<feed xmlns='http://www.w3.org/2005/Atom'>
<title>kernel/linux.git/include/linux/mmzone.h, branch v5.10.257</title>
<subtitle>Linux kernel stable tree (mirror)</subtitle>
<id>https://git.radix-linux.su/kernel/linux.git/atom?h=v5.10.257</id>
<link rel='self' href='https://git.radix-linux.su/kernel/linux.git/atom?h=v5.10.257'/>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/'/>
<updated>2025-08-28T14:22:58+00:00</updated>
<entry>
<title>mm/page_alloc: detect allocation forbidden by cpuset and bail out early</title>
<updated>2025-08-28T14:22:58+00:00</updated>
<author>
<name>Feng Tang</name>
<email>feng.tang@intel.com</email>
</author>
<published>2021-11-05T20:40:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=c65b1bd0af076fa5a1da26b9cf780097b14b1543'/>
<id>urn:sha1:c65b1bd0af076fa5a1da26b9cf780097b14b1543</id>
<content type='text'>
[ Upstream commit 8ca1b5a49885f0c0c486544da46a9e0ac790831d ]

There was a report that starting an Ubuntu in docker while using cpuset
to bind it to movable nodes (a node only has movable zone, like a node
for hotplug or a Persistent Memory node in normal usage) will fail due
to memory allocation failure, and then OOM is involved and many other
innocent processes got killed.

It can be reproduced with command:

    $ docker run -it --rm --cpuset-mems 4 ubuntu:latest bash -c "grep Mems_allowed /proc/self/status"

(where node 4 is a movable node)

  runc:[2:INIT] invoked oom-killer: gfp_mask=0x500cc2(GFP_HIGHUSER|__GFP_ACCOUNT), order=0, oom_score_adj=0
  CPU: 8 PID: 8291 Comm: runc:[2:INIT] Tainted: G        W I E     5.8.2-0.g71b519a-default #1 openSUSE Tumbleweed (unreleased)
  Hardware name: Dell Inc. PowerEdge R640/0PHYDR, BIOS 2.6.4 04/09/2020
  Call Trace:
   dump_stack+0x6b/0x88
   dump_header+0x4a/0x1e2
   oom_kill_process.cold+0xb/0x10
   out_of_memory.part.0+0xaf/0x230
   out_of_memory+0x3d/0x80
   __alloc_pages_slowpath.constprop.0+0x954/0xa20
   __alloc_pages_nodemask+0x2d3/0x300
   pipe_write+0x322/0x590
   new_sync_write+0x196/0x1b0
   vfs_write+0x1c3/0x1f0
   ksys_write+0xa7/0xe0
   do_syscall_64+0x52/0xd0
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  Mem-Info:
  active_anon:392832 inactive_anon:182 isolated_anon:0
   active_file:68130 inactive_file:151527 isolated_file:0
   unevictable:2701 dirty:0 writeback:7
   slab_reclaimable:51418 slab_unreclaimable:116300
   mapped:45825 shmem:735 pagetables:2540 bounce:0
   free:159849484 free_pcp:73 free_cma:0
  Node 4 active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB all_unreclaimable? no
  Node 4 Movable free:130021408kB min:9140kB low:139160kB high:269180kB reserved_highatomic:0KB active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:130023424kB managed:130023424kB mlocked:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:292kB local_pcp:84kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 0 0
  Node 4 Movable: 1*4kB (M) 0*8kB 0*16kB 1*32kB (M) 0*64kB 0*128kB 1*256kB (M) 1*512kB (M) 1*1024kB (M) 0*2048kB 31743*4096kB (M) = 130021156kB

  oom-kill:constraint=CONSTRAINT_CPUSET,nodemask=(null),cpuset=docker-9976a269caec812c134fa317f27487ee36e1129beba7278a463dd53e5fb9997b.scope,mems_allowed=4,global_oom,task_memcg=/system.slice/containerd.service,task=containerd,pid=4100,uid=0
  Out of memory: Killed process 4100 (containerd) total-vm:4077036kB, anon-rss:51184kB, file-rss:26016kB, shmem-rss:0kB, UID:0 pgtables:676kB oom_score_adj:0
  oom_reaper: reaped process 8248 (docker), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
  oom_reaper: reaped process 2054 (node_exporter), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
  oom_reaper: reaped process 1452 (systemd-journal), now anon-rss:0kB, file-rss:8564kB, shmem-rss:4kB
  oom_reaper: reaped process 2146 (munin-node), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
  oom_reaper: reaped process 8291 (runc:[2:INIT]), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB

The reason is that in this case, the target cpuset nodes only have
movable zone, while the creation of an OS in docker sometimes needs to
allocate memory in non-movable zones (dma/dma32/normal) like
GFP_HIGHUSER, and the cpuset limit forbids the allocation, then
out-of-memory killing is involved even when normal nodes and movable
nodes both have many free memory.

The OOM killer cannot help to resolve the situation as there is no
usable memory for the request in the cpuset scope.  The only reasonable
measure to take is to fail the allocation right away and have the caller
to deal with it.

So add a check for cases like this in the slowpath of allocation, and
bail out early returning NULL for the allocation.

As page allocation is one of the hottest path in kernel, this check will
hurt all users with sane cpuset configuration, add a static branch check
and detect the abnormal config in cpuset memory binding setup so that
the extra check cost in page allocation is not paid by everyone.

[thanks to Micho Hocko and David Rientjes for suggesting not handling
 it inside OOM code, adding cpuset check, refining comments]

Link: https://lkml.kernel.org/r/1632481657-68112-1-git-send-email-feng.tang@intel.com
Signed-off-by: Feng Tang &lt;feng.tang@intel.com&gt;
Suggested-by: Michal Hocko &lt;mhocko@suse.com&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: David Rientjes &lt;rientjes@google.com&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Zefan Li &lt;lizefan.x@bytedance.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Mel Gorman &lt;mgorman@techsingularity.net&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Stable-dep-of: 65f97cc81b0a ("cgroup/cpuset: Use static_branch_enable_cpuslocked() on cpusets_insane_config_key")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>mm: prevent derefencing NULL ptr in pfn_section_valid()</title>
<updated>2024-07-18T11:05:45+00:00</updated>
<author>
<name>Waiman Long</name>
<email>longman@redhat.com</email>
</author>
<published>2024-06-26T00:16:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=0100aeb8a12d51950418e685f879cc80cb8e5982'/>
<id>urn:sha1:0100aeb8a12d51950418e685f879cc80cb8e5982</id>
<content type='text'>
[ Upstream commit 82f0b6f041fad768c28b4ad05a683065412c226e ]

Commit 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing
memory_section-&gt;usage") changed pfn_section_valid() to add a READ_ONCE()
call around "ms-&gt;usage" to fix a race with section_deactivate() where
ms-&gt;usage can be cleared.  The READ_ONCE() call, by itself, is not enough
to prevent NULL pointer dereference.  We need to check its value before
dereferencing it.

Link: https://lkml.kernel.org/r/20240626001639.1350646-1-longman@redhat.com
Fixes: 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing memory_section-&gt;usage")
Signed-off-by: Waiman Long &lt;longman@redhat.com&gt;
Cc: Charan Teja Kalla &lt;quic_charante@quicinc.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>mm/sparsemem: fix race in accessing memory_section-&gt;usage</title>
<updated>2024-02-23T07:42:00+00:00</updated>
<author>
<name>Charan Teja Kalla</name>
<email>quic_charante@quicinc.com</email>
</author>
<published>2023-10-13T13:04:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=90ad17575d26874287271127d43ef3c2af876cea'/>
<id>urn:sha1:90ad17575d26874287271127d43ef3c2af876cea</id>
<content type='text'>
[ Upstream commit 5ec8e8ea8b7783fab150cf86404fc38cb4db8800 ]

The below race is observed on a PFN which falls into the device memory
region with the system memory configuration where PFN's are such that
[ZONE_NORMAL ZONE_DEVICE ZONE_NORMAL].  Since normal zone start and end
pfn contains the device memory PFN's as well, the compaction triggered
will try on the device memory PFN's too though they end up in NOP(because
pfn_to_online_page() returns NULL for ZONE_DEVICE memory sections).  When
from other core, the section mappings are being removed for the
ZONE_DEVICE region, that the PFN in question belongs to, on which
compaction is currently being operated is resulting into the kernel crash
with CONFIG_SPASEMEM_VMEMAP enabled.  The crash logs can be seen at [1].

compact_zone()			memunmap_pages
-------------			---------------
__pageblock_pfn_to_page
   ......
 (a)pfn_valid():
     valid_section()//return true
			      (b)__remove_pages()-&gt;
				  sparse_remove_section()-&gt;
				    section_deactivate():
				    [Free the array ms-&gt;usage and set
				     ms-&gt;usage = NULL]
     pfn_section_valid()
     [Access ms-&gt;usage which
     is NULL]

NOTE: From the above it can be said that the race is reduced to between
the pfn_valid()/pfn_section_valid() and the section deactivate with
SPASEMEM_VMEMAP enabled.

The commit b943f045a9af("mm/sparse: fix kernel crash with
pfn_section_valid check") tried to address the same problem by clearing
the SECTION_HAS_MEM_MAP with the expectation of valid_section() returns
false thus ms-&gt;usage is not accessed.

Fix this issue by the below steps:

a) Clear SECTION_HAS_MEM_MAP before freeing the -&gt;usage.

b) RCU protected read side critical section will either return NULL
   when SECTION_HAS_MEM_MAP is cleared or can successfully access -&gt;usage.

c) Free the -&gt;usage with kfree_rcu() and set ms-&gt;usage = NULL.  No
   attempt will be made to access -&gt;usage after this as the
   SECTION_HAS_MEM_MAP is cleared thus valid_section() return false.

Thanks to David/Pavan for their inputs on this patch.

[1] https://lore.kernel.org/linux-mm/994410bb-89aa-d987-1f50-f514903c55aa@quicinc.com/

On Snapdragon SoC, with the mentioned memory configuration of PFN's as
[ZONE_NORMAL ZONE_DEVICE ZONE_NORMAL], we are able to see bunch of
issues daily while testing on a device farm.

For this particular issue below is the log.  Though the below log is
not directly pointing to the pfn_section_valid(){ ms-&gt;usage;}, when we
loaded this dump on T32 lauterbach tool, it is pointing.

[  540.578056] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000000
[  540.578068] Mem abort info:
[  540.578070]   ESR = 0x0000000096000005
[  540.578073]   EC = 0x25: DABT (current EL), IL = 32 bits
[  540.578077]   SET = 0, FnV = 0
[  540.578080]   EA = 0, S1PTW = 0
[  540.578082]   FSC = 0x05: level 1 translation fault
[  540.578085] Data abort info:
[  540.578086]   ISV = 0, ISS = 0x00000005
[  540.578088]   CM = 0, WnR = 0
[  540.579431] pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBSBTYPE=--)
[  540.579436] pc : __pageblock_pfn_to_page+0x6c/0x14c
[  540.579454] lr : compact_zone+0x994/0x1058
[  540.579460] sp : ffffffc03579b510
[  540.579463] x29: ffffffc03579b510 x28: 0000000000235800 x27:000000000000000c
[  540.579470] x26: 0000000000235c00 x25: 0000000000000068 x24:ffffffc03579b640
[  540.579477] x23: 0000000000000001 x22: ffffffc03579b660 x21:0000000000000000
[  540.579483] x20: 0000000000235bff x19: ffffffdebf7e3940 x18:ffffffdebf66d140
[  540.579489] x17: 00000000739ba063 x16: 00000000739ba063 x15:00000000009f4bff
[  540.579495] x14: 0000008000000000 x13: 0000000000000000 x12:0000000000000001
[  540.579501] x11: 0000000000000000 x10: 0000000000000000 x9 :ffffff897d2cd440
[  540.579507] x8 : 0000000000000000 x7 : 0000000000000000 x6 :ffffffc03579b5b4
[  540.579512] x5 : 0000000000027f25 x4 : ffffffc03579b5b8 x3 :0000000000000001
[  540.579518] x2 : ffffffdebf7e3940 x1 : 0000000000235c00 x0 :0000000000235800
[  540.579524] Call trace:
[  540.579527]  __pageblock_pfn_to_page+0x6c/0x14c
[  540.579533]  compact_zone+0x994/0x1058
[  540.579536]  try_to_compact_pages+0x128/0x378
[  540.579540]  __alloc_pages_direct_compact+0x80/0x2b0
[  540.579544]  __alloc_pages_slowpath+0x5c0/0xe10
[  540.579547]  __alloc_pages+0x250/0x2d0
[  540.579550]  __iommu_dma_alloc_noncontiguous+0x13c/0x3fc
[  540.579561]  iommu_dma_alloc+0xa0/0x320
[  540.579565]  dma_alloc_attrs+0xd4/0x108

[quic_charante@quicinc.com: use kfree_rcu() in place of synchronize_rcu(), per David]
  Link: https://lkml.kernel.org/r/1698403778-20938-1-git-send-email-quic_charante@quicinc.com
Link: https://lkml.kernel.org/r/1697202267-23600-1-git-send-email-quic_charante@quicinc.com
Fixes: f46edbd1b151 ("mm/sparsemem: add helpers track active portions of a section at boot")
Signed-off-by: Charan Teja Kalla &lt;quic_charante@quicinc.com&gt;
Cc: Aneesh Kumar K.V &lt;aneesh.kumar@linux.ibm.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: David Hildenbrand &lt;david@redhat.com&gt;
Cc: Mel Gorman &lt;mgorman@techsingularity.net&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>mm: use __pfn_to_section() instead of open coding it</title>
<updated>2024-02-23T07:42:00+00:00</updated>
<author>
<name>Rolf Eike Beer</name>
<email>eb@emlix.com</email>
</author>
<published>2021-11-05T20:38:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=74a80f8dda6a1301471ecc7c0365bdefcd6852be'/>
<id>urn:sha1:74a80f8dda6a1301471ecc7c0365bdefcd6852be</id>
<content type='text'>
[ Upstream commit f1dc0db296bd25960273649fc6ef2ecbf5aaa0e0 ]

It is defined in the same file just a few lines above.

Link: https://lkml.kernel.org/r/4598487.Rc0NezkW7i@mobilepool36.emlix.com
Signed-off-by: Rolf Eike Beer &lt;eb@emlix.com&gt;
Reviewed-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Stable-dep-of: 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing memory_section-&gt;usage")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>arm: remove CONFIG_ARCH_HAS_HOLES_MEMORYMODEL</title>
<updated>2022-05-15T18:00:09+00:00</updated>
<author>
<name>Mike Rapoport</name>
<email>rppt@linux.ibm.com</email>
</author>
<published>2020-12-15T03:09:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=9ff4a6b80642623a7eeb82f1e48feb549fcba6d9'/>
<id>urn:sha1:9ff4a6b80642623a7eeb82f1e48feb549fcba6d9</id>
<content type='text'>
commit 5e545df3292fbd3d5963c68980f1527ead2a2b3f upstream.

ARM is the only architecture that defines CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
which in turn enables memmap_valid_within() function that is intended to
verify existence  of struct page associated with a pfn when there are holes
in the memory map.

However, the ARCH_HAS_HOLES_MEMORYMODEL also enables HAVE_ARCH_PFN_VALID
and arch-specific pfn_valid() implementation that also deals with the holes
in the memory map.

The only two users of memmap_valid_within() call this function after
a call to pfn_valid() so the memmap_valid_within() check becomes redundant.

Remove CONFIG_ARCH_HAS_HOLES_MEMORYMODEL and memmap_valid_within() and rely
entirely on ARM's implementation of pfn_valid() that is now enabled
unconditionally.

Link: https://lkml.kernel.org/r/20201101170454.9567-9-rppt@kernel.org
Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Cc: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Greg Ungerer &lt;gerg@linux-m68k.org&gt;
Cc: John Paul Adrian Glaubitz &lt;glaubitz@physik.fu-berlin.de&gt;
Cc: Jonathan Corbet &lt;corbet@lwn.net&gt;
Cc: Matt Turner &lt;mattst88@gmail.com&gt;
Cc: Meelis Roos &lt;mroos@linux.ee&gt;
Cc: Michael Schmitz &lt;schmitzmic@gmail.com&gt;
Cc: Russell King &lt;linux@armlinux.org.uk&gt;
Cc: Tony Luck &lt;tony.luck@intel.com&gt;
Cc: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Fixes: 8dd559d53b3b ("arm: ioremap: don't abuse pfn_valid() to check if pfn is in RAM")
Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning</title>
<updated>2022-04-13T19:01:11+00:00</updated>
<author>
<name>Waiman Long</name>
<email>longman@redhat.com</email>
</author>
<published>2022-04-08T20:09:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=5c672073bcca537a0880257f31c6d942388df046'/>
<id>urn:sha1:5c672073bcca537a0880257f31c6d942388df046</id>
<content type='text'>
commit a431dbbc540532b7465eae4fc8b56a85a9fc7d17 upstream.

The gcc 12 compiler reports a "'mem_section' will never be NULL" warning
on the following code:

    static inline struct mem_section *__nr_to_section(unsigned long nr)
    {
    #ifdef CONFIG_SPARSEMEM_EXTREME
        if (!mem_section)
                return NULL;
    #endif
        if (!mem_section[SECTION_NR_TO_ROOT(nr)])
                return NULL;
       :

It happens with CONFIG_SPARSEMEM_EXTREME off.  The mem_section definition
is

    #ifdef CONFIG_SPARSEMEM_EXTREME
    extern struct mem_section **mem_section;
    #else
    extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
    #endif

In the !CONFIG_SPARSEMEM_EXTREME case, mem_section is a static
2-dimensional array and so the check "!mem_section[SECTION_NR_TO_ROOT(nr)]"
doesn't make sense.

Fix this warning by moving the "!mem_section[SECTION_NR_TO_ROOT(nr)]"
check up inside the CONFIG_SPARSEMEM_EXTREME block and adding an
explicit NR_SECTION_ROOTS check to make sure that there is no
out-of-bound array access.

Link: https://lkml.kernel.org/r/20220331180246.2746210-1-longman@redhat.com
Fixes: 3e347261a80b ("sparsemem extreme implementation")
Signed-off-by: Waiman Long &lt;longman@redhat.com&gt;
Reported-by: Justin Forbes &lt;jforbes@redhat.com&gt;
Cc: "Kirill A . Shutemov" &lt;kirill.shutemov@linux.intel.com&gt;
Cc: Ingo Molnar &lt;mingo@kernel.org&gt;
Cc: Rafael Aquini &lt;aquini@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>mm_zone: add function to check if managed dma zone exists</title>
<updated>2022-01-27T09:53:44+00:00</updated>
<author>
<name>Baoquan He</name>
<email>bhe@redhat.com</email>
</author>
<published>2022-01-14T22:07:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=d2e572411738a5aad67901caef8e083fb9df29fd'/>
<id>urn:sha1:d2e572411738a5aad67901caef8e083fb9df29fd</id>
<content type='text'>
commit 62b3107073646e0946bd97ff926832bafb846d17 upstream.

Patch series "Handle warning of allocation failure on DMA zone w/o
managed pages", v4.

**Problem observed:
On x86_64, when crash is triggered and entering into kdump kernel, page
allocation failure can always be seen.

 ---------------------------------
 DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
 swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 0 PID: 1 Comm: swapper/0
 Call Trace:
  dump_stack+0x7f/0xa1
  warn_alloc.cold+0x72/0xd6
  ......
  __alloc_pages+0x24d/0x2c0
  ......
  dma_atomic_pool_init+0xdb/0x176
  do_one_initcall+0x67/0x320
  ? rcu_read_lock_sched_held+0x3f/0x80
  kernel_init_freeable+0x290/0x2dc
  ? rest_init+0x24f/0x24f
  kernel_init+0xa/0x111
  ret_from_fork+0x22/0x30
 Mem-Info:
 ------------------------------------

***Root cause:
In the current kernel, it assumes that DMA zone must have managed pages
and try to request pages if CONFIG_ZONE_DMA is enabled. While this is not
always true. E.g in kdump kernel of x86_64, only low 1M is presented and
locked down at very early stage of boot, so that this low 1M won't be
added into buddy allocator to become managed pages of DMA zone. This
exception will always cause page allocation failure if page is requested
from DMA zone.

***Investigation:
This failure happens since below commit merged into linus's tree.
  1a6a9044b967 x86/setup: Remove CONFIG_X86_RESERVE_LOW and reservelow= options
  23721c8e92f7 x86/crash: Remove crash_reserve_low_1M()
  f1d4d47c5851 x86/setup: Always reserve the first 1M of RAM
  7c321eb2b843 x86/kdump: Remove the backup region handling
  6f599d84231f x86/kdump: Always reserve the low 1M when the crashkernel option is specified

Before them, on x86_64, the low 640K area will be reused by kdump kernel.
So in kdump kernel, the content of low 640K area is copied into a backup
region for dumping before jumping into kdump. Then except of those firmware
reserved region in [0, 640K], the left area will be added into buddy
allocator to become available managed pages of DMA zone.

However, after above commits applied, in kdump kernel of x86_64, the low
1M is reserved by memblock, but not released to buddy allocator. So any
later page allocation requested from DMA zone will fail.

At the beginning, if crashkernel is reserved, the low 1M need be locked
down because AMD SME encrypts memory making the old backup region
mechanims impossible when switching into kdump kernel.

Later, it was also observed that there are BIOSes corrupting memory
under 1M. To solve this, in commit f1d4d47c5851, the entire region of
low 1M is always reserved after the real mode trampoline is allocated.

Besides, recently, Intel engineer mentioned their TDX (Trusted domain
extensions) which is under development in kernel also needs to lock down
the low 1M. So we can't simply revert above commits to fix the page allocation
failure from DMA zone as someone suggested.

***Solution:
Currently, only DMA atomic pool and dma-kmalloc will initialize and
request page allocation with GFP_DMA during bootup.

So only initializ DMA atomic pool when DMA zone has available managed
pages, otherwise just skip the initialization.

For dma-kmalloc(), for the time being, let's mute the warning of
allocation failure if requesting pages from DMA zone while no manged
pages.  Meanwhile, change code to use dma_alloc_xx/dma_map_xx API to
replace kmalloc(GFP_DMA), or do not use GFP_DMA when calling kmalloc() if
not necessary.  Christoph is posting patches to fix those under
drivers/scsi/.  Finally, we can remove the need of dma-kmalloc() as people
suggested.

This patch (of 3):

In some places of the current kernel, it assumes that dma zone must have
managed pages if CONFIG_ZONE_DMA is enabled.  While this is not always
true.  E.g in kdump kernel of x86_64, only low 1M is presented and locked
down at very early stage of boot, so that there's no managed pages at all
in DMA zone.  This exception will always cause page allocation failure if
page is requested from DMA zone.

Here add function has_managed_dma() and the relevant helper functions to
check if there's DMA zone with managed pages.  It will be used in later
patches.

Link: https://lkml.kernel.org/r/20211223094435.248523-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20211223094435.248523-2-bhe@redhat.com
Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Signed-off-by: Baoquan He &lt;bhe@redhat.com&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Acked-by: John Donnelly  &lt;john.p.donnelly@oracle.com&gt;
Cc: Christoph Hellwig &lt;hch@lst.de&gt;
Cc: Christoph Lameter &lt;cl@linux.com&gt;
Cc: Hyeonggon Yoo &lt;42.hyeyoo@gmail.com&gt;
Cc: Pekka Enberg &lt;penberg@kernel.org&gt;
Cc: David Rientjes &lt;rientjes@google.com&gt;
Cc: Joonsoo Kim &lt;iamjoonsoo.kim@lge.com&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: David Laight &lt;David.Laight@ACULAB.COM&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Marek Szyprowski &lt;m.szyprowski@samsung.com&gt;
Cc: Robin Murphy &lt;robin.murphy@arm.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>mm: make zone_to_nid() and zone_set_nid() available for DISCONTIGMEM</title>
<updated>2021-08-15T12:00:25+00:00</updated>
<author>
<name>Mike Rapoport</name>
<email>rppt@linux.ibm.com</email>
</author>
<published>2021-08-11T13:41:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=eaa7feecd366577148fc17958fd708cea4874a97'/>
<id>urn:sha1:eaa7feecd366577148fc17958fd708cea4874a97</id>
<content type='text'>
Since the commit ce6ee46e0f39 ("mm/page_alloc: fix memory map
initialization for descending nodes") initialization of the memory map
relies on availability of zone_to_nid() and zone_set_nid methods to link
struct page to a node.

But in 5.10 zone_to_nid() is only defined for NUMA, but not for
DISCONTIGMEM which causes crashes on m68k systems with two memory banks.

For instance on ARAnyM with both ST-RAM and FastRAM atari_defconfig build
produces the following crash:

Unable to handle kernel access at virtual address (ptrval)
Oops: 00000000
Modules linked in:
PC: [&lt;0005fbbc&gt;] bpf_prog_alloc_no_stats+0x5c/0xba
SR: 2200  SP: (ptrval)  a2: 016daa90
d0: 0000000c    d1: 00000200    d2: 00000001    d3: 00000cc0
d4: 016d1f80    d5: 00034da6    a0: 305c2800    a1: 305c2a00
Process swapper (pid: 1, task=(ptrval))
Frame format=7 eff addr=31800000 ssw=0445 faddr=31800000
wb 1 stat/addr/data: 0000 00000000 00000000
wb 2 stat/addr/data: 0000 00000000 00000000
wb 3 stat/addr/data: 00c5 31800000 00000001
push data: 00000000 00000000 00000000 00000000
Stack from 3058fec8:
        00000dc0 00000000 004addc2 3058ff16 0005fc34 00000238 00000000 00000210
        004addc2 3058ff16 00281ae0 00000238 00000000 00000000 004addc2 004bc7ec
        004aea9e 0048b0c0 3058ff16 00460042 004ba4d2 3058ff8c 004ade6a 0000007e
        0000210e 0000007e 00000002 016d1f80 00034da6 000020b4 00000000 004b4764
        004bc7ec 00000000 004b4760 004bc7c0 004b4744 001e4cb2 00010001 016d1fe5
        016d1ff0 004994d2 003e1589 016d1f80 00412b8c 0000007e 00000001 00000001
Call Trace: [&lt;004addc2&gt;] sock_init+0x0/0xaa
 [&lt;0005fc34&gt;] bpf_prog_alloc+0x1a/0x66
 [&lt;004addc2&gt;] sock_init+0x0/0xaa
 [&lt;00281ae0&gt;] bpf_prog_create+0x2e/0x7c
 [&lt;004addc2&gt;] sock_init+0x0/0xaa
 [&lt;004aea9e&gt;] ptp_classifier_init+0x22/0x44
 [&lt;004ade6a&gt;] sock_init+0xa8/0xaa
 [&lt;0000210e&gt;] do_one_initcall+0x5a/0x150
 [&lt;00034da6&gt;] parse_args+0x0/0x208
 [&lt;000020b4&gt;] do_one_initcall+0x0/0x150
 [&lt;001e4cb2&gt;] strcpy+0x0/0x1c
 [&lt;00010001&gt;] stwotoxd+0x5/0x1c
 [&lt;004994d2&gt;] kernel_init_freeable+0x154/0x1a6
 [&lt;001e4cb2&gt;] strcpy+0x0/0x1c
 [&lt;0049951a&gt;] kernel_init_freeable+0x19c/0x1a6
 [&lt;004addc2&gt;] sock_init+0x0/0xaa
 [&lt;00321510&gt;] kernel_init+0x0/0xd8
 [&lt;00321518&gt;] kernel_init+0x8/0xd8
 [&lt;00321510&gt;] kernel_init+0x0/0xd8
 [&lt;00002890&gt;] ret_from_kernel_thread+0xc/0x14

Code: 204b 200b 4cdf 180c 4e75 700c e0aa 3682 &lt;2748&gt; 001c 214b 0140 022b
ffbf 0002 206b 001c 2008 0680 0000 0108 2140 0108 2140
Disabling lock debugging due to kernel taint
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Using CONFIG_NEED_MULTIPLE_NODES rather than CONFIG_NUMA to guard
definitions of zone_to_nid() and zone_set_nid() fixes the issue.

Reported-by: Mikael Pettersson &lt;mikpelinux@gmail.com&gt;
Fixes: ce6ee46e0f39 ("mm/page_alloc: fix memory map initialization for descending nodes")
Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Tested-by: Mikael Pettersson &lt;mikpelinux@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>mm: Remove examples from enum zone_type comment</title>
<updated>2021-03-09T10:11:14+00:00</updated>
<author>
<name>Nicolas Saenz Julienne</name>
<email>nsaenzjulienne@suse.de</email>
</author>
<published>2021-03-03T07:33:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=4d7ed9a49b0ce079af2255b0c49b0d4b5a5ceff0'/>
<id>urn:sha1:4d7ed9a49b0ce079af2255b0c49b0d4b5a5ceff0</id>
<content type='text'>
commit 04435217f96869ac3a8f055ff68c5237a60bcd7e upstream

We can't really list every setup in common code. On top of that they are
unlikely to stay true for long as things change in the arch trees
independently of this comment.

Suggested-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Nicolas Saenz Julienne &lt;nsaenzjulienne@suse.de&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Link: https://lore.kernel.org/r/20201119175400.9995-8-nsaenzjulienne@suse.de
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Jing Xiangfeng &lt;jingxiangfeng@huawei.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>include/linux/mmzone.h: remove unused early_pfn_valid()</title>
<updated>2020-10-16T18:11:19+00:00</updated>
<author>
<name>Mike Rapoport</name>
<email>rppt@linux.ibm.com</email>
</author>
<published>2020-10-16T03:10:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=1f0f8c0de09066d23760c1f5fac2cd53b32f1127'/>
<id>urn:sha1:1f0f8c0de09066d23760c1f5fac2cd53b32f1127</id>
<content type='text'>
The early_pfn_valid() macro is defined but it is never used.  Remove it.

Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Acked-by: David Hildenbrand &lt;david@redhat.com&gt;
Link: https://lkml.kernel.org/r/20200923162915.26935-1-rppt@kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
</feed>
