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authorDavide Libenzi <davidel@xmailserver.org>2007-05-11 09:23:21 +0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-11 19:29:37 +0400
commit9c3060bedd84144653a2ad7bea32389f65598d40 (patch)
tree80336eb24be8458cda1f35ee752f05bc7c329fbb /fs/aio.c
parentfdb902b1225e1668315f38e96d2f439452c03a15 (diff)
downloadlinux-9c3060bedd84144653a2ad7bea32389f65598d40.tar.xz
signal/timer/event: KAIO eventfd support example
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@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c28
1 files changed, 26 insertions, 2 deletions
diff --git a/fs/aio.c b/fs/aio.c
index ac1c1587aa02..dbe699e9828c 100644
--- a/fs/aio.c
+++ b/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(struct kioctx *ctx)
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 kioctx *ctx, struct kiocb *req)
{
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 *iocb, long res, long res2)
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 *ctx, struct iocb __user *user_iocb,
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 *ctx, struct iocb __user *user_iocb,
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);