Commit 12aceb89 authored by Jens Axboe's avatar Jens Axboe Committed by Al Viro
Browse files

eventfd: convert to f_op->read_iter() 



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.

[missing include added]

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8f3d9f35

fs/eventfd.c

+38 −26
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/proc_fs.h>

#include <linux/seq_file.h>

#include <linux/idr.h>

#include <linux/uio.h>



DEFINE_PER_CPU(int, eventfd_wake_count);
@@ -216,32 +217,32 @@ 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 +251,14 @@ 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);

	}

	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 +327,7 @@ 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 +404,7 @@ 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 +424,24 @@ 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;

}

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