From: Pavel Tatashin pasha.tatashin@soleen.com
[ Upstream commit 31e4ca92a7dd4cdebd7fe1456b3b0b6ace9a816f ]
Patch series ""Hotremove" persistent memory", v6.
Recently, adding a persistent memory to be used like a regular RAM was added to Linux. This work extends this functionality to also allow hot removing persistent memory.
We (Microsoft) have an important use case for this functionality.
The requirement is for physical machines with small amount of RAM (~8G) to be able to reboot in a very short period of time (<1s). Yet, there is a userland state that is expensive to recreate (~2G).
The solution is to boot machines with 2G preserved for persistent memory.
Copy the state, and hotadd the persistent memory so machine still has all 8G available for runtime. Before reboot, offline and hotremove device-dax 2G, copy the memory that is needed to be preserved to pmem0 device, and reboot.
The series of operations look like this:
1. After boot restore /dev/pmem0 to ramdisk to be consumed by apps. and free ramdisk. 2. Convert raw pmem0 to devdax ndctl create-namespace --mode devdax --map mem -e namespace0.0 -f 3. Hotadd to System RAM echo dax0.0 > /sys/bus/dax/drivers/device_dax/unbind echo dax0.0 > /sys/bus/dax/drivers/kmem/new_id echo online_movable > /sys/devices/system/memoryXXX/state 4. Before reboot hotremove device-dax memory from System RAM echo offline > /sys/devices/system/memoryXXX/state echo dax0.0 > /sys/bus/dax/drivers/kmem/unbind 5. Create raw pmem0 device ndctl create-namespace --mode raw -e namespace0.0 -f 6. Copy the state that was stored by apps to ramdisk to pmem device 7. Do kexec reboot or reboot through firmware if firmware does not zero memory in pmem0 region (These machines have only regular volatile memory). So to have pmem0 device either memmap kernel parameter is used, or devices nodes in dtb are specified.
This patch (of 3):
When add_memory() fails, the resource and the memory should be freed.
Link: http://lkml.kernel.org/r/20190517215438.6487-2-pasha.tatashin@soleen.com Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM") Signed-off-by: Pavel Tatashin pasha.tatashin@soleen.com Reviewed-by: Dave Hansen dave.hansen@intel.com Cc: Bjorn Helgaas bhelgaas@google.com Cc: Borislav Petkov bp@suse.de Cc: Dan Williams dan.j.williams@intel.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Dave Jiang dave.jiang@intel.com Cc: David Hildenbrand david@redhat.com Cc: Fengguang Wu fengguang.wu@intel.com Cc: Huang Ying ying.huang@intel.com Cc: James Morris jmorris@namei.org Cc: Jérôme Glisse jglisse@redhat.com Cc: Keith Busch keith.busch@intel.com Cc: Michal Hocko mhocko@suse.com Cc: Ross Zwisler zwisler@kernel.org Cc: Sasha Levin sashal@kernel.org Cc: Takashi Iwai tiwai@suse.de Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Vishal Verma vishal.l.verma@intel.com Cc: Yaowei Bai baiyaowei@cmss.chinamobile.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/dax/kmem.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c index a02318c6d28a..4c0131857133 100644 --- a/drivers/dax/kmem.c +++ b/drivers/dax/kmem.c @@ -66,8 +66,11 @@ int dev_dax_kmem_probe(struct device *dev) new_res->name = dev_name(dev);
rc = add_memory(numa_node, new_res->start, resource_size(new_res)); - if (rc) + if (rc) { + release_resource(new_res); + kfree(new_res); return rc; + }
return 0; }