Re: [PATCH v2] nvme: fix multipath crash when ANA desactivated

[Max Gurtovoy]

On 7/10/2019 12:29 AM, Christoph Hellwig wrote:

On Sat, Jul 06, 2019 at 01:06:44PM +0300, Max Gurtovoy wrote:

+       /* check if multipath is enabled and we have the capability */
+       if (!multipath)
+               return 0;
+       if (!ctrl->subsys || ((ctrl->subsys->cmic & (1 << 3)) != 0))

shouldn't it be:

if (!ctrl->subsys || ((ctrl->subsys->cmic & (1 << 3)) == 0))

or

if (!ctrl->subsys || !(ctrl->subsys->cmic & (1 << 3)))


Otherwise, you don't really do any initialization and return 0 in case you have 
the capability, right ?

Yes.  FYI, my idea how to fix this would be something like:

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index a9a927677970..cdb3e5baa329 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -12,11 +12,6 @@ module_param(multipath, bool, 0444);
  MODULE_PARM_DESC(multipath,
        "turn on native support for multiple controllers per subsystem");

-inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)

-{
-       return multipath && ctrl->subsys && (ctrl->subsys->cmic & (1 << 3));
-}
-
  /*
   * If multipathing is enabled we need to always use the subsystem instance
   * number for numbering our devices to avoid conflicts between subsystems that
@@ -622,7 +617,7 @@ int nvme_mpath_init(struct nvme_ctrl *ctrl, struct 
nvme_id_ctrl *id)
  {
        int error;

- if (!nvme_ctrl_use_ana(ctrl))

+       if (!multipath || !ctrl->subsys || !(ctrl->subsys->cmic & (1 << 3)))
                return 0;

ctrl->anacap = id->anacap;

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 716a876119c8..14eca76bec5c 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -485,7 +485,10 @@ extern const struct attribute_group 
*nvme_ns_id_attr_groups[];
  extern const struct block_device_operations nvme_ns_head_ops;

#ifdef CONFIG_NVME_MULTIPATH

-bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl);
+static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
+{
+       return ctrl->ana_log_buf != NULL;
+}
  void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
                        struct nvme_ctrl *ctrl, int *flags);
  void nvme_failover_req(struct request *req);

Yes this looks good.