The patch titled
signal/timer/event: KAIO eventfd support example
has been removed from the -mm tree. Its filename was
signal-timer-event-fds-v9-kaio-eventfd-support-example.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: signal/timer/event: KAIO eventfd support example
From: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
This is an example about how to add eventfd support to the current KAIO code,
in order to enable KAIO to post readiness events to a pollable fd (hence
compatible with POSIX select/poll). The KAIO code simply signals the eventfd
fd when events are ready, and this triggers a POLLIN in the fd. This patch
uses a reserved for future use member of the struct iocb to pass an eventfd
file descriptor, that KAIO will use to post events every time a request
completes. At that point, an aio_getevents() will return the completed result
to a struct io_event. I made a quick test program to verify the patch, and it
runs fine here:
http://www.xmailserver.org/eventfd-aio-test.c
The test program uses poll(2), but it'd, of course, work with select and epoll
too.
This can allow to schedule both block I/O and other poll-able devices
requests, and wait for results using select/poll/epoll. In a typical
scenario, an application would submit KAIO request using aio_submit(), and
will also use epoll_ctl() on the whole other class of devices (that with the
addition of signals, timers and user events, now it's pretty much complete),
and then would:
epoll_wait(...);
for_each_event {
if (curr_event_is_kaiofd) {
aio_getevents();
dispatch_aio_events();
} else {
dispatch_epoll_event();
}
}
Signed-off-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/aio.c | 28 ++++++++++++++++++++++++++--
include/linux/aio.h | 6 ++++++
include/linux/aio_abi.h | 18 +++++++++++++++++-
3 files changed, 49 insertions(+), 3 deletions(-)
diff -puN fs/aio.c~signal-timer-event-fds-v9-kaio-eventfd-support-example fs/aio.c
--- a/fs/aio.c~signal-timer-event-fds-v9-kaio-eventfd-support-example
+++ a/fs/aio.c
@@ -30,6 +30,7 @@
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>
+#include <linux/eventfd.h>
#include <asm/kmap_types.h>
#include <asm/uaccess.h>
@@ -417,6 +418,7 @@ static struct kiocb fastcall *__aio_get_
req->private = NULL;
req->ki_iovec = NULL;
INIT_LIST_HEAD(&req->ki_run_list);
+ req->ki_eventfd = ERR_PTR(-EINVAL);
/* Check if the completion queue has enough free space to
* accept an event from this io.
@@ -458,6 +460,8 @@ static inline void really_put_req(struct
{
assert_spin_locked(&ctx->ctx_lock);
+ if (!IS_ERR(req->ki_eventfd))
+ fput(req->ki_eventfd);
if (req->ki_dtor)
req->ki_dtor(req);
if (req->ki_iovec != &req->ki_inline_vec)
@@ -942,6 +946,14 @@ int fastcall aio_complete(struct kiocb *
return 1;
}
+ /*
+ * Check if the user asked us to deliver the result through an
+ * eventfd. The eventfd_signal() function is safe to be called
+ * from IRQ context.
+ */
+ if (!IS_ERR(iocb->ki_eventfd))
+ eventfd_signal(iocb->ki_eventfd, 1);
+
info = &ctx->ring_info;
/* add a completion event to the ring buffer.
@@ -1526,8 +1538,7 @@ int fastcall io_submit_one(struct kioctx
ssize_t ret;
/* enforce forwards compatibility on users */
- if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2 ||
- iocb->aio_reserved3)) {
+ if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
pr_debug("EINVAL: io_submit: reserve field set\n");
return -EINVAL;
}
@@ -1551,6 +1562,19 @@ int fastcall io_submit_one(struct kioctx
fput(file);
return -EAGAIN;
}
+ if (iocb->aio_flags & IOCB_FLAG_RESFD) {
+ /*
+ * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
+ * instance of the file* now. The file descriptor must be
+ * an eventfd() fd, and will be signaled for each completed
+ * event using the eventfd_signal() function.
+ */
+ req->ki_eventfd = eventfd_fget((int) iocb->aio_resfd);
+ if (unlikely(IS_ERR(req->ki_eventfd))) {
+ ret = PTR_ERR(req->ki_eventfd);
+ goto out_put_req;
+ }
+ }
req->ki_filp = file;
ret = put_user(req->ki_key, &user_iocb->aio_key);
diff -puN include/linux/aio.h~signal-timer-event-fds-v9-kaio-eventfd-support-example include/linux/aio.h
--- a/include/linux/aio.h~signal-timer-event-fds-v9-kaio-eventfd-support-example
+++ a/include/linux/aio.h
@@ -119,6 +119,12 @@ struct kiocb {
struct list_head ki_list; /* the aio core uses this
* for cancellation */
+
+ /*
+ * If the aio_resfd field of the userspace iocb is not zero,
+ * this is the underlying file* to deliver event to.
+ */
+ struct file *ki_eventfd;
};
#define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY)
diff -puN include/linux/aio_abi.h~signal-timer-event-fds-v9-kaio-eventfd-support-example include/linux/aio_abi.h
--- a/include/linux/aio_abi.h~signal-timer-event-fds-v9-kaio-eventfd-support-example
+++ a/include/linux/aio_abi.h
@@ -45,6 +45,14 @@ enum {
IOCB_CMD_PWRITEV = 8,
};
+/*
+ * Valid flags for the "aio_flags" member of the "struct iocb".
+ *
+ * IOCB_FLAG_RESFD - Set if the "aio_resfd" member of the "struct iocb"
+ * is valid.
+ */
+#define IOCB_FLAG_RESFD (1 << 0)
+
/* read() from /dev/aio returns these structures. */
struct io_event {
__u64 data; /* the data field from the iocb */
@@ -84,7 +92,15 @@ struct iocb {
/* extra parameters */
__u64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */
- __u64 aio_reserved3;
+
+ /* flags for the "struct iocb" */
+ __u32 aio_flags;
+
+ /*
+ * if the IOCB_FLAG_RESFD flag of "aio_flags" is set, this is an
+ * eventfd to signal AIO readiness to
+ */
+ __u32 aio_resfd;
}; /* 64 bytes */
#undef IFBIG
_
Patches currently in -mm which might be from davidel@xxxxxxxxxxxxxxx are
origin.patch
compat-signalfd-and-timerfd-are-cond-syscalls.patch
x86_64-use-signalfd-and-timerfd-compat-syscalls.patch
-
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