From 31e4ca92a7dd4cdebd7fe1456b3b0b6ace9a816f Mon Sep 17 00:00:00 2001 From: Pavel Tatashin Date: Tue, 16 Jul 2019 16:30:27 -0700 Subject: [PATCH] device-dax: fix memory and resource leak if hotplug fails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Dave Hansen Cc: Bjorn Helgaas Cc: Borislav Petkov Cc: Dan Williams Cc: Dave Hansen Cc: Dave Jiang Cc: David Hildenbrand Cc: Fengguang Wu Cc: Huang Ying Cc: James Morris Cc: Jérôme Glisse Cc: Keith Busch Cc: Michal Hocko Cc: Ross Zwisler Cc: Sasha Levin Cc: Takashi Iwai Cc: Tom Lendacky Cc: Vishal Verma Cc: Yaowei Bai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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; }