[PATCH] timerfd: show procfs fdinfo helper

[PATCH] timerfd: show procfs fdinfo helper

[Shawn Landden]

| pos:	0
| flags:	02004002
| clockid:	0

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Shawn Landden <shawn@churchofgit.com>
---
 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);
+
+	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

Re: [CRIU] [PATCH] timerfd: show procfs fdinfo helper

[Andrey Wagin]

2013/12/24 Shawn Landden <shawn@churchofgit.com>:
> | pos:  0
> | flags:        02004002
> | clockid:      0
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Shawn Landden <shawn@churchofgit.com>
> ---
>  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.

> +
> +       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
>
> _______________________________________________
> CRIU mailing list
> CRIU@openvz.org
> https://lists.openvz.org/mailman/listinfo/criu

Re: [CRIU] [PATCH] timerfd: show procfs fdinfo helper

[Andrew Vagin]

On Mon, Feb 03, 2014 at 01:24:41AM +0000, shawn@churchofgit.com wrote:
>     ---- Original Message ----
>     From: "Andrey Wagin" <avagin@gmail.com>
>     To: "Shawn Landden" <shawn@churchofgit.com>
>     CC: "LKML" <linux-kernel@vger.kernel.org>, "criu@openvz.org"
>     <criu@openvz.org>, "Alexander Viro" <viro@zeniv.linux.org.uk>,
>     linux-fsdevel@vger.kernel.org, "Thomas Gleixner" <tglx@linutronix.de>
>     Sent: Wed, Dec 25, 2013, 12:46 AM
>     Subject: Re: [CRIU] [PATCH] timerfd: show procfs fdinfo helper
> 
> 
>     2013/12/24 Shawn Landden <shawn@churchofgit.com>:
> 
>         | pos:  0
>         | flags:        02004002
>         | clockid:      0
> 
>         Cc: Thomas Gleixner <tglx@linutronix.de>
>         Cc: Alexander Viro <viro@zeniv.linux.org.uk>
>         Signed-off-by: Shawn Landden <shawn@churchofgit.com>
>         ---
>         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
> 
>         _______________________________________________
>         CRIU mailing list
>         CRIU@openvz.org
>         https://lists.openvz.org/mailman/listinfo/criu
> 

> _______________________________________________
> CRIU mailing list
> CRIU@openvz.org
> https://lists.openvz.org/mailman/listinfo/criu

[PATCH] timerfd: show procfs fdinfo helper, and now accepts write()

[Shawn Landden]

| pos:	0
| flags:	02004002
| clockid:	0
| ticks:        6

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Shawn Landden <shawn@churchofgit.com>
---
 fs/timerfd.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/fs/timerfd.c b/fs/timerfd.c
index 9293121..2e81bdb 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 {
@@ -284,10 +285,73 @@ 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;
+
+	seq_printf(m, "clockid:\t%d\n"
+		      "ticks:\t%llu\n", ctx->clockid, ctx->ticks);
+
+	return 0;
+}
+#endif
+
+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;
+	ssize_t res;
+	__u64 ucnt;
+	DECLARE_WAITQUEUE(wait, current);
+
+	if (count < sizeof(ucnt))
+		return -EINVAL;
+	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
+		return -EFAULT;
+	if (ucnt == ULLONG_MAX)
+		return -EINVAL;
+	spin_lock_irq(&ctx->wqh.lock);
+	res = -EAGAIN;
+	if (ULLONG_MAX - ctx->ticks > ucnt)
+		res = sizeof(ucnt);
+	else if (!(file->f_flags & O_NONBLOCK)) {
+		__add_wait_queue(&ctx->wqh, &wait);
+		for (res = 0;;) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			if (ULLONG_MAX - ctx->ticks > ucnt) {
+				res = sizeof(ucnt);
+				break;
+			}
+			if (signal_pending(current)) {
+				res = -ERESTARTSYS;
+				break;
+			}
+			spin_unlock_irq(&ctx->wqh.lock);
+			schedule();
+			spin_lock_irq(&ctx->wqh.lock);
+		}
+		__remove_wait_queue(&ctx->wqh, &wait);
+		__set_current_state(TASK_RUNNING);
+	}
+	if (likely(res > 0)) {
+		ctx->ticks += ucnt;
+		if (waitqueue_active(&ctx->wqh))
+			wake_up_locked_poll(&ctx->wqh, POLLIN);
+	}
+	spin_unlock_irq(&ctx->wqh.lock);
+
+	return res;
+}
+
 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,
+	.write		= timerfd_write,
 	.llseek		= noop_llseek,
 };
 
-- 
1.8.5.2.297.g3e57c29

Re: [PATCH] timerfd: show procfs fdinfo helper, and now accepts write()

[Thomas Gleixner]

On Mon, 3 Feb 2014, Shawn Landden wrote:

> | pos:	0
> | flags:	02004002
> | clockid:	0
> | ticks:        6

This changelog is completely useless. It neither explains WHY we need
to expose that fdinfo nor WHAT the write function is supposed to do.

Aside of that the code lacks any comment and there is no documentation
for the new user ABI.

> Signed-off-by: Shawn Landden <shawn@churchofgit.com>

I'm not going to find and read the bible of the churchofgit to figure
out what this is all about.

Thanks,

	tglx