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kernel, resource: check for IORESOURCE_SYSRAM in release_mem_region_adjustable 

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.

Link: http://lkml.kernel.org/r/20181127162005.15833-3-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oscar Salvador 2018-12-28 00:36:26 -08:00 committed by Linus Torvalds
parent 2c2a5af6fe
commit 65c7878413
1 changed files with 15 additions and 0 deletions
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15
kernel/resource.c
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@ -1256,6 +1256,21 @@ 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;