@@ -5,6 +5,7 @@
* Implements an efficient asynchronous io interface.
*
* Copyright 2000, 2001, 2002 Red Hat, Inc. All Rights Reserved.
+ * Copyright 2018 Christoph Hellwig.
*
* See ../COPYING for licensing terms.
*/
@@ -165,10 +166,21 @@ struct fsync_iocb {
bool datasync;
};
+struct poll_iocb {
+ struct file *file;
+ struct wait_queue_head *head;
+ __poll_t events;
+ bool woken;
+ bool cancelled;
+ struct wait_queue_entry wait;
+ struct work_struct work;
+};
+
struct aio_kiocb {
union {
struct kiocb rw;
struct fsync_iocb fsync;
+ struct poll_iocb poll;
};
struct kioctx *ki_ctx;
@@ -1601,6 +1613,169 @@ static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool datasync)
return 0;
}
+static inline void aio_poll_complete(struct aio_kiocb *iocb, __poll_t mask)
+{
+ struct file *file = iocb->poll.file;
+
+ aio_complete(iocb, mangle_poll(mask), 0);
+ fput(file);
+}
+
+static void aio_poll_complete_work(struct work_struct *work)
+{
+ struct poll_iocb *req = container_of(work, struct poll_iocb, work);
+ struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
+ struct poll_table_struct pt = { ._key = req->events };
+ struct kioctx *ctx = iocb->ki_ctx;
+ __poll_t mask = 0;
+
+ if (!READ_ONCE(req->cancelled))
+ mask = vfs_poll(req->file, &pt) & req->events;
+
+ /*
+ * Note that ->ki_cancel callers also delete iocb from active_reqs after
+ * calling ->ki_cancel. We need the ctx_lock roundtrip here to
+ * synchronize with them. In the cancellation case the list_del_init
+ * itself is not actually needed, but harmless so we keep it in to
+ * avoid further branches in the fast path.
+ */
+ spin_lock_irq(&ctx->ctx_lock);
+ if (!mask && !READ_ONCE(req->cancelled)) {
+ add_wait_queue(req->head, &req->wait);
+ spin_unlock_irq(&ctx->ctx_lock);
+ return;
+ }
+ list_del_init(&iocb->ki_list);
+ spin_unlock_irq(&ctx->ctx_lock);
+
+ aio_poll_complete(iocb, mask);
+}
+
+/* assumes we are called with irqs disabled */
+static int aio_poll_cancel(struct kiocb *iocb)
+{
+ struct aio_kiocb *aiocb = container_of(iocb, struct aio_kiocb, rw);
+ struct poll_iocb *req = &aiocb->poll;
+
+ spin_lock(&req->head->lock);
+ WRITE_ONCE(req->cancelled, true);
+ if (!list_empty(&req->wait.entry)) {
+ list_del_init(&req->wait.entry);
+ schedule_work(&aiocb->poll.work);
+ }
+ spin_unlock(&req->head->lock);
+
+ return 0;
+}
+
+static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
+ void *key)
+{
+ struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
+ __poll_t mask = key_to_poll(key);
+
+ req->woken = true;
+
+ /* for instances that support it check for an event match first: */
+ if (mask && !(mask & req->events))
+ return 0;
+
+ list_del_init(&req->wait.entry);
+ schedule_work(&req->work);
+ return 1;
+}
+
+struct aio_poll_table {
+ struct poll_table_struct pt;
+ struct aio_kiocb *iocb;
+ int error;
+};
+
+static void
+aio_poll_queue_proc(struct file *file, struct wait_queue_head *head,
+ struct poll_table_struct *p)
+{
+ struct aio_poll_table *pt = container_of(p, struct aio_poll_table, pt);
+
+ /* multiple wait queues per file are not supported */
+ if (unlikely(pt->iocb->poll.head)) {
+ pt->error = -EINVAL;
+ return;
+ }
+
+ pt->error = 0;
+ pt->iocb->poll.head = head;
+ add_wait_queue(head, &pt->iocb->poll.wait);
+}
+
+static ssize_t aio_poll(struct aio_kiocb *aiocb, struct iocb *iocb)
+{
+ struct kioctx *ctx = aiocb->ki_ctx;
+ struct poll_iocb *req = &aiocb->poll;
+ struct aio_poll_table apt;
+ __poll_t mask;
+
+ /* reject any unknown events outside the normal event mask. */
+ if ((u16)iocb->aio_buf != iocb->aio_buf)
+ return -EINVAL;
+ /* reject fields that are not defined for poll */
+ if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags)
+ return -EINVAL;
+
+ INIT_WORK(&req->work, aio_poll_complete_work);
+ req->events = demangle_poll(iocb->aio_buf) | EPOLLERR | EPOLLHUP;
+ req->file = fget(iocb->aio_fildes);
+ if (unlikely(!req->file))
+ return -EBADF;
+
+ apt.pt._qproc = aio_poll_queue_proc;
+ apt.pt._key = req->events;
+ apt.iocb = aiocb;
+ apt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */
+
+ /* initialized the list so that we can do list_empty checks */
+ INIT_LIST_HEAD(&req->wait.entry);
+ init_waitqueue_func_entry(&req->wait, aio_poll_wake);
+
+ /* one for removal from waitqueue, one for this function */
+ refcount_set(&aiocb->ki_refcnt, 2);
+
+ mask = vfs_poll(req->file, &apt.pt) & req->events;
+ if (unlikely(!req->head)) {
+ /* we did not manage to set up a waitqueue, done */
+ goto out;
+ }
+
+ spin_lock_irq(&ctx->ctx_lock);
+ spin_lock(&req->head->lock);
+ if (req->woken) {
+ /* wake_up context handles the rest */
+ mask = 0;
+ apt.error = 0;
+ } else if (mask || apt.error) {
+ /* if we get an error or a mask we are done */
+ WARN_ON_ONCE(list_empty(&req->wait.entry));
+ list_del_init(&req->wait.entry);
+ } else {
+ /* actually waiting for an event */
+ list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
+ aiocb->ki_cancel = aio_poll_cancel;
+ }
+ spin_unlock(&req->head->lock);
+ spin_unlock_irq(&ctx->ctx_lock);
+
+out:
+ if (unlikely(apt.error)) {
+ fput(req->file);
+ return apt.error;
+ }
+
+ if (mask)
+ aio_poll_complete(aiocb, mask);
+ iocb_put(aiocb);
+ return 0;
+}
+
static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
bool compat)
{
@@ -1674,6 +1849,9 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
case IOCB_CMD_FDSYNC:
ret = aio_fsync(&req->fsync, &iocb, true);
break;
+ case IOCB_CMD_POLL:
+ ret = aio_poll(req, &iocb);
+ break;
default:
pr_debug("invalid aio operation %d\n", iocb.aio_lio_opcode);
ret = -EINVAL;
@@ -38,10 +38,8 @@ enum {
IOCB_CMD_PWRITE = 1,
IOCB_CMD_FSYNC = 2,
IOCB_CMD_FDSYNC = 3,
- /* These two are experimental.
- * IOCB_CMD_PREADX = 4,
- * IOCB_CMD_POLL = 5,
- */
+ /* 4 was the experimental IOCB_CMD_PREADX */
+ IOCB_CMD_POLL = 5,
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,