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>

diff --git a/fs/timerfd.c b/fs/timerfd.c
index 0013142c04759b527485f2abde83c084e17a7f8f..77183f047f65cb885153a15771b691ff0d25355f 100644 (file)
--- 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)