linux-kernel - Re: [PATCH] nvme: Export fast_io_fail

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Date:   Wed, 31 Mar 2021 20:34:31 +0000
From:   Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
To:     Daniel Wagner <dwagner@...e.de>
CC:     "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Hannes Reinecke <hare@...e.de>,
        Chao Leng <lengchao@...wei.com>,
        Victor Gladkov <Victor.Gladkov@...xia.com>
Subject: Re: [PATCH] nvme: Export fast_io_fail_tmo to sysfs

Daniel,

On 3/31/21 06:12, Daniel Wagner wrote:
> Commit 8c4dfea97f15 ("nvme-fabrics: reject I/O to offline device")
> introduced fast_io_fail_tmo but didn't export the value to sysfs. That
> means the value is hard coded during compile time. Export the timeout
> value to user space via sysfs to allow runtime configuration.
>
> Cc: Victor Gladkov <Victor.Gladkov@...xia.com>
> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>
> This patch is against nvme-5.13
>
> BTW, checkpatch complains with
>
>   WARNING: Symbolic permissions 'S_IRUGO | S_IWUSR' are not preferred. Consider using octal permissions '0644'.

For now keep the current style.

>
> Is this something we want to adapt to?
>
>  drivers/nvme/host/core.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 40215a0246e4..c8de0e37c7d9 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3696,6 +3696,36 @@ static ssize_t nvme_ctrl_reconnect_delay_store(struct device *dev,
>  static DEVICE_ATTR(reconnect_delay, S_IRUGO | S_IWUSR,
>  	nvme_ctrl_reconnect_delay_show, nvme_ctrl_reconnect_delay_store);
>  
> +static ssize_t nvme_ctrl_fast_io_fail_tmo_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
> +
> +	if (ctrl->opts->fast_io_fail_tmo == -1)
> +		return sprintf(buf, "off\n");
> +	return sprintf(buf, "%d\n", ctrl->opts->fast_io_fail_tmo);

do we need snprintf() for 2nd ?

> +}
> +
> +static ssize_t nvme_ctrl_fast_io_fail_tmo_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t count)
> +{
> +	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
> +	struct nvmf_ctrl_options *opts = ctrl->opts;
> +	int fast_io_fail_tmo, err;
> +
> +	err = kstrtoint(buf, 10, &fast_io_fail_tmo);
> +	if (err)
> +		return -EINVAL;
> +

since you are returning an error, you can remove next else if, this also
removes the extra line after above return. Something like this on the top
of yours totally untested :-

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c8de0e37c7d9..afa0a6790b52 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3717,7 +3717,7 @@ static ssize_t
nvme_ctrl_fast_io_fail_tmo_store(struct device *dev,
        if (err)
                return -EINVAL;
 
-       else if (fast_io_fail_tmo < 0)
+       if (fast_io_fail_tmo < 0)
                opts->fast_io_fail_tmo = -1;
        else
                opts->fast_io_fail_tmo = fast_io_fail_tmo;

> +	else if (fast_io_fail_tmo < 0)
> +		opts->fast_io_fail_tmo = -1;
> +	else
> +		opts->fast_io_fail_tmo = fast_io_fail_tmo;
> +	return count;
> +}
> +static DEVICE_ATTR(fast_io_fail_tmo, S_IRUGO | S_IWUSR,
> +	nvme_ctrl_fast_io_fail_tmo_show, nvme_ctrl_fast_io_fail_tmo_store);
> +
>  static struct attribute *nvme_dev_attrs[] = {
>  	&dev_attr_reset_controller.attr,
>  	&dev_attr_rescan_controller.attr,
> @@ -3715,6 +3745,7 @@ static struct attribute *nvme_dev_attrs[] = {
>  	&dev_attr_hostid.attr,
>  	&dev_attr_ctrl_loss_tmo.attr,
>  	&dev_attr_reconnect_delay.attr,
> +	&dev_attr_fast_io_fail_tmo.attr,
>  	NULL
>  };
>  
> -- 2.29.2