[PATCH V2 1/1] nvme: fix controller ioctl through ns_head

[Minwoo Im]

In multipath case, we should consider namespace attachment with
controllers in a subsystem when we find out the live controller for the
namespace.  This patch manually reverted the commit 3557a4409701
("nvme: don't bother to look up a namespace for controller ioctls") with
few more updates to nvme_ns_head_chr_ioctl which has been newly updated.

Fixes: 3557a4409701 ("nvme: don't bother to look up a namespace for
controller ioctls")
Cc: Christoph Hellwig <hch at lst.de>
Signed-off-by: Minwoo Im <minwoo.im.dev at gmail.com>
---
 drivers/nvme/host/core.c  | 22 -------------
 drivers/nvme/host/ioctl.c | 65 ++++++++++++++++++++++++---------------
 drivers/nvme/host/nvme.h  |  1 -
 3 files changed, 41 insertions(+), 47 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2f45e8fcdd7c..f6db097ad776 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2009,28 +2009,6 @@ static const struct block_device_operations nvme_bdev_ops = {
 	.pr_ops		= &nvme_pr_ops,
 };
 
-#ifdef CONFIG_NVME_MULTIPATH
-struct nvme_ctrl *nvme_find_get_live_ctrl(struct nvme_subsystem *subsys)
-{
-	struct nvme_ctrl *ctrl;
-	int ret;
-
-	ret = mutex_lock_killable(&nvme_subsystems_lock);
-	if (ret)
-		return ERR_PTR(ret);
-	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
-		if (ctrl->state == NVME_CTRL_LIVE)
-			goto found;
-	}
-	mutex_unlock(&nvme_subsystems_lock);
-	return ERR_PTR(-EWOULDBLOCK);
-found:
-	nvme_get_ctrl(ctrl);
-	mutex_unlock(&nvme_subsystems_lock);
-	return ctrl;
-}
-#endif /* CONFIG_NVME_MULTIPATH */
-
 static int nvme_wait_ready(struct nvme_ctrl *ctrl, u64 cap, bool enabled)
 {
 	unsigned long timeout =
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 502f8e4a2a1f..9557ead02de1 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -370,41 +370,45 @@ long nvme_ns_chr_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 }
 
 #ifdef CONFIG_NVME_MULTIPATH
-static int nvme_ns_head_ctrl_ioctl(struct nvme_ns_head *head,
-		unsigned int cmd, void __user *argp)
+static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
+		void __user *argp, struct nvme_ns_head *head, int srcu_idx)
 {
-	struct nvme_ctrl *ctrl = nvme_find_get_live_ctrl(head->subsys);
+	struct nvme_ctrl *ctrl = ns->ctrl;
 	int ret;
 
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
-	ret = nvme_ctrl_ioctl(ctrl, cmd, argp);
-	nvme_put_ctrl(ctrl);
-	return ret;
-}
+	nvme_get_ctrl(ns->ctrl);
+	nvme_put_ns_from_disk(head, srcu_idx);
+	ret = nvme_ctrl_ioctl(ns->ctrl, cmd, argp);
 
-static int nvme_ns_head_ns_ioctl(struct nvme_ns_head *head,
-		unsigned int cmd, void __user *argp)
-{
-	int srcu_idx = srcu_read_lock(&head->srcu);
-	struct nvme_ns *ns = nvme_find_path(head);
-	int ret = -EWOULDBLOCK;
-
-	if (ns)
-		ret = nvme_ns_ioctl(ns, cmd, argp);
-	srcu_read_unlock(&head->srcu, srcu_idx);
+	nvme_put_ctrl(ctrl);
 	return ret;
 }
 
 int nvme_ns_head_ioctl(struct block_device *bdev, fmode_t mode,
 		unsigned int cmd, unsigned long arg)
 {
-	struct nvme_ns_head *head = bdev->bd_disk->private_data;
+	struct nvme_ns_head *head = NULL;
 	void __user *argp = (void __user *)arg;
+	struct nvme_ns *ns;
+	int srcu_idx, ret;
+
+	ns = nvme_get_ns_from_disk(bdev->bd_disk, &head, &srcu_idx);
+	if (unlikely(!ns))
+		return -EWOULDBLOCK;
 
+	/*
+	 * Handle ioctls that apply to the controller instead of the namespace
+	 * seperately and drop the ns SRCU reference early.  This avoids a
+	 * deadlock when deleting namespaces using the passthrough interface.
+	 */
 	if (is_ctrl_ioctl(cmd))
-		return nvme_ns_head_ctrl_ioctl(head, cmd, argp);
-	return nvme_ns_head_ns_ioctl(head, cmd, argp);
+		ret = nvme_ns_head_ctrl_ioctl(ns, cmd, argp, head, srcu_idx);
+	else {
+		ret = nvme_ns_ioctl(ns, cmd, argp);
+		nvme_put_ns_from_disk(head, srcu_idx);
+	}
+
+	return ret;
 }
 
 long nvme_ns_head_chr_ioctl(struct file *file, unsigned int cmd,
@@ -414,10 +418,23 @@ long nvme_ns_head_chr_ioctl(struct file *file, unsigned int cmd,
 	struct nvme_ns_head *head =
 		container_of(cdev, struct nvme_ns_head, cdev);
 	void __user *argp = (void __user *)arg;
+	struct nvme_ns *ns;
+	int srcu_idx, ret;
+
+	srcu_idx = srcu_read_lock(&head->srcu);
+	ns = nvme_find_path(head);
+	if (!ns) {
+		srcu_read_unlock(&head->srcu, srcu_idx);
+		return -EWOULDBLOCK;
+	}
 
 	if (is_ctrl_ioctl(cmd))
-		return nvme_ns_head_ctrl_ioctl(head, cmd, argp);
-	return nvme_ns_head_ns_ioctl(head, cmd, argp);
+		return nvme_ns_head_ctrl_ioctl(ns, cmd, argp, head, srcu_idx);
+
+	ret = nvme_ns_ioctl(ns, cmd, argp);
+	nvme_put_ns_from_disk(head, srcu_idx);
+
+	return ret;
 }
 #endif /* CONFIG_NVME_MULTIPATH */
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 773dde5b231d..c1e086a0bc3f 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -664,7 +664,6 @@ struct nvme_ns *nvme_get_ns_from_disk(struct gendisk *disk,
 void nvme_put_ns_from_disk(struct nvme_ns_head *head, int idx);
 bool nvme_tryget_ns_head(struct nvme_ns_head *head);
 void nvme_put_ns_head(struct nvme_ns_head *head);
-struct nvme_ctrl *nvme_find_get_live_ctrl(struct nvme_subsystem *subsys);
 int nvme_cdev_add(struct cdev *cdev, struct device *cdev_device,
 		const struct file_operations *fops, struct module *owner);
 void nvme_cdev_del(struct cdev *cdev, struct device *cdev_device);
-- 
2.27.0