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Date: Wed, 5 Feb 2014 16:55:49 +0000
From: James Bottomley <jbottomley@...allels.com>
To: "eiichi.tsukata.xh@...achi.com" <eiichi.tsukata.xh@...achi.com>
CC: "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [REVIEW PATCH] scsi: Add 'retry_timeout' to avoid infinite
command retry
On Wed, 2014-02-05 at 14:47 +0900, Eiichi Tsukata wrote:
> Currently, scsi error handling in scsi_decide_disposition() tries to
> unconditionally requeue scsi command when device keeps some error state.
> This is because retryable errors are thought to be temporary and the scsi
> device will soon recover from those errors. Normally, such retry policy is
> appropriate because the device will soon recover from temporary error state.
This description isn't very descriptive. I presume you're talking about
the ADD_TO_MLQUEUE return from scsi_decide_disposition()?
> But there is no guarantee that device is able to recover from error state
> immediately. Some hardware error may prevent device from recovering.
> Therefore hardware error can results in infinite command retry loop.
If you're talking about ADD_TO_MLQUEUE, I don't believe this is correct:
there's a test in scsi_softirq_done() that makes sure the maximum
lifetime is retries*timeout and fails the command after that.
James
> This patchs adds 'retry_timeout' sysfs attribute which limits the retry time
> of each scsi command. Once scsi command retry time is longer than this timeout,
> the command is treated as failure. 'retry_timeout' is set to '0' by default
> which means no timeout set.
>
> Signed-off-by: Eiichi Tsukata <eiichi.tsukata.xh@...achi.com>
> Cc: "James E.J. Bottomley" <JBottomley@...allels.com>
> Cc: linux-scsi@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
> drivers/scsi/scsi_lib.c | 22 +++++++++++++++++++++-
> drivers/scsi/scsi_scan.c | 1 +
> drivers/scsi/scsi_sysfs.c | 32 ++++++++++++++++++++++++++++++++
> include/scsi/scsi.h | 1 +
> include/scsi/scsi_device.h | 1 +
> 5 files changed, 56 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 7bd7f0d..a9db69e 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1492,6 +1492,23 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
> blk_complete_request(req);
> }
>
> +/*
> + * Check if scsi command excessed retry timeout
> + */
> +static int scsi_retry_timed_out(struct scsi_cmnd *cmd)
> +{
> + unsigned int retry_timeout;
> +
> + retry_timeout = cmd->device->retry_timeout;
> + if (retry_timeout &&
> + time_before(cmd->jiffies_at_alloc + retry_timeout, jiffies)) {
> + scmd_printk(KERN_INFO, cmd, "retry timeout\n");
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> static void scsi_softirq_done(struct request *rq)
> {
> struct scsi_cmnd *cmd = rq->special;
> @@ -1512,7 +1529,10 @@ static void scsi_softirq_done(struct request *rq)
> wait_for/HZ);
> disposition = SUCCESS;
> }
> -
> +
> + if (scsi_retry_timed_out(cmd))
> + disposition = FAILED;
> +
> scsi_log_completion(cmd, disposition);
>
> switch (disposition) {
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 307a811..4ab044a 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -925,6 +925,7 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
> sdev->no_dif = 1;
>
> sdev->eh_timeout = SCSI_DEFAULT_EH_TIMEOUT;
> + sdev->retry_timeout = SCSI_DEFAULT_RETRY_TIMEOUT;
>
> if (*bflags & BLIST_SKIP_VPD_PAGES)
> sdev->skip_vpd_pages = 1;
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 8ff62c2..eaa2118 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -627,6 +627,37 @@ sdev_store_eh_timeout(struct device *dev, struct device_attribute *attr,
> static DEVICE_ATTR(eh_timeout, S_IRUGO | S_IWUSR, sdev_show_eh_timeout, sdev_store_eh_timeout);
>
> static ssize_t
> +sdev_show_retry_timeout(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct scsi_device *sdev;
> + sdev = to_scsi_device(dev);
> + return snprintf(buf, 20, "%u\n", sdev->retry_timeout / HZ);
> +}
> +
> +static ssize_t
> +sdev_store_retry_timeout(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct scsi_device *sdev;
> + unsigned int retry_timeout;
> + int err;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> + sdev = to_scsi_device(dev);
> + err = kstrtouint(buf, 10, &retry_timeout);
> + if (err)
> + return err;
> + sdev->retry_timeout = retry_timeout * HZ;
> +
> + return count;
> +}
> +static DEVICE_ATTR(retry_timeout, S_IRUGO | S_IWUSR,
> + sdev_show_retry_timeout, sdev_store_retry_timeout);
> +
> +static ssize_t
> store_rescan_field (struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> {
> @@ -797,6 +828,7 @@ static struct attribute *scsi_sdev_attrs[] = {
> &dev_attr_state.attr,
> &dev_attr_timeout.attr,
> &dev_attr_eh_timeout.attr,
> + &dev_attr_retry_timeout.attr,
> &dev_attr_iocounterbits.attr,
> &dev_attr_iorequest_cnt.attr,
> &dev_attr_iodone_cnt.attr,
> diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
> index 66d42ed..545408d 100644
> --- a/include/scsi/scsi.h
> +++ b/include/scsi/scsi.h
> @@ -16,6 +16,7 @@ struct scsi_cmnd;
>
> enum scsi_timeouts {
> SCSI_DEFAULT_EH_TIMEOUT = 10 * HZ,
> + SCSI_DEFAULT_RETRY_TIMEOUT = 0, /* disabled by default */
> };
>
> /*
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index d65fbec..04fc5ee 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -121,6 +121,7 @@ struct scsi_device {
> * pass settings from slave_alloc to scsi
> * core. */
> unsigned int eh_timeout; /* Error handling timeout */
> + unsigned int retry_timeout; /* Command retry timeout */
> unsigned writeable:1;
> unsigned removable:1;
> unsigned changed:1; /* Data invalid due to media change */
--
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