timerfd: Implement show_fdinfo method

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

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Link: http://lkml.kernel.org/r/20140715215703.114365649@openvz.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 33 insertions, 1 deletions

diff --git a/fs/timerfd.c b/fs/timerfd.c
index 0013142c0475..77183f047f65 100644
--- a/fs/timerfd.c
+++ b/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_ctx *ctx, int flags,
                 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 *file, char __user *buf, size_t count,
         return res;
 }
 
+#ifdef CONFIG_PROC_FS
+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);
+}
+#else
+#define timerfd_show NULL
+#endif
+
 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)