eventfd is using ->read() as it's file_operations read handler, but
this prevents passing in information about whether a given IO operation
is blocking or not. We can only use the file flags for that. To support
async (-EAGAIN/poll based) retries for io_uring, we need ->read_iter()
support. Convert eventfd to using ->read_iter().
With ->read_iter(), we can support IOCB_NOWAIT. Ensure the fd setup
is done such that we set file->f_mode with FMODE_NOWAIT.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
Since v3:
- Ensure we fiddle ->f_mode before doing fd_install() on the fd
Since v2:
- Cleanup eventfd_read() as per Al's suggestions
Since v1:
- Add FMODE_NOWAIT to the eventfd file
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 78e41c7c3d05..20f0fd4d56e1 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -216,32 +216,32 @@ int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *w
}
EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
-static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
- loff_t *ppos)
+static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
{
+ struct file *file = iocb->ki_filp;
struct eventfd_ctx *ctx = file->private_data;
- ssize_t res;
__u64 ucnt = 0;
DECLARE_WAITQUEUE(wait, current);
- if (count < sizeof(ucnt))
+ if (iov_iter_count(to) < sizeof(ucnt))
return -EINVAL;
-
spin_lock_irq(&ctx->wqh.lock);
- res = -EAGAIN;
- if (ctx->count > 0)
- res = sizeof(ucnt);
- else if (!(file->f_flags & O_NONBLOCK)) {
+ if (!ctx->count) {
+ if ((file->f_flags & O_NONBLOCK) ||
+ (iocb->ki_flags & IOCB_NOWAIT)) {
+ spin_unlock_irq(&ctx->wqh.lock);
+ return -EAGAIN;
+ }
__add_wait_queue(&ctx->wqh, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
- if (ctx->count > 0) {
- res = sizeof(ucnt);
+ if (ctx->count)
break;
- }
if (signal_pending(current)) {
- res = -ERESTARTSYS;
- break;
+ __remove_wait_queue(&ctx->wqh, &wait);
+ __set_current_state(TASK_RUNNING);
+ spin_unlock_irq(&ctx->wqh.lock);
+ return -ERESTARTSYS;
}
spin_unlock_irq(&ctx->wqh.lock);
schedule();
@@ -250,17 +250,14 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
}
- if (likely(res > 0)) {
- eventfd_ctx_do_read(ctx, &ucnt);
- if (waitqueue_active(&ctx->wqh))
- wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
- }
+ eventfd_ctx_do_read(ctx, &ucnt);
+ if (waitqueue_active(&ctx->wqh))
+ wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
spin_unlock_irq(&ctx->wqh.lock);
-
- if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
+ if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt)))
return -EFAULT;
- return res;
+ return sizeof(ucnt);
}
static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
@@ -329,7 +326,7 @@ static const struct file_operations eventfd_fops = {
#endif
.release = eventfd_release,
.poll = eventfd_poll,
- .read = eventfd_read,
+ .read_iter = eventfd_read,
.write = eventfd_write,
.llseek = noop_llseek,
};
@@ -406,6 +403,7 @@ EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
static int do_eventfd(unsigned int count, int flags)
{
struct eventfd_ctx *ctx;
+ struct file *file;
int fd;
/* Check the EFD_* constants for consistency. */
@@ -425,11 +423,24 @@ static int do_eventfd(unsigned int count, int flags)
ctx->flags = flags;
ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
- fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
- O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
+ flags &= EFD_SHARED_FCNTL_FLAGS;
+ flags |= O_RDWR;
+ fd = get_unused_fd_flags(flags);
if (fd < 0)
- eventfd_free_ctx(ctx);
+ goto err;
+
+ file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
+ if (IS_ERR(file)) {
+ put_unused_fd(fd);
+ fd = PTR_ERR(file);
+ goto err;
+ }
+ file->f_mode |= FMODE_NOWAIT;
+ fd_install(fd, file);
+ return fd;
+err:
+ eventfd_free_ctx(ctx);
return fd;
}
--
Jens Axboe
