Messages in this thread Patch in this message | | | From | Oscar Salvador <> | Subject | [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable | Date | Mon, 15 Oct 2018 17:30:32 +0200 |
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From: Oscar Salvador <osalvador@suse.de>
This is a preparation for the next patch.
Currently, we only call release_mem_region_adjustable() in __remove_pages if the zone is not ZONE_DEVICE, because resources that belong to HMM/devm are being released by themselves with devm_release_mem_region.
Since we do not want to touch any zone/page stuff during the removing of the memory (but during the offlining), we do not want to check for the zone here. So we need another way to tell release_mem_region_adjustable() to not realease the resource in case it belongs to HMM/devm.
HMM/devm acquires/releases a resource through devm_request_mem_region/devm_release_mem_region.
These resources have the flag IORESOURCE_MEM, while resources acquired by hot-add memory path (register_memory_resource()) contain IORESOURCE_SYSTEM_RAM.
So, we can check for this flag in release_mem_region_adjustable, and if the resource does not contain such flag, we know that we are dealing with a HMM/devm resource, so we can back off.
Signed-off-by: Oscar Salvador <osalvador@suse.de> --- kernel/resource.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/kernel/resource.c b/kernel/resource.c index 81937830a42f..c45decd7d6af 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1272,6 +1272,22 @@ int release_mem_region_adjustable(struct resource *parent, continue; } + /* + * All memory regions added from memory-hotplug path + * have the flag IORESOURCE_SYSTEM_RAM. + * If the resource does not have this flag, we know that + * we are dealing with a resource coming from HMM/devm. + * HMM/devm use another mechanism to add/release a resource. + * This goes via devm_request_mem_region and + * devm_release_mem_region. + * HMM/devm take care to release their resources when they want, + * so if we are dealing with them, let us just back off here. + */ + if (!(res->flags & IORESOURCE_SYSRAM)) { + ret = 0; + break; + } + if (!(res->flags & IORESOURCE_MEM)) break; -- 2.13.6
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