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|
Subject: AIO/POLL interaction
From: http://xenbits.xensource.com/xen-3.1-testing.hg (tip 15042)
Acked-by: jbeulich@novell.com
---
fs/aio.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++----
include/linux/aio.h | 5 ++
2 files changed, 116 insertions(+), 9 deletions(-)
--- a/fs/aio.c 2007-08-27 12:09:26.000000000 -0400
+++ b/fs/aio.c 2007-08-27 14:01:24.000000000 -0400
@@ -36,6 +36,11 @@
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
+#ifdef CONFIG_EPOLL
+#include <linux/poll.h>
+#include <linux/anon_inodes.h>
+#endif
+
#if DEBUG > 1
#define dprintk printk
#else
@@ -1009,6 +1014,11 @@ put_rq:
if (waitqueue_active(&ctx->wait))
wake_up(&ctx->wait);
+#ifdef CONFIG_EPOLL
+ if (ctx->file && waitqueue_active(&ctx->poll_wait))
+ wake_up(&ctx->poll_wait);
+#endif
+
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
return ret;
}
@@ -1016,6 +1026,8 @@ put_rq:
/* aio_read_evt
* Pull an event off of the ioctx's event ring. Returns the number of
* events fetched (0 or 1 ;-)
+ * If ent parameter is 0, just returns the number of events that would
+ * be fetched.
* FIXME: make this use cmpxchg.
* TODO: make the ringbuffer user mmap()able (requires FIXME).
*/
@@ -1038,13 +1050,18 @@ static int aio_read_evt(struct kioctx *i
head = ring->head % info->nr;
if (head != ring->tail) {
- struct io_event *evp = aio_ring_event(info, head, KM_USER1);
- *ent = *evp;
- head = (head + 1) % info->nr;
- smp_mb(); /* finish reading the event before updatng the head */
- ring->head = head;
- ret = 1;
- put_aio_ring_event(evp, KM_USER1);
+ if (ent) { /* event requested */
+ struct io_event *evp =
+ aio_ring_event(info, head, KM_USER1);
+ *ent = *evp;
+ head = (head + 1) % info->nr;
+ /* finish reading the event before updatng the head */
+ smp_mb();
+ ring->head = head;
+ ret = 1;
+ put_aio_ring_event(evp, KM_USER1);
+ } else /* only need to know availability */
+ ret = 1;
}
spin_unlock(&info->ring_lock);
@@ -1227,9 +1244,78 @@ static void io_destroy(struct kioctx *io
aio_cancel_all(ioctx);
wait_for_all_aios(ioctx);
+#ifdef CONFIG_EPOLL
+ /* forget the poll file, but it's up to the user to close it */
+ if (ioctx->file) {
+ ioctx->file->private_data = 0;
+ ioctx->file = 0;
+ }
+#endif
put_ioctx(ioctx); /* once for the lookup */
}
+#ifdef CONFIG_EPOLL
+
+static int aio_queue_fd_close(struct inode *inode, struct file *file)
+{
+ struct kioctx *ioctx = file->private_data;
+ if (ioctx) {
+ file->private_data = 0;
+ spin_lock_irq(&ioctx->ctx_lock);
+ ioctx->file = 0;
+ spin_unlock_irq(&ioctx->ctx_lock);
+ }
+ return 0;
+}
+
+static unsigned int aio_queue_fd_poll(struct file *file, poll_table *wait)
+{ unsigned int pollflags = 0;
+ struct kioctx *ioctx = file->private_data;
+
+ if (ioctx) {
+
+ spin_lock_irq(&ioctx->ctx_lock);
+ /* Insert inside our poll wait queue */
+ poll_wait(file, &ioctx->poll_wait, wait);
+
+ /* Check our condition */
+ if (aio_read_evt(ioctx, 0))
+ pollflags = POLLIN | POLLRDNORM;
+ spin_unlock_irq(&ioctx->ctx_lock);
+ }
+
+ return pollflags;
+}
+
+static const struct file_operations aioq_fops = {
+ .release = aio_queue_fd_close,
+ .poll = aio_queue_fd_poll
+};
+
+/* make_aio_fd:
+ * Create a file descriptor that can be used to poll the event queue.
+ * Based on the excellent epoll code.
+ */
+
+static int make_aio_fd(struct kioctx *ioctx)
+{
+ int error, fd;
+ struct inode *inode;
+ struct file *file;
+
+ error = anon_inode_getfd(&fd, &inode, &file, "[aioq]",
+ &aioq_fops, ioctx);
+ if (error)
+ return error;
+
+ /* associate the file with the IO context */
+ ioctx->file = file;
+ init_waitqueue_head(&ioctx->poll_wait);
+ return fd;
+}
+#endif
+
+
/* sys_io_setup:
* Create an aio_context capable of receiving at least nr_events.
* ctxp must not point to an aio_context that already exists, and
@@ -1242,18 +1328,30 @@ static void io_destroy(struct kioctx *io
* resources are available. May fail with -EFAULT if an invalid
* pointer is passed for ctxp. Will fail with -ENOSYS if not
* implemented.
+ *
+ * To request a selectable fd, the user context has to be initialized
+ * to 1, instead of 0, and the return value is the fd.
+ * This keeps the system call compatible, since a non-zero value
+ * was not allowed so far.
*/
asmlinkage long sys_io_setup(unsigned nr_events, aio_context_t __user *ctxp)
{
struct kioctx *ioctx = NULL;
unsigned long ctx;
long ret;
+ int make_fd = 0;
ret = get_user(ctx, ctxp);
if (unlikely(ret))
goto out;
ret = -EINVAL;
+#ifdef CONFIG_EPOLL
+ if (ctx == 1) {
+ make_fd = 1;
+ ctx = 0;
+ }
+#endif
if (unlikely(ctx || nr_events == 0)) {
pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
ctx, nr_events);
@@ -1264,8 +1362,12 @@ asmlinkage long sys_io_setup(unsigned nr
ret = PTR_ERR(ioctx);
if (!IS_ERR(ioctx)) {
ret = put_user(ioctx->user_id, ctxp);
- if (!ret)
- return 0;
+#ifdef CONFIG_EPOLL
+ if (make_fd && ret >= 0)
+ ret = make_aio_fd(ioctx);
+#endif
+ if (ret >= 0)
+ return ret;
get_ioctx(ioctx); /* io_destroy() expects us to hold a ref */
io_destroy(ioctx);
--- a/include/linux/aio.h 2007-08-27 12:09:26.000000000 -0400
+++ b/include/linux/aio.h 2007-08-27 14:01:24.000000000 -0400
@@ -201,6 +201,11 @@ struct kioctx {
struct aio_ring_info ring_info;
struct delayed_work wq;
+#ifdef CONFIG_EPOLL
+ // poll integration
+ wait_queue_head_t poll_wait;
+ struct file *file;
+#endif
};
/* prototypes */
|
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