linux.git/Documentation/admin-guide/mm, branch v5.14

userfaultfd/shmem: advertise shmem minor fault support

2021-07-01T03:47:27+00:00

Now that the feature is fully implemented (the faulting path hooks exist
so userspace is notified, and the ioctl to resolve such faults is
available), advertise this as a supported feature.

Link: https://lkml.kernel.org/r/20210503180737.2487560-6-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Acked-by: Hugh Dickins 
Acked-by: Peter Xu 
Cc: Alexander Viro 
Cc: Andrea Arcangeli 
Cc: Brian Geffon 
Cc: "Dr . David Alan Gilbert" 
Cc: Jerome Glisse 
Cc: Joe Perches 
Cc: Kirill A. Shutemov 
Cc: Lokesh Gidra 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Mina Almasry 
Cc: Oliver Upton 
Cc: Shaohua Li 
Cc: Shuah Khan 
Cc: Stephen Rothwell 
Cc: Wang Qing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/pagemap: export uffd-wp protection information

2021-07-01T03:47:27+00:00

Export the PTE/PMD status of uffd-wp to pagemap too.

Link: https://lkml.kernel.org/r/20210428225030.9708-6-peterx@redhat.com
Signed-off-by: Peter Xu 
Cc: Alexander Viro 
Cc: Andrea Arcangeli 
Cc: Axel Rasmussen 
Cc: Brian Geffon 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: Joe Perches 
Cc: Kirill A. Shutemov 
Cc: Lokesh Gidra 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Mina Almasry 
Cc: Oliver Upton 
Cc: Shaohua Li 
Cc: Shuah Khan 
Cc: Stephen Rothwell 
Cc: Wang Qing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap

2021-07-01T03:47:25+00:00

Add a kernel parameter hugetlb_free_vmemmap to enable the feature of
freeing unused vmemmap pages associated with each hugetlb page on boot.

We disable PMD mapping of vmemmap pages for x86-64 arch when this feature
is enabled.  Because vmemmap_remap_free() depends on vmemmap being base
page mapped.

Link: https://lkml.kernel.org/r/20210510030027.56044-8-songmuchun@bytedance.com
Signed-off-by: Muchun Song 
Reviewed-by: Oscar Salvador 
Reviewed-by: Barry Song 
Reviewed-by: Miaohe Lin 
Tested-by: Chen Huang 
Tested-by: Bodeddula Balasubramaniam 
Reviewed-by: Mike Kravetz 
Cc: Alexander Viro 
Cc: Andy Lutomirski 
Cc: Anshuman Khandual 
Cc: Balbir Singh 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: David Hildenbrand 
Cc: David Rientjes 
Cc: HORIGUCHI NAOYA 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Joao Martins 
Cc: Joerg Roedel 
Cc: Jonathan Corbet 
Cc: Matthew Wilcox 
Cc: Michal Hocko 
Cc: Mina Almasry 
Cc: Oliver Neukum 
Cc: Paul E. McKenney 
Cc: Pawan Gupta 
Cc: Peter Zijlstra 
Cc: Randy Dunlap 
Cc: Thomas Gleixner 
Cc: Xiongchun Duan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page

2021-07-01T03:47:25+00:00

When we free a HugeTLB page to the buddy allocator, we need to allocate
the vmemmap pages associated with it.  However, we may not be able to
allocate the vmemmap pages when the system is under memory pressure.  In
this case, we just refuse to free the HugeTLB page.  This changes behavior
in some corner cases as listed below:

 1) Failing to free a huge page triggered by the user (decrease nr_pages).

    User needs to try again later.

 2) Failing to free a surplus huge page when freed by the application.

    Try again later when freeing a huge page next time.

 3) Failing to dissolve a free huge page on ZONE_MOVABLE via
    offline_pages().

    This can happen when we have plenty of ZONE_MOVABLE memory, but
    not enough kernel memory to allocate vmemmmap pages.  We may even
    be able to migrate huge page contents, but will not be able to
    dissolve the source huge page.  This will prevent an offline
    operation and is unfortunate as memory offlining is expected to
    succeed on movable zones.  Users that depend on memory hotplug
    to succeed for movable zones should carefully consider whether the
    memory savings gained from this feature are worth the risk of
    possibly not being able to offline memory in certain situations.

 4) Failing to dissolve a huge page on CMA/ZONE_MOVABLE via
    alloc_contig_range() - once we have that handling in place. Mainly
    affects CMA and virtio-mem.

    Similar to 3). virito-mem will handle migration errors gracefully.
    CMA might be able to fallback on other free areas within the CMA
    region.

Vmemmap pages are allocated from the page freeing context.  In order for
those allocations to be not disruptive (e.g.  trigger oom killer)
__GFP_NORETRY is used.  hugetlb_lock is dropped for the allocation because
a non sleeping allocation would be too fragile and it could fail too
easily under memory pressure.  GFP_ATOMIC or other modes to access memory
reserves is not used because we want to prevent consuming reserves under
heavy hugetlb freeing.

[mike.kravetz@oracle.com: fix dissolve_free_huge_page use of tail/head page]
  Link: https://lkml.kernel.org/r/20210527231225.226987-1-mike.kravetz@oracle.com
[willy@infradead.org: fix alloc_vmemmap_page_list documentation warning]
  Link: https://lkml.kernel.org/r/20210615200242.1716568-6-willy@infradead.org

Link: https://lkml.kernel.org/r/20210510030027.56044-7-songmuchun@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Mike Kravetz 
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Mike Kravetz 
Reviewed-by: Oscar Salvador 
Cc: Alexander Viro 
Cc: Andy Lutomirski 
Cc: Anshuman Khandual 
Cc: Balbir Singh 
Cc: Barry Song 
Cc: Bodeddula Balasubramaniam 
Cc: Borislav Petkov 
Cc: Chen Huang 
Cc: Dave Hansen 
Cc: David Hildenbrand 
Cc: David Rientjes 
Cc: HORIGUCHI NAOYA 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Joao Martins 
Cc: Joerg Roedel 
Cc: Jonathan Corbet 
Cc: Matthew Wilcox 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mina Almasry 
Cc: Oliver Neukum 
Cc: Paul E. McKenney 
Cc: Pawan Gupta 
Cc: Peter Zijlstra 
Cc: Randy Dunlap 
Cc: Thomas Gleixner 
Cc: Xiongchun Duan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning

2021-05-05T18:27:26+00:00

Document the special handling of page pinning when ZONE_MOVABLE present.

Link: https://lkml.kernel.org/r/20210215161349.246722-11-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin 
Suggested-by: David Hildenbrand 
Acked-by: Michal Hocko 
Cc: Dan Williams 
Cc: David Rientjes 
Cc: Ingo Molnar 
Cc: Ira Weiny 
Cc: James Morris 
Cc: Jason Gunthorpe 
Cc: Jason Gunthorpe 
Cc: John Hubbard 
Cc: Joonsoo Kim 
Cc: Matthew Wilcox 
Cc: Mel Gorman 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Oscar Salvador 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Steven Rostedt (VMware) 
Cc: Tyler Hicks 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd: update documentation to describe minor fault handling

2021-05-05T18:27:23+00:00

Reword / reorganize things a little bit into "lists", so new features /
modes / ioctls can sort of just be appended.

Describe how UFFDIO_REGISTER_MODE_MINOR and UFFDIO_CONTINUE can be used to
intercept and resolve minor faults.  Make it clear that COPY and ZEROPAGE
are used for MISSING faults, whereas CONTINUE is used for MINOR faults.

Link: https://lkml.kernel.org/r/20210301222728.176417-6-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Reviewed-by: Peter Xu 
Cc: Adam Ruprecht 
Cc: Alexander Viro 
Cc: Alexey Dobriyan 
Cc: Andrea Arcangeli 
Cc: Anshuman Khandual 
Cc: Cannon Matthews 
Cc: Catalin Marinas 
Cc: Chinwen Chang 
Cc: David Rientjes 
Cc: "Dr . David Alan Gilbert" 
Cc: Huang Ying 
Cc: Ingo Molnar 
Cc: Jann Horn 
Cc: Jerome Glisse 
Cc: Kirill A. Shutemov 
Cc: Lokesh Gidra 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Michael Ellerman 
Cc: "Michal Koutn" 
Cc: Michel Lespinasse 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Mina Almasry 
Cc: Nicholas Piggin 
Cc: Oliver Upton 
Cc: Shaohua Li 
Cc: Shawn Anastasio 
Cc: Steven Price 
Cc: Steven Rostedt 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page_alloc: combine __alloc_pages and __alloc_pages_nodemask

2021-04-30T18:20:42+00:00

There are only two callers of __alloc_pages() so prune the thicket of
alloc_page variants by combining the two functions together.  Current
callers of __alloc_pages() simply add an extra 'NULL' parameter and
current callers of __alloc_pages_nodemask() call __alloc_pages() instead.

Link: https://lkml.kernel.org/r/20210225150642.2582252-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Acked-by: Vlastimil Babka 
Acked-by: Michal Hocko 
Cc: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation: Add leading slash to some paths

2021-03-31T19:49:19+00:00

Change multiple sys/xyz to /sys/xyz

Signed-off-by: Mark O'Donovan 
Link: https://lore.kernel.org/r/20210328152837.73347-1-shiftee@posteo.net
Signed-off-by: Jonathan Corbet

Documentation: sysfs/memory: clarify some memory block device properties

2021-02-26T17:41:00+00:00

In commit 53cdc1cb29e8 ("drivers/base/memory.c: indicate all memory blocks
as removable") we changed the output of the "removable" property of memory
devices to return "1" if and only if the kernel supports memory offlining.

Let's update documentation, stating that the interface is legacy.  Also
update documentation of the "state" property and "valid_zones" properties.

Link: https://lkml.kernel.org/r/20210201181347.13262-3-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Michal Hocko 
Reviewed-by: Oscar Salvador 
Cc: Dave Hansen 
Cc: Jonathan Corbet 
Cc: David Hildenbrand 
Cc: Greg Kroah-Hartman 
Cc: Jonathan Cameron 
Cc: Ilya Dryomov 
Cc: Mauro Carvalho Chehab 
Cc: Geert Uytterhoeven 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

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

2021-02-26T17:41:00+00:00

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
3947be1969a9 ("[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 57b552ba0b2f ("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 e5d709bb5fb7 ("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 
Acked-by: Michal Hocko 
Reviewed-by: Oscar Salvador 
Cc: Dave Hansen 
Cc: Greg Kroah-Hartman 
Cc: Gerald Schaefer 
Cc: Jonathan Corbet 
Cc: "Rafael J. Wysocki" 
Cc: Mauro Carvalho Chehab 
Cc: Ilya Dryomov 
Cc: Vaibhav Jain 
Cc: Tom Rix 
Cc: Geert Uytterhoeven 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds