eventfd: change int to __u64 in eventfd_signal()

eventfd_ctx->count is an __u64 counter which is allowed to reach
ULLONG_MAX.  eventfd_write() adds a __u64 value to "count", but the kernel
side eventfd_signal() only adds an int value to it.  Make them consistent.

[akpm@linux-foundation.org: update interface documentation]
Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 8 deletions

diff --git a/fs/eventfd.c b/fs/eventfd.c
index dba15fecf23e..d81b9f654086 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -46,20 +46,16 @@ struct eventfd_ctx {
  * value, and we signal this as overflow condition by returining a POLLERR
  * to poll(2).
  *
- * Returns @n in case of success, a non-negative number lower than @n in case
- * of overflow, or the following error codes:
- *
- * -EINVAL    : The value of @n is negative.
+ * Returns the amount by which the counter was incrememnted.  This will be less
+ * than @n if the counter has overflowed.
  */
-int eventfd_signal(struct eventfd_ctx *ctx, int n)
+__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
 {
         unsigned long flags;
 
-        if (n < 0)
-                return -EINVAL;
         spin_lock_irqsave(&ctx->wqh.lock, flags);
         if (ULLONG_MAX - ctx->count < n)
-                n = (int) (ULLONG_MAX - ctx->count);
+                n = ULLONG_MAX - ctx->count;
         ctx->count += n;
         if (waitqueue_active(&ctx->wqh))
                 wake_up_locked_poll(&ctx->wqh, POLLIN);