linux.git/mm, branch v5.1-rc4 Linux kernel source tree mm/util.c: fix strndup_user() comment 2019-04-06T02:02:31+00:00 Andrew Morton akpm@linux-foundation.org 2019-04-06T01:39:34+00:00 e91455217d8c7b128c158432869f6e697283f3ec The kerneldoc misdescribes strndup_user()'s return value. Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Timur Tabi <timur@freescale.com> Cc: Mihai Caraman <mihai.caraman@freescale.com> Cc: Kumar Gala <galak@kernel.crashing.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
The kerneldoc misdescribes strndup_user()'s return value.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Timur Tabi <timur@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: writeback: use exact memcg dirty counts 2019-04-06T02:02:31+00:00 Greg Thelen gthelen@google.com 2019-04-06T01:39:18+00:00 0b3d6e6f2dd0a7b697b1aa8c167265908940624b Since commit a983b5ebee57 ("mm: memcontrol: fix excessive complexity in memory.stat reporting") memcg dirty and writeback counters are managed as: 1) per-memcg per-cpu values in range of [-32..32] 2) per-memcg atomic counter When a per-cpu counter cannot fit in [-32..32] it's flushed to the atomic. Stat readers only check the atomic. Thus readers such as balance_dirty_pages() may see a nontrivial error margin: 32 pages per cpu. Assuming 100 cpus: 4k x86 page_size: 13 MiB error per memcg 64k ppc page_size: 200 MiB error per memcg Considering that dirty+writeback are used together for some decisions the errors double. This inaccuracy can lead to undeserved oom kills. One nasty case is when all per-cpu counters hold positive values offsetting an atomic negative value (i.e. per_cpu[*]=32, atomic=n_cpu*-32). balance_dirty_pages() only consults the atomic and does not consider throttling the next n_cpu*32 dirty pages. If the file_lru is in the 13..200 MiB range then there's absolutely no dirty throttling, which burdens vmscan with only dirty+writeback pages thus resorting to oom kill. It could be argued that tiny containers are not supported, but it's more subtle. It's the amount the space available for file lru that matters. If a container has memory.max-200MiB of non reclaimable memory, then it will also suffer such oom kills on a 100 cpu machine. The following test reliably ooms without this patch. This patch avoids oom kills. $ cat test mount -t cgroup2 none /dev/cgroup cd /dev/cgroup echo +io +memory > cgroup.subtree_control mkdir test cd test echo 10M > memory.max (echo $BASHPID > cgroup.procs && exec /memcg-writeback-stress /foo) (echo $BASHPID > cgroup.procs && exec dd if=/dev/zero of=/foo bs=2M count=100) $ cat memcg-writeback-stress.c /* * Dirty pages from all but one cpu. * Clean pages from the non dirtying cpu. * This is to stress per cpu counter imbalance. * On a 100 cpu machine: * - per memcg per cpu dirty count is 32 pages for each of 99 cpus * - per memcg atomic is -99*32 pages * - thus the complete dirty limit: sum of all counters 0 * - balance_dirty_pages() only sees atomic count -99*32 pages, which * it max()s to 0. * - So a workload can dirty -99*32 pages before balance_dirty_pages() * cares. */ #define _GNU_SOURCE #include <err.h> #include <fcntl.h> #include <sched.h> #include <stdlib.h> #include <stdio.h> #include <sys/stat.h> #include <sys/sysinfo.h> #include <sys/types.h> #include <unistd.h> static char *buf; static int bufSize; static void set_affinity(int cpu) { cpu_set_t affinity; CPU_ZERO(&affinity); CPU_SET(cpu, &affinity); if (sched_setaffinity(0, sizeof(affinity), &affinity)) err(1, "sched_setaffinity"); } static void dirty_on(int output_fd, int cpu) { int i, wrote; set_affinity(cpu); for (i = 0; i < 32; i++) { for (wrote = 0; wrote < bufSize; ) { int ret = write(output_fd, buf+wrote, bufSize-wrote); if (ret == -1) err(1, "write"); wrote += ret; } } } int main(int argc, char **argv) { int cpu, flush_cpu = 1, output_fd; const char *output; if (argc != 2) errx(1, "usage: output_file"); output = argv[1]; bufSize = getpagesize(); buf = malloc(getpagesize()); if (buf == NULL) errx(1, "malloc failed"); output_fd = open(output, O_CREAT|O_RDWR); if (output_fd == -1) err(1, "open(%s)", output); for (cpu = 0; cpu < get_nprocs(); cpu++) { if (cpu != flush_cpu) dirty_on(output_fd, cpu); } set_affinity(flush_cpu); if (fsync(output_fd)) err(1, "fsync(%s)", output); if (close(output_fd)) err(1, "close(%s)", output); free(buf); } Make balance_dirty_pages() and wb_over_bg_thresh() work harder to collect exact per memcg counters. This avoids the aforementioned oom kills. This does not affect the overhead of memory.stat, which still reads the single atomic counter. Why not use percpu_counter? memcg already handles cpus going offline, so no need for that overhead from percpu_counter. And the percpu_counter spinlocks are more heavyweight than is required. It probably also makes sense to use exact dirty and writeback counters in memcg oom reports. But that is saved for later. Link: http://lkml.kernel.org/r/20190329174609.164344-1-gthelen@google.com Signed-off-by: Greg Thelen <gthelen@google.com> Reviewed-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> [4.16+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Since commit a983b5ebee57 ("mm: memcontrol: fix excessive complexity in
memory.stat reporting") memcg dirty and writeback counters are managed
as:

 1) per-memcg per-cpu values in range of [-32..32]

 2) per-memcg atomic counter

When a per-cpu counter cannot fit in [-32..32] it's flushed to the
atomic.  Stat readers only check the atomic.  Thus readers such as
balance_dirty_pages() may see a nontrivial error margin: 32 pages per
cpu.

Assuming 100 cpus:
   4k x86 page_size:  13 MiB error per memcg
  64k ppc page_size: 200 MiB error per memcg

Considering that dirty+writeback are used together for some decisions the
errors double.

This inaccuracy can lead to undeserved oom kills.  One nasty case is
when all per-cpu counters hold positive values offsetting an atomic
negative value (i.e.  per_cpu[*]=32, atomic=n_cpu*-32).
balance_dirty_pages() only consults the atomic and does not consider
throttling the next n_cpu*32 dirty pages.  If the file_lru is in the
13..200 MiB range then there's absolutely no dirty throttling, which
burdens vmscan with only dirty+writeback pages thus resorting to oom
kill.

It could be argued that tiny containers are not supported, but it's more
subtle.  It's the amount the space available for file lru that matters.
If a container has memory.max-200MiB of non reclaimable memory, then it
will also suffer such oom kills on a 100 cpu machine.

The following test reliably ooms without this patch.  This patch avoids
oom kills.

  $ cat test
  mount -t cgroup2 none /dev/cgroup
  cd /dev/cgroup
  echo +io +memory > cgroup.subtree_control
  mkdir test
  cd test
  echo 10M > memory.max
  (echo $BASHPID > cgroup.procs && exec /memcg-writeback-stress /foo)
  (echo $BASHPID > cgroup.procs && exec dd if=/dev/zero of=/foo bs=2M count=100)

  $ cat memcg-writeback-stress.c
  /*
   * Dirty pages from all but one cpu.
   * Clean pages from the non dirtying cpu.
   * This is to stress per cpu counter imbalance.
   * On a 100 cpu machine:
   * - per memcg per cpu dirty count is 32 pages for each of 99 cpus
   * - per memcg atomic is -99*32 pages
   * - thus the complete dirty limit: sum of all counters 0
   * - balance_dirty_pages() only sees atomic count -99*32 pages, which
   *   it max()s to 0.
   * - So a workload can dirty -99*32 pages before balance_dirty_pages()
   *   cares.
   */
  #define _GNU_SOURCE
  #include <err.h>
  #include <fcntl.h>
  #include <sched.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <sys/stat.h>
  #include <sys/sysinfo.h>
  #include <sys/types.h>
  #include <unistd.h>

  static char *buf;
  static int bufSize;

  static void set_affinity(int cpu)
  {
  	cpu_set_t affinity;

  	CPU_ZERO(&affinity);
  	CPU_SET(cpu, &affinity);
  	if (sched_setaffinity(0, sizeof(affinity), &affinity))
  		err(1, "sched_setaffinity");
  }

  static void dirty_on(int output_fd, int cpu)
  {
  	int i, wrote;

  	set_affinity(cpu);
  	for (i = 0; i < 32; i++) {
  		for (wrote = 0; wrote < bufSize; ) {
  			int ret = write(output_fd, buf+wrote, bufSize-wrote);
  			if (ret == -1)
  				err(1, "write");
  			wrote += ret;
  		}
  	}
  }

  int main(int argc, char **argv)
  {
  	int cpu, flush_cpu = 1, output_fd;
  	const char *output;

  	if (argc != 2)
  		errx(1, "usage: output_file");

  	output = argv[1];
  	bufSize = getpagesize();
  	buf = malloc(getpagesize());
  	if (buf == NULL)
  		errx(1, "malloc failed");

  	output_fd = open(output, O_CREAT|O_RDWR);
  	if (output_fd == -1)
  		err(1, "open(%s)", output);

  	for (cpu = 0; cpu < get_nprocs(); cpu++) {
  		if (cpu != flush_cpu)
  			dirty_on(output_fd, cpu);
  	}

  	set_affinity(flush_cpu);
  	if (fsync(output_fd))
  		err(1, "fsync(%s)", output);
  	if (close(output_fd))
  		err(1, "close(%s)", output);
  	free(buf);
  }

Make balance_dirty_pages() and wb_over_bg_thresh() work harder to
collect exact per memcg counters.  This avoids the aforementioned oom
kills.

This does not affect the overhead of memory.stat, which still reads the
single atomic counter.

Why not use percpu_counter? memcg already handles cpus going offline, so
no need for that overhead from percpu_counter.  And the percpu_counter
spinlocks are more heavyweight than is required.

It probably also makes sense to use exact dirty and writeback counters
in memcg oom reports.  But that is saved for later.

Link: http://lkml.kernel.org/r/20190329174609.164344-1-gthelen@google.com
Signed-off-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>	[4.16+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/huge_memory.c: fix modifying of page protection by insert_pfn_pmd() 2019-04-06T02:02:31+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2019-04-06T01:39:10+00:00 c6f3c5ee40c10bb65725047a220570f718507001 With some architectures like ppc64, set_pmd_at() cannot cope with a situation where there is already some (different) valid entry present. Use pmdp_set_access_flags() instead to modify the pfn which is built to deal with modifying existing PMD entries. This is similar to commit cae85cb8add3 ("mm/memory.c: fix modifying of page protection by insert_pfn()") We also do similar update w.r.t insert_pfn_pud eventhough ppc64 don't support pud pfn entries now. Without this patch we also see the below message in kernel log "BUG: non-zero pgtables_bytes on freeing mm:" Link: http://lkml.kernel.org/r/20190402115125.18803-1-aneesh.kumar@linux.ibm.com Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reported-by: Chandan Rajendra <chandan@linux.ibm.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Dan Williams <dan.j.williams@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
With some architectures like ppc64, set_pmd_at() cannot cope with a
situation where there is already some (different) valid entry present.

Use pmdp_set_access_flags() instead to modify the pfn which is built to
deal with modifying existing PMD entries.

This is similar to commit cae85cb8add3 ("mm/memory.c: fix modifying of
page protection by insert_pfn()")

We also do similar update w.r.t insert_pfn_pud eventhough ppc64 don't
support pud pfn entries now.

Without this patch we also see the below message in kernel log "BUG:
non-zero pgtables_bytes on freeing mm:"

Link: http://lkml.kernel.org/r/20190402115125.18803-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Chandan Rajendra <chandan@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kmemleak: powerpc: skip scanning holes in the .bss section 2019-04-06T02:02:30+00:00 Catalin Marinas catalin.marinas@arm.com 2019-04-06T01:38:49+00:00 298a32b132087550d3fa80641ca58323c5dfd4d9 Commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds kvm_tmp[] into the .bss section and then free the rest of unused spaces back to the page allocator. kernel_init kvm_guest_init kvm_free_tmp free_reserved_area free_unref_page free_unref_page_prepare With DEBUG_PAGEALLOC=y, it will unmap those pages from kernel. As the result, kmemleak scan will trigger a panic when it scans the .bss section with unmapped pages. This patch creates dedicated kmemleak objects for the .data, .bss and potentially .data..ro_after_init sections to allow partial freeing via the kmemleak_free_part() in the powerpc kvm_free_tmp() function. Link: http://lkml.kernel.org/r/20190321171917.62049-1-catalin.marinas@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Qian Cai <cai@lca.pw> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Tested-by: Qian Cai <cai@lca.pw> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Avi Kivity <avi@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krcmar <rkrcmar@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds
kvm_tmp[] into the .bss section and then free the rest of unused spaces
back to the page allocator.

kernel_init
  kvm_guest_init
    kvm_free_tmp
      free_reserved_area
        free_unref_page
          free_unref_page_prepare

With DEBUG_PAGEALLOC=y, it will unmap those pages from kernel.  As the
result, kmemleak scan will trigger a panic when it scans the .bss
section with unmapped pages.

This patch creates dedicated kmemleak objects for the .data, .bss and
potentially .data..ro_after_init sections to allow partial freeing via
the kmemleak_free_part() in the powerpc kvm_free_tmp() function.

Link: http://lkml.kernel.org/r/20190321171917.62049-1-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Qian Cai <cai@lca.pw>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Qian Cai <cai@lca.pw>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/compaction.c: abort search if isolation fails 2019-04-04T10:56:15+00:00 Qian Cai cai@lca.pw 2019-04-04T10:54:41+00:00 5b56d996dd50a9d2ca87c25ebb50c07b255b7e04 Running LTP oom01 in a tight loop or memory stress testing put the system in a low-memory situation could triggers random memory corruption like page flag corruption below due to in fast_isolate_freepages(), if isolation fails, next_search_order() does not abort the search immediately could lead to improper accesses. UBSAN: Undefined behaviour in ./include/linux/mm.h:1195:50 index 7 is out of range for type 'zone [5]' Call Trace: dump_stack+0x62/0x9a ubsan_epilogue+0xd/0x7f __ubsan_handle_out_of_bounds+0x14d/0x192 __isolate_free_page+0x52c/0x600 compaction_alloc+0x886/0x25f0 unmap_and_move+0x37/0x1e70 migrate_pages+0x2ca/0xb20 compact_zone+0x19cb/0x3620 kcompactd_do_work+0x2df/0x680 kcompactd+0x1d8/0x6c0 kthread+0x32c/0x3f0 ret_from_fork+0x35/0x40 ------------[ cut here ]------------ kernel BUG at mm/page_alloc.c:3124! invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI RIP: 0010:__isolate_free_page+0x464/0x600 RSP: 0000:ffff888b9e1af848 EFLAGS: 00010007 RAX: 0000000030000000 RBX: ffff888c39fcf0f8 RCX: 0000000000000000 RDX: 1ffff111873f9e25 RSI: 0000000000000004 RDI: ffffed1173c35ef6 RBP: ffff888b9e1af898 R08: fffffbfff4fc2461 R09: fffffbfff4fc2460 R10: fffffbfff4fc2460 R11: ffffffffa7e12303 R12: 0000000000000008 R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000007 FS: 0000000000000000(0000) GS:ffff888ba8e80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc7abc00000 CR3: 0000000752416004 CR4: 00000000001606a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: compaction_alloc+0x886/0x25f0 unmap_and_move+0x37/0x1e70 migrate_pages+0x2ca/0xb20 compact_zone+0x19cb/0x3620 kcompactd_do_work+0x2df/0x680 kcompactd+0x1d8/0x6c0 kthread+0x32c/0x3f0 ret_from_fork+0x35/0x40 Link: http://lkml.kernel.org/r/20190320192648.52499-1-cai@lca.pw Fixes: dbe2d4e4f12e ("mm, compaction: round-robin the order while searching the free lists for a target") Signed-off-by: Qian Cai <cai@lca.pw> Acked-by: Mel Gorman <mgorman@techsingularity.net> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by: Mel Gorman <mgorman@techsingularity.net> 
Running LTP oom01 in a tight loop or memory stress testing put the system
in a low-memory situation could triggers random memory corruption like
page flag corruption below due to in fast_isolate_freepages(), if
isolation fails, next_search_order() does not abort the search immediately
could lead to improper accesses.

UBSAN: Undefined behaviour in ./include/linux/mm.h:1195:50
index 7 is out of range for type 'zone [5]'
Call Trace:
 dump_stack+0x62/0x9a
 ubsan_epilogue+0xd/0x7f
 __ubsan_handle_out_of_bounds+0x14d/0x192
 __isolate_free_page+0x52c/0x600
 compaction_alloc+0x886/0x25f0
 unmap_and_move+0x37/0x1e70
 migrate_pages+0x2ca/0xb20
 compact_zone+0x19cb/0x3620
 kcompactd_do_work+0x2df/0x680
 kcompactd+0x1d8/0x6c0
 kthread+0x32c/0x3f0
 ret_from_fork+0x35/0x40
------------[ cut here ]------------
kernel BUG at mm/page_alloc.c:3124!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
RIP: 0010:__isolate_free_page+0x464/0x600
RSP: 0000:ffff888b9e1af848 EFLAGS: 00010007
RAX: 0000000030000000 RBX: ffff888c39fcf0f8 RCX: 0000000000000000
RDX: 1ffff111873f9e25 RSI: 0000000000000004 RDI: ffffed1173c35ef6
RBP: ffff888b9e1af898 R08: fffffbfff4fc2461 R09: fffffbfff4fc2460
R10: fffffbfff4fc2460 R11: ffffffffa7e12303 R12: 0000000000000008
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000007
FS:  0000000000000000(0000) GS:ffff888ba8e80000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc7abc00000 CR3: 0000000752416004 CR4: 00000000001606a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 compaction_alloc+0x886/0x25f0
 unmap_and_move+0x37/0x1e70
 migrate_pages+0x2ca/0xb20
 compact_zone+0x19cb/0x3620
 kcompactd_do_work+0x2df/0x680
 kcompactd+0x1d8/0x6c0
 kthread+0x32c/0x3f0
 ret_from_fork+0x35/0x40

Link: http://lkml.kernel.org/r/20190320192648.52499-1-cai@lca.pw
Fixes: dbe2d4e4f12e ("mm, compaction: round-robin the order while searching the free lists for a target")
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
mm/compaction.c: correct zone boundary handling when resetting pageblock skip hints 2019-04-04T10:56:01+00:00 Mel Gorman mgorman@techsingularity.net 2019-04-04T10:54:09+00:00 6b0868c820ff7370d15d6ddfe71b1ce6bbe8a25d Mikhail Gavrilo reported the following bug being triggered in a Fedora kernel based on 5.1-rc1 but it is relevant to a vanilla kernel. kernel: page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) kernel: ------------[ cut here ]------------ kernel: kernel BUG at include/linux/mm.h:1021! kernel: invalid opcode: 0000 [#1] SMP NOPTI kernel: CPU: 6 PID: 116 Comm: kswapd0 Tainted: G C 5.1.0-0.rc1.git1.3.fc31.x86_64 #1 kernel: Hardware name: System manufacturer System Product Name/ROG STRIX X470-I GAMING, BIOS 1201 12/07/2018 kernel: RIP: 0010:__reset_isolation_pfn+0x244/0x2b0 kernel: Code: fe 06 e8 0f 8e fc ff 44 0f b6 4c 24 04 48 85 c0 0f 85 dc fe ff ff e9 68 fe ff ff 48 c7 c6 58 b7 2e 8c 4c 89 ff e8 0c 75 00 00 <0f> 0b 48 c7 c6 58 b7 2e 8c e8 fe 74 00 00 0f 0b 48 89 fa 41 b8 01 kernel: RSP: 0018:ffff9e2d03f0fde8 EFLAGS: 00010246 kernel: RAX: 0000000000000034 RBX: 000000000081f380 RCX: ffff8cffbddd6c20 kernel: RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8cffbddd6c20 kernel: RBP: 0000000000000001 R08: 0000009898b94613 R09: 0000000000000000 kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000100000 kernel: R13: 0000000000100000 R14: 0000000000000001 R15: ffffca7de07ce000 kernel: FS: 0000000000000000(0000) GS:ffff8cffbdc00000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: CR2: 00007fc1670e9000 CR3: 00000007f5276000 CR4: 00000000003406e0 kernel: Call Trace: kernel: __reset_isolation_suitable+0x62/0x120 kernel: reset_isolation_suitable+0x3b/0x40 kernel: kswapd+0x147/0x540 kernel: ? finish_wait+0x90/0x90 kernel: kthread+0x108/0x140 kernel: ? balance_pgdat+0x560/0x560 kernel: ? kthread_park+0x90/0x90 kernel: ret_from_fork+0x27/0x50 He bisected it down to e332f741a8dd ("mm, compaction: be selective about what pageblocks to clear skip hints"). The problem is that the patch in question was sloppy with respect to the handling of zone boundaries. In some instances, it was possible for PFNs outside of a zone to be examined and if those were not properly initialised or poisoned then it would trigger the VM_BUG_ON. This patch corrects the zone boundary issues when resetting pageblock skip hints and Mikhail reported that the bug did not trigger after 30 hours of testing. Link: http://lkml.kernel.org/r/20190327085424.GL3189@techsingularity.net Fixes: e332f741a8dd ("mm, compaction: be selective about what pageblocks to clear skip hints") Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Qian Cai <cai@lca.pw> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Mel Gorman <mgorman@techsingularity.net> 
Mikhail Gavrilo reported the following bug being triggered in a Fedora
kernel based on 5.1-rc1 but it is relevant to a vanilla kernel.

 kernel: page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 kernel: ------------[ cut here ]------------
 kernel: kernel BUG at include/linux/mm.h:1021!
 kernel: invalid opcode: 0000 [#1] SMP NOPTI
 kernel: CPU: 6 PID: 116 Comm: kswapd0 Tainted: G         C        5.1.0-0.rc1.git1.3.fc31.x86_64 #1
 kernel: Hardware name: System manufacturer System Product Name/ROG STRIX X470-I GAMING, BIOS 1201 12/07/2018
 kernel: RIP: 0010:__reset_isolation_pfn+0x244/0x2b0
 kernel: Code: fe 06 e8 0f 8e fc ff 44 0f b6 4c 24 04 48 85 c0 0f 85 dc fe ff ff e9 68 fe ff ff 48 c7 c6 58 b7 2e 8c 4c 89 ff e8 0c 75 00 00 <0f> 0b 48 c7 c6 58 b7 2e 8c e8 fe 74 00 00 0f 0b 48 89 fa 41 b8 01
 kernel: RSP: 0018:ffff9e2d03f0fde8 EFLAGS: 00010246
 kernel: RAX: 0000000000000034 RBX: 000000000081f380 RCX: ffff8cffbddd6c20
 kernel: RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8cffbddd6c20
 kernel: RBP: 0000000000000001 R08: 0000009898b94613 R09: 0000000000000000
 kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000100000
 kernel: R13: 0000000000100000 R14: 0000000000000001 R15: ffffca7de07ce000
 kernel: FS:  0000000000000000(0000) GS:ffff8cffbdc00000(0000) knlGS:0000000000000000
 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 kernel: CR2: 00007fc1670e9000 CR3: 00000007f5276000 CR4: 00000000003406e0
 kernel: Call Trace:
 kernel:  __reset_isolation_suitable+0x62/0x120
 kernel:  reset_isolation_suitable+0x3b/0x40
 kernel:  kswapd+0x147/0x540
 kernel:  ? finish_wait+0x90/0x90
 kernel:  kthread+0x108/0x140
 kernel:  ? balance_pgdat+0x560/0x560
 kernel:  ? kthread_park+0x90/0x90
 kernel:  ret_from_fork+0x27/0x50

He bisected it down to e332f741a8dd ("mm, compaction: be selective about
what pageblocks to clear skip hints").  The problem is that the patch in
question was sloppy with respect to the handling of zone boundaries.  In
some instances, it was possible for PFNs outside of a zone to be examined
and if those were not properly initialised or poisoned then it would
trigger the VM_BUG_ON.  This patch corrects the zone boundary issues when
resetting pageblock skip hints and Mikhail reported that the bug did not
trigger after 30 hours of testing.

Link: http://lkml.kernel.org/r/20190327085424.GL3189@techsingularity.net
Fixes: e332f741a8dd ("mm, compaction: be selective about what pageblocks to clear skip hints")
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
mm/migrate.c: add missing flush_dcache_page for non-mapped page migrate 2019-03-29T17:01:37+00:00 Lars Persson lars.persson@axis.com 2019-03-29T03:44:28+00:00 d2b2c6dd227ba5b8a802858748ec9a780cb75b47 Our MIPS 1004Kc SoCs were seeing random userspace crashes with SIGILL and SIGSEGV that could not be traced back to a userspace code bug. They had all the magic signs of an I/D cache coherency issue. Now recently we noticed that the /proc/sys/vm/compact_memory interface was quite efficient at provoking this class of userspace crashes. Studying the code in mm/migrate.c there is a distinction made between migrating a page that is mapped at the instant of migration and one that is not mapped. Our problem turned out to be the non-mapped pages. For the non-mapped page the code performs a copy of the page content and all relevant meta-data of the page without doing the required D-cache maintenance. This leaves dirty data in the D-cache of the CPU and on the 1004K cores this data is not visible to the I-cache. A subsequent page-fault that triggers a mapping of the page will happily serve the process with potentially stale code. What about ARM then, this bug should have seen greater exposure? Well ARM became immune to this flaw back in 2010, see commit c01778001a4f ("ARM: 6379/1: Assume new page cache pages have dirty D-cache"). My proposed fix moves the D-cache maintenance inside move_to_new_page to make it common for both cases. Link: http://lkml.kernel.org/r/20190315083502.11849-1-larper@axis.com Fixes: 97ee0524614 ("flush cache before installing new page at migraton") Signed-off-by: Lars Persson <larper@axis.com> Reviewed-by: Paul Burton <paul.burton@mips.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Our MIPS 1004Kc SoCs were seeing random userspace crashes with SIGILL
and SIGSEGV that could not be traced back to a userspace code bug.  They
had all the magic signs of an I/D cache coherency issue.

Now recently we noticed that the /proc/sys/vm/compact_memory interface
was quite efficient at provoking this class of userspace crashes.

Studying the code in mm/migrate.c there is a distinction made between
migrating a page that is mapped at the instant of migration and one that
is not mapped.  Our problem turned out to be the non-mapped pages.

For the non-mapped page the code performs a copy of the page content and
all relevant meta-data of the page without doing the required D-cache
maintenance.  This leaves dirty data in the D-cache of the CPU and on
the 1004K cores this data is not visible to the I-cache.  A subsequent
page-fault that triggers a mapping of the page will happily serve the
process with potentially stale code.

What about ARM then, this bug should have seen greater exposure? Well
ARM became immune to this flaw back in 2010, see commit c01778001a4f
("ARM: 6379/1: Assume new page cache pages have dirty D-cache").

My proposed fix moves the D-cache maintenance inside move_to_new_page to
make it common for both cases.

Link: http://lkml.kernel.org/r/20190315083502.11849-1-larper@axis.com
Fixes: 97ee0524614 ("flush cache before installing new page at migraton")
Signed-off-by: Lars Persson <larper@axis.com>
Reviewed-by: Paul Burton <paul.burton@mips.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/page_isolation.c: fix a wrong flag in set_migratetype_isolate() 2019-03-29T17:01:37+00:00 Qian Cai cai@lca.pw 2019-03-29T03:44:21+00:00 f5777bc2d9cf0712554228b1a7927b6f13f5c1f0 Due to has_unmovable_pages() taking an incorrect irqsave flag instead of the isolation flag in set_migratetype_isolate(), there are issues with HWPOSION and error reporting where dump_page() is not called when there is an unmovable page. Link: http://lkml.kernel.org/r/20190320204941.53731-1-cai@lca.pw Fixes: d381c54760dc ("mm: only report isolation failures when offlining memory") Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Signed-off-by: Qian Cai <cai@lca.pw> Cc: <stable@vger.kernel.org> [5.0.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Due to has_unmovable_pages() taking an incorrect irqsave flag instead of
the isolation flag in set_migratetype_isolate(), there are issues with
HWPOSION and error reporting where dump_page() is not called when there
is an unmovable page.

Link: http://lkml.kernel.org/r/20190320204941.53731-1-cai@lca.pw
Fixes: d381c54760dc ("mm: only report isolation failures when offlining memory")
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Qian Cai <cai@lca.pw>
Cc: <stable@vger.kernel.org>	[5.0.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memory_hotplug.c: fix notification in offline error path 2019-03-29T17:01:37+00:00 Qian Cai cai@lca.pw 2019-03-29T03:44:16+00:00 c4efe484b5f0d768e23c9731082fec827723e738 When start_isolate_page_range() returned -EBUSY in __offline_pages(), it calls memory_notify(MEM_CANCEL_OFFLINE, &arg) with an uninitialized "arg". As the result, it triggers warnings below. Also, it is only necessary to notify MEM_CANCEL_OFFLINE after MEM_GOING_OFFLINE. page:ffffea0001200000 count:1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x3fffe000001000(reserved) raw: 003fffe000001000 ffffea0001200008 ffffea0001200008 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: unmovable page WARNING: CPU: 25 PID: 1665 at mm/kasan/common.c:665 kasan_mem_notifier+0x34/0x23b CPU: 25 PID: 1665 Comm: bash Tainted: G W 5.0.0+ #94 Hardware name: HP ProLiant DL180 Gen9/ProLiant DL180 Gen9, BIOS U20 10/25/2017 RIP: 0010:kasan_mem_notifier+0x34/0x23b RSP: 0018:ffff8883ec737890 EFLAGS: 00010206 RAX: 0000000000000246 RBX: ff10f0f4435f1000 RCX: f887a7a21af88000 RDX: dffffc0000000000 RSI: 0000000000000020 RDI: ffff8881f221af88 RBP: ffff8883ec737898 R08: ffff888000000000 R09: ffffffffb0bddcd0 R10: ffffed103e857088 R11: ffff8881f42b8443 R12: dffffc0000000000 R13: 00000000fffffff9 R14: dffffc0000000000 R15: 0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000560fbd31d730 CR3: 00000004049c6003 CR4: 00000000001606a0 Call Trace: notifier_call_chain+0xbf/0x130 __blocking_notifier_call_chain+0x76/0xc0 blocking_notifier_call_chain+0x16/0x20 memory_notify+0x1b/0x20 __offline_pages+0x3e2/0x1210 offline_pages+0x11/0x20 memory_block_action+0x144/0x300 memory_subsys_offline+0xe5/0x170 device_offline+0x13f/0x1e0 state_store+0xeb/0x110 dev_attr_store+0x3f/0x70 sysfs_kf_write+0x104/0x150 kernfs_fop_write+0x25c/0x410 __vfs_write+0x66/0x120 vfs_write+0x15a/0x4f0 ksys_write+0xd2/0x1b0 __x64_sys_write+0x73/0xb0 do_syscall_64+0xeb/0xb78 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f14f75cc3b8 RSP: 002b:00007ffe84d01d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007f14f75cc3b8 RDX: 0000000000000008 RSI: 0000563f8e433d70 RDI: 0000000000000001 RBP: 0000563f8e433d70 R08: 000000000000000a R09: 00007ffe84d018f0 R10: 000000000000000a R11: 0000000000000246 R12: 00007f14f789e780 R13: 0000000000000008 R14: 00007f14f7899740 R15: 0000000000000008 Link: http://lkml.kernel.org/r/20190320204255.53571-1-cai@lca.pw Fixes: 7960509329c2 ("mm, memory_hotplug: print reason for the offlining failure") Reviewed-by: Oscar Salvador <osalvador@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Qian Cai <cai@lca.pw> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@vger.kernel.org> [5.0.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
When start_isolate_page_range() returned -EBUSY in __offline_pages(), it
calls memory_notify(MEM_CANCEL_OFFLINE, &arg) with an uninitialized
"arg".  As the result, it triggers warnings below.  Also, it is only
necessary to notify MEM_CANCEL_OFFLINE after MEM_GOING_OFFLINE.

  page:ffffea0001200000 count:1 mapcount:0 mapping:0000000000000000
  index:0x0
  flags: 0x3fffe000001000(reserved)
  raw: 003fffe000001000 ffffea0001200008 ffffea0001200008 0000000000000000
  raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
  page dumped because: unmovable page
  WARNING: CPU: 25 PID: 1665 at mm/kasan/common.c:665
  kasan_mem_notifier+0x34/0x23b
  CPU: 25 PID: 1665 Comm: bash Tainted: G        W         5.0.0+ #94
  Hardware name: HP ProLiant DL180 Gen9/ProLiant DL180 Gen9, BIOS U20
  10/25/2017
  RIP: 0010:kasan_mem_notifier+0x34/0x23b
  RSP: 0018:ffff8883ec737890 EFLAGS: 00010206
  RAX: 0000000000000246 RBX: ff10f0f4435f1000 RCX: f887a7a21af88000
  RDX: dffffc0000000000 RSI: 0000000000000020 RDI: ffff8881f221af88
  RBP: ffff8883ec737898 R08: ffff888000000000 R09: ffffffffb0bddcd0
  R10: ffffed103e857088 R11: ffff8881f42b8443 R12: dffffc0000000000
  R13: 00000000fffffff9 R14: dffffc0000000000 R15: 0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000560fbd31d730 CR3: 00000004049c6003 CR4: 00000000001606a0
  Call Trace:
   notifier_call_chain+0xbf/0x130
   __blocking_notifier_call_chain+0x76/0xc0
   blocking_notifier_call_chain+0x16/0x20
   memory_notify+0x1b/0x20
   __offline_pages+0x3e2/0x1210
   offline_pages+0x11/0x20
   memory_block_action+0x144/0x300
   memory_subsys_offline+0xe5/0x170
   device_offline+0x13f/0x1e0
   state_store+0xeb/0x110
   dev_attr_store+0x3f/0x70
   sysfs_kf_write+0x104/0x150
   kernfs_fop_write+0x25c/0x410
   __vfs_write+0x66/0x120
   vfs_write+0x15a/0x4f0
   ksys_write+0xd2/0x1b0
   __x64_sys_write+0x73/0xb0
   do_syscall_64+0xeb/0xb78
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f14f75cc3b8
  RSP: 002b:00007ffe84d01d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007f14f75cc3b8
  RDX: 0000000000000008 RSI: 0000563f8e433d70 RDI: 0000000000000001
  RBP: 0000563f8e433d70 R08: 000000000000000a R09: 00007ffe84d018f0
  R10: 000000000000000a R11: 0000000000000246 R12: 00007f14f789e780
  R13: 0000000000000008 R14: 00007f14f7899740 R15: 0000000000000008

Link: http://lkml.kernel.org/r/20190320204255.53571-1-cai@lca.pw
Fixes: 7960509329c2 ("mm, memory_hotplug: print reason for the offlining failure")
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>	[5.0.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/debug.c: fix __dump_page when mapping->host is not set 2019-03-29T17:01:37+00:00 Oscar Salvador osalvador@suse.de 2019-03-29T03:44:01+00:00 5ae2efb1dea9f537453e841714e3ee2757595aec While debugging something, I added a dump_page() into do_swap_page(), and I got the splat from below. The issue happens when dereferencing mapping->host in __dump_page(): ... else if (mapping) { pr_warn("%ps ", mapping->a_ops); if (mapping->host->i_dentry.first) { struct dentry *dentry; dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias); pr_warn("name:\"%pd\" ", dentry); } } ... Swap address space does not contain an inode information, and so mapping->host equals NULL. Although the dump_page() call was added artificially into do_swap_page(), I am not sure if we can hit this from any other path, so it looks worth fixing it. We can easily do that by checking mapping->host first. Link: http://lkml.kernel.org/r/20190318072931.29094-1-osalvador@suse.de Fixes: 1c6fb1d89e73c ("mm: print more information about mapping in __dump_page") Signed-off-by: Oscar Salvador <osalvador@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
While debugging something, I added a dump_page() into do_swap_page(),
and I got the splat from below.  The issue happens when dereferencing
mapping->host in __dump_page():

  ...
  else if (mapping) {
	pr_warn("%ps ", mapping->a_ops);
	if (mapping->host->i_dentry.first) {
		struct dentry *dentry;
		dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias);
		pr_warn("name:\"%pd\" ", dentry);
	}
  }
  ...

Swap address space does not contain an inode information, and so
mapping->host equals NULL.

Although the dump_page() call was added artificially into
do_swap_page(), I am not sure if we can hit this from any other path, so
it looks worth fixing it.  We can easily do that by checking
mapping->host first.

Link: http://lkml.kernel.org/r/20190318072931.29094-1-osalvador@suse.de
Fixes: 1c6fb1d89e73c ("mm: print more information about mapping in __dump_page")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>