epoll: convert internal api to timespec64

Patch series "add epoll_pwait2 syscall", v4.

Enable nanosecond timeouts for epoll.

Analogous to pselect and ppoll, introduce an epoll_wait syscall
variant that takes a struct timespec instead of int timeout.

This patch (of 4):

Make epoll more consistent with select/poll: pass along the timeout as
timespec64 pointer.

In anticipation of additional changes affecting all three polling
mechanisms:

- add epoll_pwait2 syscall with timespec semantics,
  and share poll_select_set_timeout implementation.
- compute slack before conversion to absolute time,
  to save one ktime_get_ts64 call.

Link: https://lkml.kernel.org/r/20201121144401.3727659-1-willemdebruijn.kernel@gmail.com
Link: https://lkml.kernel.org/r/20201121144401.3727659-2-willemdebruijn.kernel@gmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9efb553..1ba4066 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1712,15 +1712,25 @@ static int ep_send_events(struct eventpoll *ep,
        return res;
 }
 
-static inline struct timespec64 ep_set_mstimeout(long ms)
+static struct timespec64 *ep_timeout_to_timespec(struct timespec64 *to, long ms)
 {
-       struct timespec64 now, ts = {
-               .tv_sec = ms / MSEC_PER_SEC,
-               .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
-       };
+       struct timespec64 now;
+
+       if (ms < 0)
+               return NULL;
+
+       if (!ms) {
+               to->tv_sec = 0;
+               to->tv_nsec = 0;
+               return to;
+       }
+
+       to->tv_sec = ms / MSEC_PER_SEC;
+       to->tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC);
 
        ktime_get_ts64(&now);
-       return timespec64_add_safe(now, ts);
+       *to = timespec64_add_safe(now, *to);
+       return to;
 }
 
 /**
@@ -1732,8 +1742,8 @@ static inline struct timespec64 ep_set_mstimeout(long ms)
  *          stored.
  * @maxevents: Size (in terms of number of events) of the caller event buffer.
  * @timeout: Maximum timeout for the ready events fetch operation, in
- *           milliseconds. If the @timeout is zero, the function will not block,
- *           while if the @timeout is less than zero, the function will block
+ *           timespec. If the timeout is zero, the function will not block,
+ *           while if the @timeout ptr is NULL, the function will block
  *           until at least one event has been retrieved (or an error
  *           occurred).
  *
@@ -1741,7 +1751,7 @@ static inline struct timespec64 ep_set_mstimeout(long ms)
  *          error code, in case of error.
  */
 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
-                  int maxevents, long timeout)
+                  int maxevents, struct timespec64 *timeout)
 {
        int res, eavail, timed_out = 0;
        u64 slack = 0;
@@ -1750,13 +1760,11 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 
        lockdep_assert_irqs_enabled();
 
-       if (timeout > 0) {
-               struct timespec64 end_time = ep_set_mstimeout(timeout);
-
-               slack = select_estimate_accuracy(&end_time);
+       if (timeout && (timeout->tv_sec | timeout->tv_nsec)) {
+               slack = select_estimate_accuracy(timeout);
                to = &expires;
-               *to = timespec64_to_ktime(end_time);
-       } else if (timeout == 0) {
+               *to = timespec64_to_ktime(*timeout);
+       } else if (timeout) {
                /*
                 * Avoid the unnecessary trip to the wait queue loop, if the
                 * caller specified a non blocking operation.
@@ -2175,7 +2183,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
  * part of the user space epoll_wait(2).
  */
 static int do_epoll_wait(int epfd, struct epoll_event __user *events,
-                        int maxevents, int timeout)
+                        int maxevents, struct timespec64 *to)
 {
        int error;
        struct fd f;
@@ -2209,7 +2217,7 @@ static int do_epoll_wait(int epfd, struct epoll_event __user *events,
        ep = f.file->private_data;
 
        /* Time to fish for events ... */
-       error = ep_poll(ep, events, maxevents, timeout);
+       error = ep_poll(ep, events, maxevents, to);
 
 error_fput:
        fdput(f);
@@ -2219,7 +2227,10 @@ error_fput:
 SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
                int, maxevents, int, timeout)
 {
-       return do_epoll_wait(epfd, events, maxevents, timeout);
+       struct timespec64 to;
+
+       return do_epoll_wait(epfd, events, maxevents,
+                            ep_timeout_to_timespec(&to, timeout));
 }
 
 /*
@@ -2230,6 +2241,7 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
                int, maxevents, int, timeout, const sigset_t __user *, sigmask,
                size_t, sigsetsize)
 {
+       struct timespec64 to;
        int error;
 
        /*
@@ -2240,7 +2252,9 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
        if (error)
                return error;
 
-       error = do_epoll_wait(epfd, events, maxevents, timeout);
+       error = do_epoll_wait(epfd, events, maxevents,
+                             ep_timeout_to_timespec(&to, timeout));
+
        restore_saved_sigmask_unless(error == -EINTR);
 
        return error;
@@ -2253,6 +2267,7 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
                        const compat_sigset_t __user *, sigmask,
                        compat_size_t, sigsetsize)
 {
+       struct timespec64 to;
        long err;
 
        /*
@@ -2263,7 +2278,9 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
        if (err)
                return err;
 
-       err = do_epoll_wait(epfd, events, maxevents, timeout);
+       err = do_epoll_wait(epfd, events, maxevents,
+                           ep_timeout_to_timespec(&to, timeout));
+
        restore_saved_sigmask_unless(err == -EINTR);
 
        return err;