linux-stable.git/mm, branch v4.16.4

writeback: safer lock nesting

2018-04-24T07:43:11+00:00

commit 2e898e4c0a3897ccd434adac5abb8330194f527b upstream.

lock_page_memcg()/unlock_page_memcg() use spin_lock_irqsave/restore() if
the page's memcg is undergoing move accounting, which occurs when a
process leaves its memcg for a new one that has
memory.move_charge_at_immigrate set.

unlocked_inode_to_wb_begin,end() use spin_lock_irq/spin_unlock_irq() if
the given inode is switching writeback domains.  Switches occur when
enough writes are issued from a new domain.

This existing pattern is thus suspicious:
    lock_page_memcg(page);
    unlocked_inode_to_wb_begin(inode, &locked);
    ...
    unlocked_inode_to_wb_end(inode, locked);
    unlock_page_memcg(page);

If both inode switch and process memcg migration are both in-flight then
unlocked_inode_to_wb_end() will unconditionally enable interrupts while
still holding the lock_page_memcg() irq spinlock.  This suggests the
possibility of deadlock if an interrupt occurs before unlock_page_memcg().

    truncate
    __cancel_dirty_page
    lock_page_memcg
    unlocked_inode_to_wb_begin
    unlocked_inode_to_wb_end
    
                                    
                                    end_page_writeback
                                    test_clear_page_writeback
                                    lock_page_memcg
                                    
    unlock_page_memcg

Due to configuration limitations this deadlock is not currently possible
because we don't mix cgroup writeback (a cgroupv2 feature) and
memory.move_charge_at_immigrate (a cgroupv1 feature).

If the kernel is hacked to always claim inode switching and memcg
moving_account, then this script triggers lockup in less than a minute:

  cd /mnt/cgroup/memory
  mkdir a b
  echo 1 > a/memory.move_charge_at_immigrate
  echo 1 > b/memory.move_charge_at_immigrate
  (
    echo $BASHPID > a/cgroup.procs
    while true; do
      dd if=/dev/zero of=/mnt/big bs=1M count=256
    done
  ) &
  while true; do
    sync
  done &
  sleep 1h &
  SLEEP=$!
  while true; do
    echo $SLEEP > a/cgroup.procs
    echo $SLEEP > b/cgroup.procs
  done

The deadlock does not seem possible, so it's debatable if there's any
reason to modify the kernel.  I suggest we should to prevent future
surprises.  And Wang Long said "this deadlock occurs three times in our
environment", so there's more reason to apply this, even to stable.
Stable 4.4 has minor conflicts applying this patch.  For a clean 4.4 patch
see "[PATCH for-4.4] writeback: safer lock nesting"
https://lkml.org/lkml/2018/4/11/146

Wang Long said "this deadlock occurs three times in our environment"

[gthelen@google.com: v4]
  Link: http://lkml.kernel.org/r/20180411084653.254724-1-gthelen@google.com
[akpm@linux-foundation.org: comment tweaks, struct initialization simplification]
Change-Id: Ibb773e8045852978f6207074491d262f1b3fb613
Link: http://lkml.kernel.org/r/20180410005908.167976-1-gthelen@google.com
Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates")
Signed-off-by: Greg Thelen 
Reported-by: Wang Long 
Acked-by: Wang Long 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Cc: Johannes Weiner 
Cc: Tejun Heo 
Cc: Nicholas Piggin 
Cc: 	[v4.2+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[natechancellor: Adjust context due to lack of b93b016313b3b]
Signed-off-by: Nathan Chancellor 
Signed-off-by: Greg Kroah-Hartman

mm/filemap.c: fix NULL pointer in page_cache_tree_insert()

2018-04-24T07:43:10+00:00

commit abc1be13fd113ddef5e2d807a466286b864caed3 upstream.

f2fs specifies the __GFP_ZERO flag for allocating some of its pages.
Unfortunately, the page cache also uses the mapping's GFP flags for
allocating radix tree nodes.  It always masked off the __GFP_HIGHMEM
flag, and masks off __GFP_ZERO in some paths, but not all.  That causes
radix tree nodes to be allocated with a NULL list_head, which causes
backtraces like:

  __list_del_entry+0x30/0xd0
  list_lru_del+0xac/0x1ac
  page_cache_tree_insert+0xd8/0x110

The __GFP_DMA and __GFP_DMA32 flags would also be able to sneak through
if they are ever used.  Fix them all by using GFP_RECLAIM_MASK at the
innermost location, and remove it from earlier in the callchain.

Link: http://lkml.kernel.org/r/20180411060320.14458-2-willy@infradead.org
Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check")
Signed-off-by: Matthew Wilcox 
Reported-by: Chris Fries 
Debugged-by: Minchan Kim 
Acked-by: Johannes Weiner 
Acked-by: Michal Hocko 
Reviewed-by: Jan Kara 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm, slab: reschedule cache_reap() on the same CPU

2018-04-24T07:42:50+00:00

commit a9f2a846f0503e7d729f552e3ccfe2279010fe94 upstream.

cache_reap() is initially scheduled in start_cpu_timer() via
schedule_delayed_work_on(). But then the next iterations are scheduled
via schedule_delayed_work(), i.e. using WORK_CPU_UNBOUND.

Thus since commit ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND
work on wq_unbound_cpumask CPUs") there is no guarantee the future
iterations will run on the originally intended cpu, although it's still
preferred.  I was able to demonstrate this with
/sys/module/workqueue/parameters/debug_force_rr_cpu.  IIUC, it may also
happen due to migrating timers in nohz context.  As a result, some cpu's
would be calling cache_reap() more frequently and others never.

This patch uses schedule_delayed_work_on() with the current cpu when
scheduling the next iteration.

Link: http://lkml.kernel.org/r/20180411070007.32225-1-vbabka@suse.cz
Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs")
Signed-off-by: Vlastimil Babka 
Acked-by: Pekka Enberg 
Acked-by: Christoph Lameter 
Cc: Joonsoo Kim 
Cc: David Rientjes 
Cc: Tejun Heo 
Cc: Lai Jiangshan 
Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Stephen Boyd 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: hwpoison: disable memory error handling on 1GB hugepage

2018-04-24T07:42:49+00:00

commit 31286a8484a85e8b4e91ddb0f5415aee8a416827 upstream.

Recently the following BUG was reported:

    Injecting memory failure for pfn 0x3c0000 at process virtual address 0x7fe300000000
    Memory failure: 0x3c0000: recovery action for huge page: Recovered
    BUG: unable to handle kernel paging request at ffff8dfcc0003000
    IP: gup_pgd_range+0x1f0/0xc20
    PGD 17ae72067 P4D 17ae72067 PUD 0
    Oops: 0000 [#1] SMP PTI
    ...
    CPU: 3 PID: 5467 Comm: hugetlb_1gb Not tainted 4.15.0-rc8-mm1-abc+ #3
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014

You can easily reproduce this by calling madvise(MADV_HWPOISON) twice on
a 1GB hugepage.  This happens because get_user_pages_fast() is not aware
of a migration entry on pud that was created in the 1st madvise() event.

I think that conversion to pud-aligned migration entry is working, but
other MM code walking over page table isn't prepared for it.  We need
some time and effort to make all this work properly, so this patch
avoids the reported bug by just disabling error handling for 1GB
hugepage.

[n-horiguchi@ah.jp.nec.com: v2]
  Link: http://lkml.kernel.org/r/1517284444-18149-1-git-send-email-n-horiguchi@ah.jp.nec.com
Link: http://lkml.kernel.org/r/1517207283-15769-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Reviewed-by: Mike Kravetz 
Acked-by: Punit Agrawal 
Tested-by: Michael Ellerman 
Cc: Anshuman Khandual 
Cc: "Aneesh Kumar K.V" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/hmm: hmm_pfns_bad() was accessing wrong struct

2018-04-24T07:42:49+00:00

commit c719547f032d4610c7a20900baacae26d0b1ff3e upstream.

The private field of mm_walk struct point to an hmm_vma_walk struct and
not to the hmm_range struct desired.  Fix to get proper struct pointer.

Link: http://lkml.kernel.org/r/20180323005527.758-6-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Cc: Evgeny Baskakov 
Cc: Ralph Campbell 
Cc: Mark Hairgrove 
Cc: John Hubbard 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/ksm.c: fix inconsistent accounting of zero pages

2018-04-24T07:42:48+00:00

commit a38c015f3156895b07e71d4e4414289f8a3b2745 upstream.

When using KSM with use_zero_pages, we replace anonymous pages
containing only zeroes with actual zero pages, which are not anonymous.
We need to do proper accounting of the mm counters, otherwise we will
get wrong values in /proc and a BUG message in dmesg when tearing down
the mm.

Link: http://lkml.kernel.org/r/1522931274-15552-1-git-send-email-imbrenda@linux.vnet.ibm.com
Fixes: e86c59b1b1 ("mm/ksm: improve deduplication of zero pages with colouring")
Signed-off-by: Claudio Imbrenda 
Reviewed-by: Andrew Morton 
Cc: Andrea Arcangeli 
Cc: Minchan Kim 
Cc: Kirill A. Shutemov 
Cc: Hugh Dickins 
Cc: Christian Borntraeger 
Cc: Gerald Schaefer 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/gup_benchmark: handle gup failures

2018-04-19T06:54:12+00:00

commit 09e35a4a1ca8b9988ca9b8557d17948cd6c0808b upstream.

Patch series "mm/get_user_pages_fast fixes, cleanups", v2.

Turns out get_user_pages_fast and __get_user_pages_fast return different
values on error when given a single page: __get_user_pages_fast returns
0.  get_user_pages_fast returns either 0 or an error.

Callers of get_user_pages_fast expect an error so fix it up to return an
error consistently.

Stress the difference between get_user_pages_fast and
__get_user_pages_fast to make sure callers aren't confused.

This patch (of 3):

__gup_benchmark_ioctl does not handle the case where get_user_pages_fast
fails:

 - a negative return code will cause a buffer overrun

 - returning with partial success will cause use of uninitialized
   memory.

[akpm@linux-foundation.org: simplification]
Link: http://lkml.kernel.org/r/1522962072-182137-3-git-send-email-mst@redhat.com
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Andrew Morton 
Cc: Kirill A. Shutemov 
Cc: Huang Ying 
Cc: Jonathan Corbet 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Thorsten Leemhuis 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

get_user_pages_fast(): return -EFAULT on access_ok failure

2018-04-19T06:54:11+00:00

commit c61611f70958d86f659bca25c02ae69413747a8d upstream.

get_user_pages_fast is supposed to be a faster drop-in equivalent of
get_user_pages.  As such, callers expect it to return a negative return
code when passed an invalid address, and never expect it to return 0
when passed a positive number of pages, since its documentation says:

 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.

When get_user_pages_fast fall back on get_user_pages this is exactly
what happens.  Unfortunately the implementation is inconsistent: it
returns 0 if passed a kernel address, confusing callers: for example,
the following is pretty common but does not appear to do the right thing
with a kernel address:

        ret = get_user_pages_fast(addr, 1, writeable, &page);
        if (ret < 0)
                return ret;

Change get_user_pages_fast to return -EFAULT when supplied a kernel
address to make it match expectations.

All callers have been audited for consistency with the documented
semantics.

Link: http://lkml.kernel.org/r/1522962072-182137-4-git-send-email-mst@redhat.com
Fixes: 5b65c4677a57 ("mm, x86/mm: Fix performance regression in get_user_pages_fast()")
Signed-off-by: Michael S. Tsirkin 
Reported-by: syzbot+6304bf97ef436580fede@syzkaller.appspotmail.com
Reviewed-by: Andrew Morton 
Cc: Kirill A. Shutemov 
Cc: Huang Ying 
Cc: Jonathan Corbet 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Thorsten Leemhuis 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/kmemleak.c: wait for scan completion before disabling free

2018-03-28T23:42:05+00:00

A crash is observed when kmemleak_scan accesses the object->pointer,
likely due to the following race.

  TASK A             TASK B                     TASK C
  kmemleak_write
   (with "scan" and
   NOT "scan=on")
  kmemleak_scan()
                     create_object
                     kmem_cache_alloc fails
                     kmemleak_disable
                     kmemleak_do_cleanup
                     kmemleak_free_enabled = 0
                                                kfree
                                                kmemleak_free bails out
                                                 (kmemleak_free_enabled is 0)
                                                slub frees object->pointer
  update_checksum
  crash - object->pointer
   freed (DEBUG_PAGEALLOC)

kmemleak_do_cleanup waits for the scan thread to complete, but not for
direct call to kmemleak_scan via kmemleak_write.  So add a wait for
kmemleak_scan completion before disabling kmemleak_free, and while at it
fix the comment on stop_scan_thread.

[vinmenon@codeaurora.org: fix stop_scan_thread comment]
  Link: http://lkml.kernel.org/r/1522219972-22809-1-git-send-email-vinmenon@codeaurora.org
Link: http://lkml.kernel.org/r/1522063429-18992-1-git-send-email-vinmenon@codeaurora.org
Signed-off-by: Vinayak Menon 
Reviewed-by: Catalin Marinas 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memcontrol.c: fix parameter description mismatch

2018-03-28T23:42:05+00:00

There are a couple of places where parameter description and function
name do not match the actual code.  Fix it.

Link: http://lkml.kernel.org/r/1520843448-17347-1-git-send-email-honglei.wang@oracle.com
Signed-off-by: Honglei Wang 
Acked-by: Tejun Heo 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Vladimir Davydov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds