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authorDavide Libenzi <davidel@xmailserver.org>2007-05-11 01:23:21 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-11 11:29:37 -0400
commit9c3060bedd84144653a2ad7bea32389f65598d40 (patch)
tree80336eb24be8458cda1f35ee752f05bc7c329fbb /fs
parentfdb902b1225e1668315f38e96d2f439452c03a15 (diff)
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')
-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 @@
30#include <linux/highmem.h> 30#include <linux/highmem.h>
31#include <linux/workqueue.h> 31#include <linux/workqueue.h>
32#include <linux/security.h> 32#include <linux/security.h>
33#include <linux/eventfd.h>
33 34
34#include <asm/kmap_types.h> 35#include <asm/kmap_types.h>
35#include <asm/uaccess.h> 36#include <asm/uaccess.h>
@@ -417,6 +418,7 @@ static struct kiocb fastcall *__aio_get_req(struct kioctx *ctx)
417 req->private = NULL; 418 req->private = NULL;
418 req->ki_iovec = NULL; 419 req->ki_iovec = NULL;
419 INIT_LIST_HEAD(&req->ki_run_list); 420 INIT_LIST_HEAD(&req->ki_run_list);
421 req->ki_eventfd = ERR_PTR(-EINVAL);
420 422
421 /* Check if the completion queue has enough free space to 423 /* Check if the completion queue has enough free space to
422 * accept an event from this io. 424 * accept an event from this io.
@@ -458,6 +460,8 @@ static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
458{ 460{
459 assert_spin_locked(&ctx->ctx_lock); 461 assert_spin_locked(&ctx->ctx_lock);
460 462
463 if (!IS_ERR(req->ki_eventfd))
464 fput(req->ki_eventfd);
461 if (req->ki_dtor) 465 if (req->ki_dtor)
462 req->ki_dtor(req); 466 req->ki_dtor(req);
463 if (req->ki_iovec != &req->ki_inline_vec) 467 if (req->ki_iovec != &req->ki_inline_vec)
@@ -942,6 +946,14 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
942 return 1; 946 return 1;
943 } 947 }
944 948
949 /*
950 * Check if the user asked us to deliver the result through an
951 * eventfd. The eventfd_signal() function is safe to be called
952 * from IRQ context.
953 */
954 if (!IS_ERR(iocb->ki_eventfd))
955 eventfd_signal(iocb->ki_eventfd, 1);
956
945 info = &ctx->ring_info; 957 info = &ctx->ring_info;
946 958
947 /* add a completion event to the ring buffer. 959 /* 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,
1526 ssize_t ret; 1538 ssize_t ret;
1527 1539
1528 /* enforce forwards compatibility on users */ 1540 /* enforce forwards compatibility on users */
1529 if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2 || 1541 if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1530 iocb->aio_reserved3)) {
1531 pr_debug("EINVAL: io_submit: reserve field set\n"); 1542 pr_debug("EINVAL: io_submit: reserve field set\n");
1532 return -EINVAL; 1543 return -EINVAL;
1533 } 1544 }
@@ -1551,6 +1562,19 @@ int fastcall io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1551 fput(file); 1562 fput(file);
1552 return -EAGAIN; 1563 return -EAGAIN;
1553 } 1564 }
1565 if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1566 /*
1567 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1568 * instance of the file* now. The file descriptor must be
1569 * an eventfd() fd, and will be signaled for each completed
1570 * event using the eventfd_signal() function.
1571 */
1572 req->ki_eventfd = eventfd_fget((int) iocb->aio_resfd);
1573 if (unlikely(IS_ERR(req->ki_eventfd))) {
1574 ret = PTR_ERR(req->ki_eventfd);
1575 goto out_put_req;
1576 }
1577 }
1554 1578
1555 req->ki_filp = file; 1579 req->ki_filp = file;
1556 ret = put_user(req->ki_key, &user_iocb->aio_key); 1580 ret = put_user(req->ki_key, &user_iocb->aio_key);