FAILED: patch "[PATCH] cxl/pmem: Fix nvdimm registration races" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x f57aec443c24d2e8e1f3b5b4856aea12ddda4254
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '[email protected]' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

f57aec443c24 ("cxl/pmem: Fix nvdimm registration races")
4a0079bc7aae ("nvdimm: Replace lockdep_mutex with local lock classes") 3b6c6c039707 ("nvdimm/region: Delete nd_blk_region infrastructure") 84bd3690bf54 ("nvdimm/namespace: Delete nd_namespace_blk")
fadc38a6672a ("nvdimm/namespace: Delete blk namespace consideration in shared paths") d9d290d7e659 ("nvdimm/region: Fix default alignment for small regions") 60b8f17215de ("cxl/pmem: Translate NVDIMM label commands to CXL label commands") 12f3856ad42d ("cxl/mbox: Add exclusive kernel command support")
ff56ab9e164d ("cxl/mbox: Convert 'enabled_cmds' to DECLARE_BITMAP") 4faf31b43468 ("cxl/mbox: Move mailbox and other non-PCI specific infrastructure to the core") 4cb35f1ca05a ("cxl/pci: Drop idr.h")
b64955a92929 ("cxl/mbox: Introduce the mbox_send operation")
13e7749d06b3 ("cxl/pci: Clean up cxl_mem_get_partition_info()")
99e222a5f1b6 ("cxl/pci: Make 'struct cxl_mem' device type generic") 5af96835e4da ("libnvdimm/labels: Introduce CXL labels")
540ccaa2e4dd ("libnvdimm/label: Define CXL region labels")
42e192aa9891 ("libnvdimm/labels: Introduce the concept of multi-range namespace labels") 8172db92527c ("libnvdimm/label: Add a helper for nlabel validation") d1c6e08e7503 ("libnvdimm/labels: Add uuid helpers")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f57aec443c24d2e8e1f3b5b4856aea12ddda4254 Mon Sep 17 00:00:00 2001
From: Dan Williams <[email protected]>
Date: Mon, 13 Feb 2023 17:01:05 -0800
Subject: [PATCH] cxl/pmem: Fix nvdimm registration races

A loop of the form:

while true; do modprobe cxl_pci; modprobe -r cxl_pci; done

...fails with the following crash signature:

    BUG: kernel NULL pointer dereference, address: 0000000000000040
    [..]
    RIP: 0010:cxl_internal_send_cmd+0x5/0xb0 [cxl_core]
    [..]
    Call Trace:
     <TASK>
     cxl_pmem_ctl+0x121/0x240 [cxl_pmem]
     nvdimm_get_config_data+0xd6/0x1a0 [libnvdimm]
     nd_label_data_init+0x135/0x7e0 [libnvdimm]
     nvdimm_probe+0xd6/0x1c0 [libnvdimm]
     nvdimm_bus_probe+0x7a/0x1e0 [libnvdimm]
     really_probe+0xde/0x380
     __driver_probe_device+0x78/0x170
     driver_probe_device+0x1f/0x90
     __device_attach_driver+0x85/0x110
     bus_for_each_drv+0x7d/0xc0
     __device_attach+0xb4/0x1e0
     bus_probe_device+0x9f/0xc0
     device_add+0x445/0x9c0
     nd_async_device_register+0xe/0x40 [libnvdimm]
     async_run_entry_fn+0x30/0x130

...namely that the bottom half of async nvdimm device registration runs after the CXL has already torn down the context that cxl_pmem_ctl() needs. Unlike the ACPI NFIT case that benefits from launching multiple nvdimm device registrations in parallel from those listed in the table, CXL is already marked PROBE_PREFER_ASYNCHRONOUS. So provide for a synchronous registration path to preclude this scenario.

index 08bbbac9a6d0..71cfa1fdf902 100644
@@ -76,6 +76,7 @@ static int cxl_nvdimm_probe(struct device *dev)
 		return rc;
 
 	set_bit(NDD_LABELING, &flags);
+	set_bit(NDD_REGISTER_SYNC, &flags);
 	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
 	set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask);
 	set_bit(ND_CMD_SET_CONFIG_DATA, &cmd_mask);

index b38d0355b0ac..5ad49056921b 100644
@@ -508,7 +508,7 @@ static void nd_async_device_unregister(void *d, async_cookie_t cookie)
 	put_device(dev);
 }
 
-void nd_device_register(struct device *dev)
+static void __nd_device_register(struct device *dev, bool sync)
 {
 	if (!dev)
 		return;

@@ -531,11 +531,24 @@ void nd_device_register(struct device *dev)
 	}
 	get_device(dev);
 
-	async_schedule_dev_domain(nd_async_device_register, dev,
-				  &nd_async_domain);
+	if (sync)
+		nd_async_device_register(dev, 0);
+	else
+		async_schedule_dev_domain(nd_async_device_register, dev,
+					  &nd_async_domain);
+}
+
+void nd_device_register(struct device *dev)
+{
+	__nd_device_register(dev, false);
 }
 EXPORT_SYMBOL(nd_device_register);
 
+void nd_device_register_sync(struct device *dev)
+{
+	__nd_device_register(dev, true);
+}
+
 void nd_device_unregister(struct device *dev, enum nd_async_mode mode)
 {
 	bool killed;

index 1fc081dcf631..6d3b03a9fa02 100644
@@ -624,7 +624,10 @@ struct nvdimm *__nvdimm_create(struct nvdimm_bus *nvdimm_bus,
 	nvdimm->sec.ext_flags = nvdimm_security_flags(nvdimm, NVDIMM_MASTER);
 	device_initialize(dev);
 	lockdep_set_class(&dev->mutex, &nvdimm_key);
-	nd_device_register(dev);
+	if (test_bit(NDD_REGISTER_SYNC, &flags))
+		nd_device_register_sync(dev);
+	else
+		nd_device_register(dev);
 
 	return nvdimm;
 }

index cc86ee09d7c0..845408f10655 100644
@@ -107,6 +107,7 @@ int nvdimm_bus_create_ndctl(struct nvdimm_bus *nvdimm_bus);
 void nvdimm_bus_destroy_ndctl(struct nvdimm_bus *nvdimm_bus);
 void nd_synchronize(void);
 void nd_device_register(struct device *dev);
+void nd_device_register_sync(struct device *dev);
 struct nd_label_id;
 char *nd_label_gen_id(struct nd_label_id *label_id, const uuid_t *uuid,
 		      u32 flags);

index af38252ad704..e772aae71843 100644
@@ -41,6 +41,9 @@ enum {
 	 */
 	NDD_INCOHERENT = 7,
 
+	/* dimm provider wants synchronous registration by __nvdimm_create() */
+	NDD_REGISTER_SYNC = 8,
+
 	/* need to set a limit somewhere, but yes, this is likely overkill */
 	ND_IOCTL_MAX_BUFLEN = SZ_4M,
 	ND_CMD_MAX_ELEM = 5,