David Hildenbrand 8876cc237e drivers/base/memory: don't store phys_device in memory blocks ... [ Upstream commit e9a2e48e8704c9d20a625c6f2357147d03ea7b97 ] No need to store the value for each and every memory block, as we can easily query the value at runtime. Reshuffle the members to optimize the memory layout. Also, let's clarify what the interface once was used for and why it's legacy nowadays. "phys_device" was used on s390x in older versions of lsmem[2]/chmem[3], back when they were still part of s390x-tools. They were later replaced by the variants in linux-utils. For example, RHEL6 and RHEL7 contain lsmem/chmem from s390-utils. RHEL8 switched to versions from util-linux on s390x [4]. "phys_device" was added with sysfs support for memory hotplug in commit 3947be1969 ("[PATCH] memory hotplug: sysfs and add/remove functions") in 2005. It always returned 0. s390x started returning something != 0 on some setups (if sclp.rzm is set by HW) in 2010 via commit 57b552ba0b ("memory hotplug/s390: set phys_device"). For s390x, it allowed for identifying which memory block devices belong to the same storage increment (RZM). Only if all memory block devices comprising a single storage increment were offline, the memory could actually be removed in the hypervisor. Since commit e5d709bb5f ("s390/memory hotplug: provide memory_block_size_bytes() function") in 2013 a memory block device spans at least one storage increment - which is why the interface isn't really helpful/used anymore (except by old lsmem/chmem tools). There were once RFC patches to make use of "phys_device" in ACPI context; however, the underlying problem could be solved using different interfaces [1]. [1] https://patchwork.kernel.org/patch/2163871/ [2] https://github.com/ibm-s390-tools/s390-tools/blob/v2.1.0/zconf/lsmem [3] https://github.com/ibm-s390-tools/s390-tools/blob/v2.1.0/zconf/chmem [4] https://bugzilla.redhat.com/show_bug.cgi?id=1504134 Link: https://lkml.kernel.org/r/20210201181347.13262-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Vaibhav Jain <vaibhav@linux.ibm.com> Cc: Tom Rix <trix@redhat.com> Cc: Geert Uytterhoeven <geert+renesas@glider.be> 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>		2021-03-17 17:06:25 +01:00
..
cma_debugfs.rst	docs: admin-guide: add a series of orphaned documents	2019-07-15 11:03:02 -03:00
concepts.rst	docs/mm: concepts.rst: remove unnecessary word	2020-07-23 14:02:58 -06:00
hugetlbpage.rst	doc/vm: fix typo in the hugetlb admin documentation	2020-10-13 18:38:33 -07:00
idle_page_tracking.rst
index.rst	docs: admin-guide/mm/index: Fix reference to nonexistent document	2020-07-23 14:21:37 -06:00
ksm.rst	Replace HTTP links with HTTPS ones: Documentation/admin-guide	2020-07-05 14:13:00 -06:00
memory-hotplug.rst	drivers/base/memory: don't store phys_device in memory blocks	2021-03-17 17:06:25 +01:00
nommu-mmap.rst	docs: move nommu-mmap.txt to admin-guide and rename to ReST	2020-06-26 11:33:35 -06:00
numa_memory_policy.rst	mmap locking API: convert mmap_sem comments	2020-06-09 09:39:14 -07:00
numaperf.rst	docs: mm: numaperf.rst Add brief description for access class 1.	2020-10-02 18:51:57 +02:00
pagemap.rst	mm: convert PG_balloon to PG_offline	2019-03-05 21:07:14 -08:00
soft-dirty.rst
transhuge.rst	doc: THP CoW fault no longer allocate THP	2020-06-26 00:27:37 -07:00
userfaultfd.rst	mmap locking API: convert mmap_sem comments	2020-06-09 09:39:14 -07:00