On 2/22/21 11:15 AM, Minwoo Im wrote:

On 21-02-22 07:41:55, Hannes Reinecke wrote:

quoted

In some setups like RAID we need to return an I/O error
once all paths are unavailable to allow the upper layers
to start their own error recovery (like redirecting I/O
to other mirrors).
This patch adds a sysfs attribute 'fail_if_no_path' to
allow the admin to enable that behaviour instead of the
current 'queue until a path becomes available' policy.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
  drivers/nvme/host/core.c      |  5 +++++
  drivers/nvme/host/multipath.c | 38 +++++++++++++++++++++++++++++++++--
  drivers/nvme/host/nvme.h      |  2 ++
  3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 5c1ec3bfb9d3..ef20029a46b2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c

@@ -3466,6 +3466,7 @@ static struct attribute *nvme_ns_id_attrs[] = {
  #ifdef CONFIG_NVME_MULTIPATH
  	&dev_attr_ana_grpid.attr,
  	&dev_attr_ana_state.attr,
+	&dev_attr_fail_if_no_path.attr,
  #endif
  	NULL,
  };

@@ -3496,6 +3497,10 @@ static umode_t nvme_ns_id_attrs_are_visible(struct kobject *kobj,
  		if (!nvme_ctrl_use_ana(nvme_get_ns_from_dev(dev)->ctrl))
  			return 0;
  	}
+	if (a == &dev_attr_fail_if_no_path.attr) {
+		if (dev_to_disk(dev)->fops == &nvme_bdev_ops)
+			return 0;
+	}
  #endif
  	return a->mode;
  }

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 0696319adaf6..35ed2f6d431b 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c

@@ -283,10 +283,13 @@ static bool nvme_available_path(struct nvme_ns_head *head)
  			continue;
  		switch (ns->ctrl->state) {
  		case NVME_CTRL_LIVE:
+			return true;

Hello Hannes,

May I ask there's any reason why LIVE state is not covered by the sysfs
attribute that this patch introduced ?  Wouldn't it be possible to have
no available paths (inaccessible) in LIVE state ?

Thanks! :)

Ah, you mean ANA inaccessible?
Hmm. Technically, yes, this might be the case.
I'll be updating the patch.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

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