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    Subject[PATCH 4.15 30/52] nvme: fix subsystem multiple controllers support check
    Date
    4.15-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Israel Rukshin <israelr@mellanox.com>

    commit b837b28394fb76993c28bb242db7061ee0417da6 upstream.

    There is a problem when another module (e.g. nvmet) takes a reference on
    the nvme block device and the physical nvme drive is removed. In that
    case nvme_free_ctrl() will not be called and the controller state will be
    "deleting" or "dead" unless nvmet module releases the block device.
    Later on, the same nvme drive probes back and nvme_init_subsystem() will
    be called and fail due to duplicate subnqn (if the nvme device doesn't
    support subsystem with multiple controllers). This will cause a probe
    failure. This commit changes the check of multiple controllers support
    at nvme_init_subsystem() by not counting all the controllers at "dead" or
    "deleting" state (this is safe because controllers at this state will
    never be active again).

    Fixes: ab9e00cc72fa ("nvme: track subsystems")
    Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
    Signed-off-by: Israel Rukshin <israelr@mellanox.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Keith Busch <keith.busch@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/nvme/host/core.c | 18 +++++++++++++++++-
    1 file changed, 17 insertions(+), 1 deletion(-)

    --- a/drivers/nvme/host/core.c
    +++ b/drivers/nvme/host/core.c
    @@ -2052,6 +2052,22 @@ static const struct attribute_group *nvm
    NULL,
    };

    +static int nvme_active_ctrls(struct nvme_subsystem *subsys)
    +{
    + int count = 0;
    + struct nvme_ctrl *ctrl;
    +
    + mutex_lock(&subsys->lock);
    + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
    + if (ctrl->state != NVME_CTRL_DELETING &&
    + ctrl->state != NVME_CTRL_DEAD)
    + count++;
    + }
    + mutex_unlock(&subsys->lock);
    +
    + return count;
    +}
    +
    static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
    {
    struct nvme_subsystem *subsys, *found;
    @@ -2090,7 +2106,7 @@ static int nvme_init_subsystem(struct nv
    * Verify that the subsystem actually supports multiple
    * controllers, else bail out.
    */
    - if (!(id->cmic & (1 << 1))) {
    + if (nvme_active_ctrls(found) && !(id->cmic & (1 << 1))) {
    dev_err(ctrl->device,
    "ignoring ctrl due to duplicate subnqn (%s).\n",
    found->subnqn);

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