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Subject[PATCH] EPOLL_CTL_SET operatin for epoll_ctl when using EPOLLONESHOT
Date
Simplify userspace by eliminating the need to track whether a specific
filehandle was added to epoll already and only needs to be re-arm
after being internally disabled by EPOLLONESHOT.

EPOLL_CLT_SET can be used to add or modify a filehandle in epoll
using the kernel's internal tracking to apply the right equivalent
operation to EPOLL_CTL_ADD or EPOLL_CTL_MOD.

Signed-off-by: Carlo Marcelo Arenas Belon <carenas@sajinet.com.pe>
---
fs/eventpoll.c | 9 ++++++++-
include/linux/eventpoll.h | 1 +
2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 085c5c0..afa6972 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -799,7 +799,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
* If the event mask does not contain any poll(2) event, we consider the
* descriptor to be disabled. This condition is likely the effect of the
* EPOLLONESHOT bit that disables the descriptor when an event is received,
- * until the next EPOLL_CTL_MOD will be issued.
+ * until the next EPOLL_CTL_MOD or EPOLL_CTL_SET will be issued.
*/
if (!(epi->event.events & ~EP_PRIVATE_BITS))
goto out_unlock;
@@ -1302,6 +1302,13 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
} else
error = -ENOENT;
break;
+ case EPOLL_CTL_SET:
+ epds.events |= POLLERR | POLLHUP;
+ if (epi)
+ error = ep_modify(ep, epi, &epds);
+ else
+ error = ep_insert(ep, &epds, tfile, fd);
+ break;
}
mutex_unlock(&ep->mtx);

diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index f6856a5..59758c0 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -25,6 +25,7 @@
#define EPOLL_CTL_ADD 1
#define EPOLL_CTL_DEL 2
#define EPOLL_CTL_MOD 3
+#define EPOLL_CTL_SET 4

/* Set the One Shot behaviour for the target file descriptor */
#define EPOLLONESHOT (1 << 30)
--
1.6.3.3


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