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David Hildenbrand 8876cc237e drivers/base/memory: don't store phys_device in memory blocks
[ Upstream commit e9a2e48e87 ]

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
arch s390/smp: __smp_rescan_cpus() - move cpumask away from stack 2021-03-17 17:06:25 +01:00
block blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 11:38:22 +01:00
certs certs: Fix blacklist flag type confusion 2021-03-04 11:37:59 +01:00
crypto crypto: mips/poly1305 - enable for all MIPS processors 2021-03-17 17:06:10 +01:00
Documentation drivers/base/memory: don't store phys_device in memory blocks 2021-03-17 17:06:25 +01:00
drivers drivers/base/memory: don't store phys_device in memory blocks 2021-03-17 17:06:25 +01:00
fs ext4: don't try to processed freed blocks until mballoc is initialized 2021-03-17 17:06:25 +01:00
include drivers/base/memory: don't store phys_device in memory blocks 2021-03-17 17:06:25 +01:00
init kgdb: fix to kill breakpoints on initmem after boot 2021-03-04 11:38:46 +01:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel ring-buffer: Force before_stamp and write_stamp to be different on discard 2021-03-09 11:11:12 +01:00
lib kasan: fix memory corruption in kasan_bitops_tags test 2021-03-17 17:06:25 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm Revert "mm, slub: consider rest of partial list if acquire_slab() fails" 2021-03-17 17:06:13 +01:00
net net: dsa: tag_mtk: fix 802.1ad VLAN egress 2021-03-17 17:06:22 +01:00
samples samples, bpf: Add missing munmap in xdpsock 2021-03-17 17:06:12 +01:00
scripts ftrace: Have recordmcount use w8 to read relp->r_info in arm64_is_fake_mcount 2021-03-09 11:11:14 +01:00
security tomoyo: recognize kernel threads correctly 2021-03-09 11:11:15 +01:00
sound ASoC: Intel: sof_sdw: add quirk for HP Spectre x360 convertible 2021-03-11 14:17:29 +01:00
tools perf report: Fix -F for branch & mem modes 2021-03-17 17:06:17 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-02-26 10:13:01 +01:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile kbuild: clamp SUBLEVEL to 255 2021-03-17 17:06:25 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.