.
>
> To not bloat the timerfd_ctx structure I've converted
> @expired to short integer and defined @settime_flags
> as short as well.
>
> v2 (by avagin@, vdavydov@ and tglx@):
>
>  - Add it_value/it_interval fields
>  - Save flags being used in timerfd_setup in context
>
> CC: Shawn Landden <shawn@churchofgit.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Andrey Vagin <avagin@openvz.org>
> CC: Pavel Emelyanov <xemul@parallels.com>
> CC: Vladimir Davydov <vdavydov@parallels.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> ---
>  fs/timerfd.c |   30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.git/fs/timerfd.c
> ===================================================================
> --- linux-2.6.git.orig/fs/timerfd.c
> +++ linux-2.6.git/fs/timerfd.c
> @@ -35,8 +35,9 @@ struct timerfd_ctx {
>  	ktime_t moffs;
>  	wait_queue_head_t wqh;
>  	u64 ticks;
> -	int expired;
>  	int clockid;
> +	short unsigned expired;
> +	short unsigned settime_flags;	/* to show in fdinfo */
>  	struct rcu_head rcu;
>  	struct list_head clist;
>  	bool might_cancel;
> @@ -196,6 +197,8 @@ static int timerfd_setup(struct timerfd_
>  		if (timerfd_canceled(ctx))
>  			return -ECANCELED;
>  	}
> +
> +	ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
>  	return 0;
>  }
>  
> @@ -284,11 +287,36 @@ static ssize_t timerfd_read(struct file
>  	return res;
>  }
>  
> +static int timerfd_show(struct seq_file *m, struct file *file)
> +{
> +	struct timerfd_ctx *ctx = file->private_data;
> +	struct itimerspec t;
> +
> +	spin_lock_irq(&ctx->wqh.lock);
> +	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
> +	t.it_interval = ktime_to_timespec(ctx->tintv);
> +	spin_unlock_irq(&ctx->wqh.lock);
> +
> +	return seq_printf(m,
> +			  "clockid: %d\n"
> +			  "ticks: %llu\n"
> +			  "settime flags: 0%o\n"
> +			  "it_value: (%llu, %llu)\n"
> +			  "it_interval: (%llu, %llu)\n",

IMO, one would expect to setup the timer on restore by passing the
values of settime_flags, it_value, and it_interval obtained from the
fdinfo to sys_timerfd_settime, but this will be incorrect, because AFAIU
the it_value you report here is always relative to the current time, no
matter whether TFD_TIMER_ABSTIME was set in settime_flags or not. Is it OK?

Thanks.

> +			  ctx->clockid, (unsigned long long)ctx->ticks,
> +			  ctx->settime_flags,
> +			  (unsigned long long)t.it_value.tv_sec,
> +			  (unsigned long long)t.it_value.tv_nsec,
> +			  (unsigned long long)t.it_interval.tv_sec,
> +			  (unsigned long long)t.it_interval.tv_nsec);
> +}
> +
>  static const struct file_operations timerfd_fops = {
>  	.release	= timerfd_release,
>  	.poll		= timerfd_poll,
>  	.read		= timerfd_read,
>  	.llseek		= noop_llseek,
> +	.show_fdinfo	= timerfd_show,
>  };
>  
>  static int timerfd_fget(int fd, struct fd *p)

Re: [patch 1/3] timerfd: Implement show_fdinfo method

[Cyrill Gorcunov]

On Tue, Apr 08, 2014 at 10:17:14AM +0400, Vladimir Davydov wrote:
...
> > +static int timerfd_show(struct seq_file *m, struct file *file)
> > +{
> > +	struct timerfd_ctx *ctx = file->private_data;
> > +	struct itimerspec t;
> > +
> > +	spin_lock_irq(&ctx->wqh.lock);
> > +	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
> > +	t.it_interval = ktime_to_timespec(ctx->tintv);
> > +	spin_unlock_irq(&ctx->wqh.lock);
> > +
> > +	return seq_printf(m,
> > +			  "clockid: %d\n"
> > +			  "ticks: %llu\n"
> > +			  "settime flags: 0%o\n"
> > +			  "it_value: (%llu, %llu)\n"
> > +			  "it_interval: (%llu, %llu)\n",
> 
> IMO, one would expect to setup the timer on restore by passing the
> values of settime_flags, it_value, and it_interval obtained from the
> fdinfo to sys_timerfd_settime, but this will be incorrect, because AFAIU
> the it_value you report here is always relative to the current time, no
> matter whether TFD_TIMER_ABSTIME was set in settime_flags or not. Is it OK?

Hi Vladimir! Well it_value returns remaining time so it's up to user to
adjust this value when restore with abs time. That said one can examinate
if abs flag was set and restore accordingly. If this is vague I'm open
to change it to more clear way. Ideas?

Re: [patch 1/3] timerfd: Implement show_fdinfo method

[Vladimir Davydov]

On 04/08/2014 10:42 AM, Cyrill Gorcunov wrote:
> On Tue, Apr 08, 2014 at 10:17:14AM +0400, Vladimir Davydov wrote:
> ...
>>> +static int timerfd_show(struct seq_file *m, struct file *file)
>>> +{
>>> +	struct timerfd_ctx *ctx = file->private_data;
>>> +	struct itimerspec t;
>>> +
>>> +	spin_lock_irq(&ctx->wqh.lock);
>>> +	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
>>> +	t.it_interval = ktime_to_timespec(ctx->tintv);
>>> +	spin_unlock_irq(&ctx->wqh.lock);
>>> +
>>> +	return seq_printf(m,
>>> +			  "clockid: %d\n"
>>> +			  "ticks: %llu\n"
>>> +			  "settime flags: 0%o\n"
>>> +			  "it_value: (%llu, %llu)\n"
>>> +			  "it_interval: (%llu, %llu)\n",
>> IMO, one would expect to setup the timer on restore by passing the
>> values of settime_flags, it_value, and it_interval obtained from the
>> fdinfo to sys_timerfd_settime, but this will be incorrect, because AFAIU
>> the it_value you report here is always relative to the current time, no
>> matter whether TFD_TIMER_ABSTIME was set in settime_flags or not. Is it OK?
> Hi Vladimir! Well it_value returns remaining time so it's up to user to
> adjust this value when restore with abs time. That said one can examinate
> if abs flag was set and restore accordingly. If this is vague I'm open
> to change it to more clear way. Ideas?

If it's intended, it should be documented explicitly I think. Currently
in the doc patch I see nothing about whether expiration time is absolute
or relative:

> 'it_value' and 'it_interval' are the expiration time and interval for the timer.

Thanks.

Re: [patch 1/3] timerfd: Implement show_fdinfo method

[Cyrill Gorcunov]

On Tue, Apr 08, 2014 at 10:54:45AM +0400, Vladimir Davydov wrote:
> > Hi Vladimir! Well it_value returns remaining time so it's up to user to
> > adjust this value when restore with abs time. That said one can examinate
> > if abs flag was set and restore accordingly. If this is vague I'm open
> > to change it to more clear way. Ideas?
> 
> If it's intended, it should be documented explicitly I think. Currently
> in the doc patch I see nothing about whether expiration time is absolute
> or relative:
> 
> > 'it_value' and 'it_interval' are the expiration time and interval for the timer.

I'll update, thanks!

[patch 2/3] docs: procfs -- Document timerfd output

[Cyrill Gorcunov]

[-- Attachment #1: timerfd-doc-fdinfo --]
[-- Type: text/plain, Size: 1437 bytes --]

CC: Shawn Landden <shawn@churchofgit.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <avagin@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 Documentation/filesystems/proc.txt |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

Index: linux-2.6.git/Documentation/filesystems/proc.txt
===================================================================
--- linux-2.6.git.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.git/Documentation/filesystems/proc.txt
@@ -1741,6 +1741,23 @@ pair provide additional information part
 	While the first three lines are mandatory and always printed, the rest is
 	optional and may be omitted if no marks created yet.
 
+	Timerfd files
+	~~~~~~~~~~~~~
+
+	pos:	0
+	flags:	02
+	mnt_id:	9
+	clockid: 0
+	ticks: 0
+	settime flags: 01
+	it_value: (0, 49406829)
+	it_interval: (1, 0)
+
+	where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
+	that have occurred [see timerfd_create(2) for details]. 'settime flags' are
+	flags in octal form used to setup the timer [see timerfd_settime(2) for
+	details]. 'it_value' and 'it_interval' are the expiration time and interval
+	for the timer.
 
 ------------------------------------------------------------------------------
 Configuring procfs

[patch 2/3] docs: procfs -- Document timerfd output, v2

[Cyrill Gorcunov]

CC: Shawn Landden <shawn@churchofgit.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <avagin@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---

Vladimir, would the below text be more clear?

 Documentation/filesystems/proc.txt |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

Index: linux-2.6.git/Documentation/filesystems/proc.txt
===================================================================
--- linux-2.6.git.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.git/Documentation/filesystems/proc.txt
@@ -1741,6 +1741,23 @@ pair provide additional information part
 	While the first three lines are mandatory and always printed, the rest is
 	optional and may be omitted if no marks created yet.
 
+	Timerfd files
+	~~~~~~~~~~~~~
+
+	pos:	0
+	flags:	02
+	mnt_id:	9
+	clockid: 0
+	ticks: 0
+	settime flags: 01
+	it_value: (0, 49406829)
+	it_interval: (1, 0)
+
+	where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
+	that have occurred [see timerfd_create(2) for details]. 'settime flags' are
+	flags in octal form used to setup the timer [see timerfd_settime(2) for
+	details]. 'it_value' is remaining time until the timer exiration.
+	'it_interval' is the interval for the timer.
 
 ------------------------------------------------------------------------------
 Configuring procfs

Re: [patch 2/3] docs: procfs -- Document timerfd output, v2

[Vladimir Davydov]

On 04/08/2014 11:43 AM, Cyrill Gorcunov wrote:
> CC: Shawn Landden <shawn@churchofgit.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Andrey Vagin <avagin@openvz.org>
> CC: Pavel Emelyanov <xemul@parallels.com>
> CC: Vladimir Davydov <vdavydov@parallels.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> ---
>
> Vladimir, would the below text be more clear?

It looks good to me.

Thanks.

>
>  Documentation/filesystems/proc.txt |   17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> Index: linux-2.6.git/Documentation/filesystems/proc.txt
> ===================================================================
> --- linux-2.6.git.orig/Documentation/filesystems/proc.txt
> +++ linux-2.6.git/Documentation/filesystems/proc.txt
> @@ -1741,6 +1741,23 @@ pair provide additional information part
>  	While the first three lines are mandatory and always printed, the rest is
>  	optional and may be omitted if no marks created yet.
>  
> +	Timerfd files
> +	~~~~~~~~~~~~~
> +
> +	pos:	0
> +	flags:	02
> +	mnt_id:	9
> +	clockid: 0
> +	ticks: 0
> +	settime flags: 01
> +	it_value: (0, 49406829)
> +	it_interval: (1, 0)
> +
> +	where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
> +	that have occurred [see timerfd_create(2) for details]. 'settime flags' are
> +	flags in octal form used to setup the timer [see timerfd_settime(2) for
> +	details]. 'it_value' is remaining time until the timer exiration.
> +	'it_interval' is the interval for the timer.
>  
>  ------------------------------------------------------------------------------
>  Configuring procfs

[patch 3/3] timerfd: Implement write method

[Cyrill Gorcunov]

[-- Attachment #1: timerfd-write-ticks --]
[-- Type: text/plain, Size: 1659 bytes --]

The read() of timerfd files allows to fetch the number of
timer ticks while there is no way to set it back from userspace.

To restore the timer state as it was at checkpoint moment we need
a way to setup ticks back. So as a counterpart of read() the write()
takes ticks number from the userspace and updates internal timer
ticks accordingly.

CC: Shawn Landden <shawn@churchofgit.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <avagin@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 fs/timerfd.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

Index: linux-2.6.git/fs/timerfd.c
===================================================================
--- linux-2.6.git.orig/fs/timerfd.c
+++ linux-2.6.git/fs/timerfd.c
@@ -311,10 +311,31 @@ static int timerfd_show(struct seq_file
 			  (unsigned long long)t.it_interval.tv_nsec);
 }
 
+
+static ssize_t timerfd_write(struct file *file, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	struct timerfd_ctx *ctx = file->private_data;
+	u64 ticks = 0;
+
+	if (count < sizeof(ticks))
+		return -EINVAL;
+
+	if (get_user(ticks, (u64 __user *) buf))
+		return -EFAULT;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	ctx->ticks = ticks;
+	spin_unlock_irq(&ctx->wqh.lock);
+
+	return sizeof(ticks);
+}
+
 static const struct file_operations timerfd_fops = {
 	.release	= timerfd_release,
 	.poll		= timerfd_poll,
 	.read		= timerfd_read,
+	.write		= timerfd_write,
 	.llseek		= noop_llseek,
 	.show_fdinfo	= timerfd_show,
 };

Re: [patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v2

[Cyrill Gorcunov]

On Mon, Apr 07, 2014 at 09:47:01PM +0400, Cyrill Gorcunov wrote:
> Hi, here is an updated series, changes mostly in show_fdinfo code which now
> produces a way more information (and documentation update). Please take a look
> once time permit. Thanks!

Hi, any new comments on this series?

Re: [patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v2

[Thomas Gleixner]

On Tue, 29 Apr 2014, Cyrill Gorcunov wrote:

> On Mon, Apr 07, 2014 at 09:47:01PM +0400, Cyrill Gorcunov wrote:
> > Hi, here is an updated series, changes mostly in show_fdinfo code which now
> > produces a way more information (and documentation update). Please take a look
> > once time permit. Thanks!
> 
> Hi, any new comments on this series?

Looks ok and I did not do anything about it, as I saw a "will update
in next version" from you in the discussion.

Thanks,

	tglx

Re: [patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v2

[Cyrill Gorcunov]

On Mon, Apr 28, 2014 at 10:59:34PM +0200, Thomas Gleixner wrote:
> On Tue, 29 Apr 2014, Cyrill Gorcunov wrote:
> 
> > On Mon, Apr 07, 2014 at 09:47:01PM +0400, Cyrill Gorcunov wrote:
> > > Hi, here is an updated series, changes mostly in show_fdinfo code which now
> > > produces a way more information (and documentation update). Please take a look
> > > once time permit. Thanks!
> > 
> > Hi, any new comments on this series?
> 
> Looks ok and I did not do anything about it, as I saw a "will update
> in next version" from you in the discussion.

Silly me :( I promised to update the series a bit, and forgot. Thanks, Thomas!

[patch 0/3] timerfd -- implement missing parts to checkpoint and restore timerfd state, v3

[Cyrill Gorcunov]

Hello! This is (I hope) the final version. Most changes from v2 are sitting in
documentation, where I tried to reflect that the time we're printing out is
remaining until the timer expiration. Please take a look.

[patch 2/3] docs: procfs -- Document timerfd output

[Cyrill Gorcunov]

[-- Attachment #1: timerfd-doc-fdinfo --]
[-- Type: text/plain, Size: 1617 bytes --]

CC: Shawn Landden <shawn@churchofgit.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <avagin@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 Documentation/filesystems/proc.txt |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

Index: linux-2.6.git/Documentation/filesystems/proc.txt
===================================================================
--- linux-2.6.git.orig/Documentation/filesystems/proc.txt
+++ linux-2.6.git/Documentation/filesystems/proc.txt
@@ -1741,6 +1741,25 @@ pair provide additional information part
 	While the first three lines are mandatory and always printed, the rest is
 	optional and may be omitted if no marks created yet.
 
+	Timerfd files
+	~~~~~~~~~~~~~
+
+	pos:	0
+	flags:	02
+	mnt_id:	9
+	clockid: 0
+	ticks: 0
+	settime flags: 01
+	it_value: (0, 49406829)
+	it_interval: (1, 0)
+
+	where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
+	that have occurred [see timerfd_create(2) for details]. 'settime flags' are
+	flags in octal form used to setup the timer [see timerfd_settime(2) for
+	details]. 'it_value' is remaining time until the timer exiration.
+	'it_interval' is the interval for the timer. Note the timer might be set
+	up with TFD_TIMER_ABSTIME option which will be shown in 'settime flags',
+	but 'it_value' still exhibit timer's remaining time.
 
 ------------------------------------------------------------------------------
 Configuring procfs