This is a note to let you know that I've just added the patch titled
iio: buffer: make sure O_NONBLOCK is respected
to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 3da1814184582ed0faf039275a3f02e6f69944ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nuno=20S=C3=A1?= <nuno.sa@xxxxxxxxxx>
Date: Thu, 16 Feb 2023 11:14:51 +0100
Subject: iio: buffer: make sure O_NONBLOCK is respected
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For output buffers, there's no guarantee that the buffer won't be full
in the first iteration of the loop in which case we would block
independently of userspace passing O_NONBLOCK or not. Fix it by always
checking the flag before going to sleep.
While at it (and as it's a bit related), refactored the loop so that the
stop condition is 'written != n', i.e, run the loop until all data has
been copied into the IIO buffers. This makes the code a bit simpler.
Fixes: 9eeee3b0bf190 ("iio: Add output buffer support")
Signed-off-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
Reviewed-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230216101452.591805-3-nuno.sa@xxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
drivers/iio/industrialio-buffer.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 6340d8e1430b..a7a080bed180 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -203,21 +203,24 @@ static ssize_t iio_buffer_write(struct file *filp, const char __user *buf,
break;
}
+ if (filp->f_flags & O_NONBLOCK) {
+ if (!written)
+ ret = -EAGAIN;
+ break;
+ }
+
wait_woken(&wait, TASK_INTERRUPTIBLE,
MAX_SCHEDULE_TIMEOUT);
continue;
}
ret = rb->access->write(rb, n - written, buf + written);
- if (ret == 0 && (filp->f_flags & O_NONBLOCK))
- ret = -EAGAIN;
+ if (ret < 0)
+ break;
- if (ret > 0) {
- written += ret;
- if (written != n && !(filp->f_flags & O_NONBLOCK))
- continue;
- }
- } while (ret == 0);
+ written += ret;
+
+ } while (written != n);
remove_wait_queue(&rb->pollq, &wait);
return ret < 0 ? ret : written;
--
2.40.0
