linux.git/mm/memory_hotplug.c, branch v5.18

Merge tag 'folio-5.18c' of git://git.infradead.org/users/willy/pagecache

2022-03-23T00:03:12+00:00

Pull folio updates from Matthew Wilcox:

 - Rewrite how munlock works to massively reduce the contention on
   i_mmap_rwsem (Hugh Dickins):

     https://lore.kernel.org/linux-mm/8e4356d-9622-a7f0-b2c-f116b5f2efea@google.com/

 - Sort out the page refcount mess for ZONE_DEVICE pages (Christoph
   Hellwig):

     https://lore.kernel.org/linux-mm/20220210072828.2930359-1-hch@lst.de/

 - Convert GUP to use folios and make pincount available for order-1
   pages. (Matthew Wilcox)

 - Convert a few more truncation functions to use folios (Matthew
   Wilcox)

 - Convert page_vma_mapped_walk to use PFNs instead of pages (Matthew
   Wilcox)

 - Convert rmap_walk to use folios (Matthew Wilcox)

 - Convert most of shrink_page_list() to use a folio (Matthew Wilcox)

 - Add support for creating large folios in readahead (Matthew Wilcox)

* tag 'folio-5.18c' of git://git.infradead.org/users/willy/pagecache: (114 commits)
  mm/damon: minor cleanup for damon_pa_young
  selftests/vm/transhuge-stress: Support file-backed PMD folios
  mm/filemap: Support VM_HUGEPAGE for file mappings
  mm/readahead: Switch to page_cache_ra_order
  mm/readahead: Align file mappings for non-DAX
  mm/readahead: Add large folio readahead
  mm: Support arbitrary THP sizes
  mm: Make large folios depend on THP
  mm: Fix READ_ONLY_THP warning
  mm/filemap: Allow large folios to be added to the page cache
  mm: Turn can_split_huge_page() into can_split_folio()
  mm/vmscan: Convert pageout() to take a folio
  mm/vmscan: Turn page_check_references() into folio_check_references()
  mm/vmscan: Account large folios correctly
  mm/vmscan: Optimise shrink_page_list for non-PMD-sized folios
  mm/vmscan: Free non-shmem folios without splitting them
  mm/rmap: Constify the rmap_walk_control argument
  mm/rmap: Convert rmap_walk() to take a folio
  mm: Turn page_anon_vma() into folio_anon_vma()
  mm/rmap: Turn page_lock_anon_vma_read() into folio_lock_anon_vma_read()
  ...

drivers/base/memory: determine and store zone for single-zone memory blocks

2022-03-22T22:57:10+00:00

test_pages_in_a_zone() is just another nasty PFN walker that can easily
stumble over ZONE_DEVICE memory ranges falling into the same memory block
as ordinary system RAM: the memmap of parts of these ranges might possibly
be uninitialized.  In fact, we observed (on an older kernel) with UBSAN:

  UBSAN: Undefined behaviour in ./include/linux/mm.h:1133:50
  index 7 is out of range for type 'zone [5]'
  CPU: 121 PID: 35603 Comm: read_all Kdump: loaded Tainted: [...]
  Hardware name: Dell Inc. PowerEdge R7425/08V001, BIOS 1.12.2 11/15/2019
  Call Trace:
   dump_stack+0x9a/0xf0
   ubsan_epilogue+0x9/0x7a
   __ubsan_handle_out_of_bounds+0x13a/0x181
   test_pages_in_a_zone+0x3c4/0x500
   show_valid_zones+0x1fa/0x380
   dev_attr_show+0x43/0xb0
   sysfs_kf_seq_show+0x1c5/0x440
   seq_read+0x49d/0x1190
   vfs_read+0xff/0x300
   ksys_read+0xb8/0x170
   do_syscall_64+0xa5/0x4b0
   entry_SYSCALL_64_after_hwframe+0x6a/0xdf
  RIP: 0033:0x7f01f4439b52

We seem to stumble over a memmap that contains a garbage zone id.  While
we could try inserting pfn_to_online_page() calls, it will just make
memory offlining slower, because we use test_pages_in_a_zone() to make
sure we're offlining pages that all belong to the same zone.

Let's just get rid of this PFN walker and determine the single zone of a
memory block -- if any -- for early memory blocks during boot.  For memory
onlining, we know the single zone already.  Let's avoid any additional
memmap scanning and just rely on the zone information available during
boot.

For memory hot(un)plug, we only really care about memory blocks that:
* span a single zone (and, thereby, a single node)
* are completely System RAM (IOW, no holes, no ZONE_DEVICE)
If one of these conditions is not met, we reject memory offlining.
Hotplugged memory blocks (starting out offline), always meet both
conditions.

There are three scenarios to handle:

(1) Memory hot(un)plug

A memory block with zone == NULL cannot be offlined, corresponding to
our previous test_pages_in_a_zone() check.

After successful memory onlining/offlining, we simply set the zone
accordingly.
* Memory onlining: set the zone we just used for onlining
* Memory offlining: set zone = NULL

So a hotplugged memory block starts with zone = NULL. Once memory
onlining is done, we set the proper zone.

(2) Boot memory with !CONFIG_NUMA

We know that there is just a single pgdat, so we simply scan all zones
of that pgdat for an intersection with our memory block PFN range when
adding the memory block. If more than one zone intersects (e.g., DMA and
DMA32 on x86 for the first memory block) we set zone = NULL and
consequently mimic what test_pages_in_a_zone() used to do.

(3) Boot memory with CONFIG_NUMA

At the point in time we create the memory block devices during boot, we
don't know yet which nodes *actually* span a memory block. While we could
scan all zones of all nodes for intersections, overlapping nodes complicate
the situation and scanning all nodes is possibly expensive. But that
problem has already been solved by the code that sets the node of a memory
block and creates the link in the sysfs --
do_register_memory_block_under_node().

So, we hook into the code that sets the node id for a memory block. If
we already have a different node id set for the memory block, we know
that multiple nodes *actually* have PFNs falling into our memory block:
we set zone = NULL and consequently mimic what test_pages_in_a_zone() used
to do. If there is no node id set, we do the same as (2) for the given
node.

Note that the call order in driver_init() is:
-> memory_dev_init(): create memory block devices
-> node_dev_init(): link memory block devices to the node and set the
		    node id

So in summary, we detect if there is a single zone responsible for this
memory block and we consequently store the zone in that case in the
memory block, updating it during memory onlining/offlining.

Link: https://lkml.kernel.org/r/20220210184359.235565-3-david@redhat.com
Signed-off-by: David Hildenbrand 
Reported-by: Rafael Parra 
Reviewed-by: Oscar Salvador 
Cc: "Rafael J. Wysocki" 
Cc: Greg Kroah-Hartman 
Cc: Michal Hocko 
Cc: Rafael Parra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

drivers/base/node: rename link_mem_sections() to register_memory_block_under_node()

2022-03-22T22:57:10+00:00

Patch series "drivers/base/memory: determine and store zone for single-zone memory blocks", v2.

I remember talking to Michal in the past about removing
test_pages_in_a_zone(), which we use for:
* verifying that a memory block we intend to offline is really only managed
  by a single zone. We don't support offlining of memory blocks that are
  managed by multiple zones (e.g., multiple nodes, DMA and DMA32)
* exposing that zone to user space via
  /sys/devices/system/memory/memory*/valid_zones

Now that I identified some more cases where test_pages_in_a_zone() might
go wrong, and we received an UBSAN report (see patch #3), let's get rid of
this PFN walker.

So instead of detecting the zone at runtime with test_pages_in_a_zone() by
scanning the memmap, let's determine and remember for each memory block if
it's managed by a single zone.  The stored zone can then be used for the
above two cases, avoiding a manual lookup using test_pages_in_a_zone().

This avoids eventually stumbling over uninitialized memmaps in corner
cases, especially when ZONE_DEVICE ranges partly fall into memory block
(that are responsible for managing System RAM).

Handling memory onlining is easy, because we online to exactly one zone.
Handling boot memory is more tricky, because we want to avoid scanning all
zones of all nodes to detect possible zones that overlap with the physical
memory region of interest.  Fortunately, we already have code that
determines the applicable nodes for a memory block, to create sysfs links
-- we'll hook into that.

Patch #1 is a simple cleanup I had laying around for a longer time.
Patch #2 contains the main logic to remove test_pages_in_a_zone() and
further details.

[1] https://lkml.kernel.org/r/20220128144540.153902-1-david@redhat.com
[2] https://lkml.kernel.org/r/20220203105212.30385-1-david@redhat.com

This patch (of 2):

Let's adjust the stale terminology, making it match
unregister_memory_block_under_nodes() and
do_register_memory_block_under_node().  We're dealing with memory block
devices, which span 1..X memory sections.

Link: https://lkml.kernel.org/r/20220210184359.235565-1-david@redhat.com
Link: https://lkml.kernel.org/r/20220210184359.235565-2-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Oscar Salvador 
Cc: Greg Kroah-Hartman 
Cc: Michal Hocko 
Cc: "Rafael J. Wysocki" 
Cc: Rafael Parra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: fix misplaced comment in offline_pages

2022-03-22T22:57:10+00:00

It's misplaced since commit 7960509329c2 ("mm, memory_hotplug: print
reason for the offlining failure").  Move it to the right place.

Link: https://lkml.kernel.org/r/20220207133643.23427-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: clean up try_offline_node

2022-03-22T22:57:10+00:00

We can use helper macro node_spanned_pages to check whether node spans
pages.  And we can change the parameter of check_cpu_on_node to nid as
that's what it really cares.  Thus we can further get rid of the local
variable pgdat and improve the readability a bit.

Link: https://lkml.kernel.org/r/20220207133643.23427-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: avoid calling zone_intersects() for ZONE_NORMAL

2022-03-22T22:57:10+00:00

If zid reaches ZONE_NORMAL, the caller will always get the NORMAL zone no
matter what zone_intersects() returns.  So we can save some possible cpu
cycles by avoid calling zone_intersects() for ZONE_NORMAL.

Link: https://lkml.kernel.org/r/20220207133643.23427-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: remove obsolete comment of __add_pages

2022-03-22T22:57:10+00:00

Patch series "A few cleanup patches around memory_hotplug".

This series contains a few patches to fix obsolete and misplaced comments,
clean up the try_offline_node function and so on.

This patch (of 4):

Since commit f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded
memory to zones until online"), there is no need to pass in the zone.

[akpm@linux-foundation.org: remove the comment altogether, per David]

Link: https://lkml.kernel.org/r/20220207133643.23427-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220207133643.23427-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Cc: David Hildenbrand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memory_hotplug: reorganize new pgdat initialization

2022-03-22T22:57:10+00:00

When a !node_online node is brought up it needs a hotplug specific
initialization because the node could be either uninitialized yet or it
could have been recycled after previous hotremove.  hotadd_init_pgdat is
responsible for that.

Internal pgdat state is initialized at two places currently
	- hotadd_init_pgdat
	- free_area_init_core_hotplug

There is no real clear cut what should go where but this patch's chosen to
move the whole internal state initialization into
free_area_init_core_hotplug.  hotadd_init_pgdat is still responsible to
pull all the parts together - most notably to initialize zonelists because
those depend on the overall topology.

This patch doesn't introduce any functional change.

Link: https://lkml.kernel.org/r/20220127085305.20890-5-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Acked-by: Rafael Aquini 
Acked-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Cc: Alexey Makhalov 
Cc: Christoph Lameter 
Cc: Dennis Zhou 
Cc: Eric Dumazet 
Cc: Mike Rapoport 
Cc: Nico Pache 
Cc: Tejun Heo 
Cc: Wei Yang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memory_hotplug: drop arch_free_nodedata

2022-03-22T22:57:10+00:00

Prior to "mm: handle uninitialized numa nodes gracefully" memory hotplug
used to allocate pgdat when memory has been added to a node
(hotadd_init_pgdat) arch_free_nodedata has been only used in the failure
path because once the pgdat is exported (to be visible by NODA_DATA(nid))
it cannot really be freed because there is no synchronization available
for that.

pgdat is allocated for each possible nodes now so the memory hotplug
doesn't need to do the ever use arch_free_nodedata so drop it.

This patch doesn't introduce any functional change.

Link: https://lkml.kernel.org/r/20220127085305.20890-4-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Acked-by: Rafael Aquini 
Acked-by: David Hildenbrand 
Acked-by: Mike Rapoport 
Reviewed-by: Oscar Salvador 
Cc: Alexey Makhalov 
Cc: Christoph Lameter 
Cc: Dennis Zhou 
Cc: Eric Dumazet 
Cc: Nico Pache 
Cc: Tejun Heo 
Cc: Wei Yang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: handle uninitialized numa nodes gracefully

2022-03-22T22:57:10+00:00

We have had several reports [1][2][3] that page allocator blows up when an
allocation from a possible node is requested.  The underlying reason is
that NODE_DATA for the specific node is not allocated.

NUMA specific initialization is arch specific and it can vary a lot.  E.g.
x86 tries to initialize all nodes that have some cpu affinity (see
init_cpu_to_node) but this can be insufficient because the node might be
cpuless for example.

One way to address this problem would be to check for !node_online nodes
when trying to get a zonelist and silently fall back to another node.
That is unfortunately adding a branch into allocator hot path and it
doesn't handle any other potential NODE_DATA users.

This patch takes a different approach (following a lead of [3]) and it pre
allocates pgdat for all possible nodes in an arch indipendent code -
free_area_init.  All uninitialized nodes are treated as memoryless nodes.
node_state of the node is not changed because that would lead to other
side effects - e.g.  sysfs representation of such a node and from past
discussions [4] it is known that some tools might have problems digesting
that.

Newly allocated pgdat only gets a minimal initialization and the rest of
the work is expected to be done by the memory hotplug - hotadd_new_pgdat
(renamed to hotadd_init_pgdat).

generic_alloc_nodedata is changed to use the memblock allocator because
neither page nor slab allocators are available at the stage when all
pgdats are allocated.  Hotplug doesn't allocate pgdat anymore so we can
use the early boot allocator.  The only arch specific implementation is
ia64 and that is changed to use the early allocator as well.

[1] http://lkml.kernel.org/r/20211101201312.11589-1-amakhalov@vmware.com
[2] http://lkml.kernel.org/r/20211207224013.880775-1-npache@redhat.com
[3] http://lkml.kernel.org/r/20190114082416.30939-1-mhocko@kernel.org
[4] http://lkml.kernel.org/r/20200428093836.27190-1-srikar@linux.vnet.ibm.com

[akpm@linux-foundation.org: replace comment, per Mike]

Link: https://lkml.kernel.org/r/Yfe7RBeLCijnWBON@dhcp22.suse.cz
Reported-by: Alexey Makhalov 
Tested-by: Alexey Makhalov 
Reported-by: Nico Pache 
Acked-by: Rafael Aquini 
Tested-by: Rafael Aquini 
Acked-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Acked-by: Mike Rapoport 
Signed-off-by: Michal Hocko 
Cc: Christoph Lameter 
Cc: Dennis Zhou 
Cc: Eric Dumazet 
Cc: Tejun Heo 
Cc: Wei Yang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds