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drivers/base/memory: don't store phys_device in memory blocks

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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>
This commit is contained in:
David Hildenbrand 2021-02-25 17:17:24 -08:00 committed by Linus Torvalds
parent 6c922cf751
commit e9a2e48e87
4 changed files with 15 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
Documentation/ABI/testing/sysfs-devices-memory
View file

@ -26,8 +26,9 @@ Date: September 2008
Contact: Badari Pulavarty <pbadari@us.ibm.com>
Description:
The file /sys/devices/system/memory/memoryX/phys_device
is read-only and is designed to show the name of physical
memory device. Implementation is currently incomplete.
is read-only; it is a legacy interface only ever used on s390x
to expose the covered storage increment.
Users: Legacy s390-tools lsmem/chmem
What: /sys/devices/system/memory/memoryX/phys_index
Date: September 2008

4
Documentation/admin-guide/mm/memory-hotplug.rst
View file

@ -160,8 +160,8 @@ Under each memory block, you can see 5 files:
"online_movable", "online", "offline" command
which will be performed on all sections in the block.
``phys_device`` read-only: designed to show the name of physical memory
device. This is not well implemented now.
``phys_device`` read-only: legacy interface only ever used on s390x to
expose the covered storage increment.
``removable`` read-only: contains an integer value indicating
whether the memory block is removable or not
removable. A value of 1 indicates that the memory

25
drivers/base/memory.c
View file

@ -290,20 +290,20 @@ static ssize_t state_store(struct device *dev, struct device_attribute *attr,
}
/*
* phys_device is a bad name for this. What I really want
* is a way to differentiate between memory ranges that
* are part of physical devices that constitute
* a complete removable unit or fru.
* i.e. do these ranges belong to the same physical device,
* s.t. if I offline all of these sections I can then
* remove the physical device?
* Legacy interface that we cannot remove: s390x exposes the storage increment
* covered by a memory block, allowing for identifying which memory blocks
* comprise a storage increment. Since a memory block spans complete
* storage increments nowadays, this interface is basically unused. Other
* archs never exposed != 0.
*/
static ssize_t phys_device_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct memory_block *mem = to_memory_block(dev);
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
return sysfs_emit(buf, "%d\n", mem->phys_device);
return sysfs_emit(buf, "%d\n",
arch_get_memory_phys_device(start_pfn));
}
#ifdef CONFIG_MEMORY_HOTREMOVE
@ -488,11 +488,7 @@ static DEVICE_ATTR_WO(soft_offline_page);
static DEVICE_ATTR_WO(hard_offline_page);
#endif
/*
* Note that phys_device is optional. It is here to allow for
* differentiation between which *physical* devices each
* section belongs to...
*/
/* See phys_device_show(). */
int __weak arch_get_memory_phys_device(unsigned long start_pfn)
{
return 0;
@ -574,7 +570,6 @@ int register_memory(struct memory_block *memory)
static int init_memory_block(unsigned long block_id, unsigned long state)
{
struct memory_block *mem;
unsigned long start_pfn;
int ret = 0;
mem = find_memory_block_by_id(block_id);
@ -588,8 +583,6 @@ static int init_memory_block(unsigned long block_id, unsigned long state)
mem->start_section_nr = block_id * sections_per_block;
mem->state = state;
start_pfn = section_nr_to_pfn(mem->start_section_nr);
mem->phys_device = arch_get_memory_phys_device(start_pfn);
mem->nid = NUMA_NO_NODE;
ret = register_memory(mem);

3
include/linux/memory.h
View file

@ -27,9 +27,8 @@ struct memory_block {
unsigned long start_section_nr;
unsigned long state; /* serialized by the dev->lock */
int online_type; /* for passing data to online routine */
int phys_device; /* to which fru does this belong? */
struct device dev;
int nid; /* NID for this memory block */
struct device dev;
};
int arch_get_memory_phys_device(unsigned long start_pfn);