2023-02-16 13:19:21

by Wen Yang

Subject: [PATCH] eventfd: use wait_event_interruptible_locked_irq() helper

From: Wen Yang <[email protected]>

wait_event_interruptible_locked_irq was introduced by commit 22c43c81a51e
("wait_event_interruptible_locked() interface"), but older code such as
eventfd_{write,read} still uses the open code implementation.
Inspired by commit 8120a8aadb20
("fs/timerfd.c: make use of wait_event_interruptible_locked_irq()"), this
patch replaces the open code implementation with a single macro call.

No functional change intended.

Signed-off-by: Wen Yang <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dylan Yudaken <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Fu Wei <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Michal Nazarewicz <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
fs/eventfd.c | 40 ++++++----------------------------------
1 file changed, 6 insertions(+), 34 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index 249ca6c0b784..2b6a8a4d80a1 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -228,7 +228,6 @@ 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;
__u64 ucnt = 0;
- DECLARE_WAITQUEUE(wait, current);

if (iov_iter_count(to) < sizeof(ucnt))
return -EINVAL;
@@ -239,23 +238,11 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
spin_unlock_irq(&ctx->wqh.lock);
return -EAGAIN;
}
- __add_wait_queue(&ctx->wqh, &wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
- if (ctx->count)
- break;
- if (signal_pending(current)) {
- __remove_wait_queue(&ctx->wqh, &wait);
- __set_current_state(TASK_RUNNING);
- spin_unlock_irq(&ctx->wqh.lock);
- return -ERESTARTSYS;
- }
+
+ if (wait_event_interruptible_locked_irq(ctx->wqh, ctx->count)) {
spin_unlock_irq(&ctx->wqh.lock);
- schedule();
- spin_lock_irq(&ctx->wqh.lock);
+ return -ERESTARTSYS;
}
- __remove_wait_queue(&ctx->wqh, &wait);
- __set_current_state(TASK_RUNNING);
}
eventfd_ctx_do_read(ctx, &ucnt);
current->in_eventfd = 1;
@@ -275,7 +262,6 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
struct eventfd_ctx *ctx = file->private_data;
ssize_t res;
__u64 ucnt;
- DECLARE_WAITQUEUE(wait, current);

if (count < sizeof(ucnt))
return -EINVAL;
@@ -288,23 +274,9 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
if (ULLONG_MAX - ctx->count > ucnt)
res = sizeof(ucnt);
else if (!(file->f_flags & O_NONBLOCK)) {
- __add_wait_queue(&ctx->wqh, &wait);
- for (res = 0;;) {
- set_current_state(TASK_INTERRUPTIBLE);
- if (ULLONG_MAX - ctx->count > ucnt) {
- res = sizeof(ucnt);
- break;
- }
- if (signal_pending(current)) {
- res = -ERESTARTSYS;
- break;
- }
- spin_unlock_irq(&ctx->wqh.lock);
- schedule();
- spin_lock_irq(&ctx->wqh.lock);
- }
- __remove_wait_queue(&ctx->wqh, &wait);
- __set_current_state(TASK_RUNNING);
+ res = wait_event_interruptible_locked_irq(
+ ctx->wqh, ULLONG_MAX - ctx->count > ucnt) ?
+ -ERESTARTSYS : sizeof(ucnt);
}
if (likely(res > 0)) {
ctx->count += ucnt;
--
2.37.2

2023-02-16 13:29:33

by Matthew Wilcox

Subject: Re: [PATCH] eventfd: use wait_event_interruptible_locked_irq() helper

On Thu, Feb 16, 2023 at 09:17:39PM +0800, [email protected] wrote:
> + res = wait_event_interruptible_locked_irq(
> + ctx->wqh, ULLONG_MAX - ctx->count > ucnt) ?
> + -ERESTARTSYS : sizeof(ucnt);

You've broken the line here in a weird way. I'd've done it as:

res = wait_event_interruptible_locked_irq(ctx->wqh,
ULLONG_MAX - ctx->count > ucnt) ?
-ERESTARTSYS : sizeof(ucnt));

... also the patch you've sent here doesn't even compile. Have you
tested it?

2023-02-16 13:33:23

by Matthew Wilcox

Subject: Re: [PATCH] eventfd: use wait_event_interruptible_locked_irq() helper

On Thu, Feb 16, 2023 at 01:29:00PM +0000, Matthew Wilcox wrote:
> On Thu, Feb 16, 2023 at 09:17:39PM +0800, [email protected] wrote:
> > + res = wait_event_interruptible_locked_irq(
> > + ctx->wqh, ULLONG_MAX - ctx->count > ucnt) ?
> > + -ERESTARTSYS : sizeof(ucnt);
>
> You've broken the line here in a weird way. I'd've done it as:
>
> res = wait_event_interruptible_locked_irq(ctx->wqh,
> ULLONG_MAX - ctx->count > ucnt) ?
> -ERESTARTSYS : sizeof(ucnt));
>
> ... also the patch you've sent here doesn't even compile. Have you
> tested it?

Sorry, I misread it. But I would have avoided use of the ?: operator
here ...

res = wait_event_interruptible_locked_irq(ctx->wqh,
ULLONG_MAX - ctx->count > ucnt);
if (res == 0)
res = sizeof(ucnt);