While eventfd ->read() callback was replaced by ->read_iter() recently,
it still provides ->write() for writes. Since commit 4d03e3cc5982 ("fs:
don't allow kernel reads and writes without iter ops"), this prevents
kernel_write() to be used for eventfd and with set_fs() removal,
->write() cannot be easily called directly with a kernel buffer.
According to eventfd(2), eventfd descriptors are supposed to be (also)
used by kernel to notify userspace applications of events which now
requires ->write_iter() op to be available (and ->write() not to be).
Therefore convert eventfd_write() to ->write_iter() semantics. This
patch also cleans up the code in a similar way as commit 12aceb89b0bc
("eventfd: convert to f_op->read_iter()") did in read_iter().
Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
fs/eventfd.c | 43 +++++++++++++++++++++----------------------
1 file changed, 21 insertions(+), 22 deletions(-)
diff --git a/fs/eventfd.c b/fs/eventfd.c
index df466ef81ddd..35973d216847 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -261,35 +261,36 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
return sizeof(ucnt);
}
-static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
- loff_t *ppos)
+static ssize_t eventfd_write(struct kiocb *iocb, struct iov_iter *from)
{
+ struct file *file = iocb->ki_filp;
struct eventfd_ctx *ctx = file->private_data;
- ssize_t res;
__u64 ucnt;
DECLARE_WAITQUEUE(wait, current);
- if (count < sizeof(ucnt))
+ if (iov_iter_count(from) < sizeof(ucnt))
return -EINVAL;
- if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
+ if (unlikely(!copy_from_iter_full(&ucnt, sizeof(ucnt), from)))
return -EFAULT;
if (ucnt == ULLONG_MAX)
return -EINVAL;
spin_lock_irq(&ctx->wqh.lock);
- res = -EAGAIN;
- if (ULLONG_MAX - ctx->count > ucnt)
- res = sizeof(ucnt);
- else if (!(file->f_flags & O_NONBLOCK)) {
+ if (ULLONG_MAX - ctx->count <= ucnt) {
+ 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 (res = 0;;) {
+ for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
- if (ULLONG_MAX - ctx->count > ucnt) {
- res = sizeof(ucnt);
+ if (ULLONG_MAX - ctx->count > ucnt)
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();
@@ -298,14 +299,12 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
}
- if (likely(res > 0)) {
- ctx->count += ucnt;
- if (waitqueue_active(&ctx->wqh))
- wake_up_locked_poll(&ctx->wqh, EPOLLIN);
- }
+ ctx->count += ucnt;
+ if (waitqueue_active(&ctx->wqh))
+ wake_up_locked_poll(&ctx->wqh, EPOLLIN);
spin_unlock_irq(&ctx->wqh.lock);
- return res;
+ return sizeof(ucnt);
}
#ifdef CONFIG_PROC_FS
@@ -328,7 +327,7 @@ static const struct file_operations eventfd_fops = {
.release = eventfd_release,
.poll = eventfd_poll,
.read_iter = eventfd_read,
- .write = eventfd_write,
+ .write_iter = eventfd_write,
.llseek = noop_llseek,
};
--
2.29.2
