[patch 1/4] timerfd: Implement show_fdinfo method

From: Cyrill Gorcunov
Date: Tue Jul 15 2014 - 17:59:09 EST

For checkpoint/restore of timerfd files we need to know how exactly
the timer were armed, to be able to recreate it on restore stage.
Thus implement show_fdinfo method which provides enough information
for that.

One of significant changes I think is the addition of @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 too.

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

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

v3 (by tglx@):
- don't forget to use CONFIG_PROC_FS

v4 (by akpm@):
-Use define timerfd_show NULL for non c/r config

CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Andrey Vagin <avagin@xxxxxxxxxx>
CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
CC: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
fs/timerfd.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 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 +287,40 @@ 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);
+#define timerfd_show NULL
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)

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