linux.git/mm/memory.c, branch v4.15

mm/memory.c: release locked page in do_swap_page()

2018-01-19T18:09:40+00:00

James reported a bug in swap paging-in from his testing.  It is that
do_swap_page doesn't release locked page so system hang-up happens due
to a deadlock on PG_locked.

It was introduced by 0bcac06f27d7 ("mm, swap: skip swapcache for swapin
of synchronous device") because I missed swap cache hit places to update
swapcache variable to work well with other logics against swapcache in
do_swap_page.

This patch fixes it.

Debugged by James Bottomley.

Link: http://lkml.kernel.org/r/<1514407817.4169.4.camel@HansenPartnership.com>
Link: http://lkml.kernel.org/r/20180102235606.GA19438@bbox
Signed-off-by: Minchan Kim 
Reported-by: James Bottomley 
Acked-by: Hugh Dickins 
Cc: Sergey Senozhatsky 
Cc: Huang Ying 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"

2017-12-16T02:53:22+00:00

This reverts commits 5c9d2d5c269c, c7da82b894e9, and e7fe7b5cae90.

We'll probably need to revisit this, but basically we should not
complicate the get_user_pages_fast() case, and checking the actual page
table protection key bits will require more care anyway, since the
protection keys depend on the exact state of the VM in question.

Particularly when doing a "remote" page lookup (ie in somebody elses VM,
not your own), you need to be much more careful than this was.  Dave
Hansen says:

 "So, the underlying bug here is that we now a get_user_pages_remote()
  and then go ahead and do the p*_access_permitted() checks against the
  current PKRU. This was introduced recently with the addition of the
  new p??_access_permitted() calls.

  We have checks in the VMA path for the "remote" gups and we avoid
  consulting PKRU for them. This got missed in the pkeys selftests
  because I did a ptrace read, but not a *write*. I also didn't
  explicitly test it against something where a COW needed to be done"

It's also not entirely clear that it makes sense to check the protection
key bits at this level at all.  But one possible eventual solution is to
make the get_user_pages_fast() case just abort if it sees protection key
bits set, which makes us fall back to the regular get_user_pages() case,
which then has a vma and can do the check there if we want to.

We'll see.

Somewhat related to this all: what we _do_ want to do some day is to
check the PAGE_USER bit - it should obviously always be set for user
pages, but it would be a good check to have back.  Because we have no
generic way to test for it, we lost it as part of moving over from the
architecture-specific x86 GUP implementation to the generic one in
commit e585513b76f7 ("x86/mm/gup: Switch GUP to the generic
get_user_page_fast() implementation").

Cc: Peter Zijlstra 
Cc: Dan Williams 
Cc: Dave Hansen 
Cc: Kirill A. Shutemov 
Cc: "Jérôme Glisse" 
Cc: Andrew Morton 
Cc: Al Viro 
Signed-off-by: Linus Torvalds

mm/memory.c: mark wp_huge_pmd() inline to prevent build failure

2017-12-15T00:00:48+00:00

With gcc 4.1.2:

    mm/memory.o: In function `wp_huge_pmd':
    memory.c:(.text+0x9b4): undefined reference to `do_huge_pmd_wp_page'

Interestingly, wp_huge_pmd() is emitted in the assembler output, but
never called.

Apparently replacing the call to pmd_write() in __handle_mm_fault() by a
call to the more complex pmd_access_permitted() reduced the ability of
the compiler to remove unused code.

Fix this by marking wp_huge_pmd() inline, like was done in commit
91a90140f998 ("mm/memory.c: mark create_huge_pmd() inline to prevent
build failure") for a similar problem.

[akpm@linux-foundation.org: add comment]
Link: http://lkml.kernel.org/r/1512335500-10889-1-git-send-email-geert@linux-m68k.org
Fixes: c7da82b894e9eef6 ("mm: replace pmd_write with pmd_access_permitted in fault + gup paths")
Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2017-11-30T03:12:44+00:00

Mergr misc fixes from Andrew Morton:
 "28 fixes"

* emailed patches from Andrew Morton : (28 commits)
  fs/hugetlbfs/inode.c: change put_page/unlock_page order in hugetlbfs_fallocate()
  mm/hugetlb: fix NULL-pointer dereference on 5-level paging machine
  autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored"
  autofs: revert "autofs: take more care to not update last_used on path walk"
  fs/fat/inode.c: fix sb_rdonly() change
  mm, memcg: fix mem_cgroup_swapout() for THPs
  mm: migrate: fix an incorrect call of prep_transhuge_page()
  kmemleak: add scheduling point to kmemleak_scan()
  scripts/bloat-o-meter: don't fail with division by 0
  fs/mbcache.c: make count_objects() more robust
  Revert "mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical"
  mm/madvise.c: fix madvise() infinite loop under special circumstances
  exec: avoid RLIMIT_STACK races with prlimit()
  IB/core: disable memory registration of filesystem-dax vmas
  v4l2: disable filesystem-dax mapping support
  mm: fail get_vaddr_frames() for filesystem-dax mappings
  mm: introduce get_user_pages_longterm
  device-dax: implement ->split() to catch invalid munmap attempts
  mm, hugetlbfs: introduce ->split() to vm_operations_struct
  scripts/faddr2line: extend usage on generic arch
  ...

mm: replace pte_write with pte_access_permitted in fault + gup paths

2017-11-30T02:40:42+00:00

The 'access_permitted' helper is used in the gup-fast path and goes
beyond the simple _PAGE_RW check to also:

 - validate that the mapping is writable from a protection keys
   standpoint

 - validate that the pte has _PAGE_USER set since all fault paths where
   pte_write is must be referencing user-memory.

Link: http://lkml.kernel.org/r/151043111604.2842.8051684481794973100.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams 
Cc: Dave Hansen 
Cc: Kirill A. Shutemov 
Cc: "Jérôme Glisse" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace pmd_write with pmd_access_permitted in fault + gup paths

2017-11-30T02:40:42+00:00

The 'access_permitted' helper is used in the gup-fast path and goes
beyond the simple _PAGE_RW check to also:

 - validate that the mapping is writable from a protection keys
   standpoint

 - validate that the pte has _PAGE_USER set since all fault paths where
   pmd_write is must be referencing user-memory.

Link: http://lkml.kernel.org/r/151043111049.2842.15241454964150083466.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams 
Cc: Dave Hansen 
Cc: Kirill A. Shutemov 
Cc: "Jérôme Glisse" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace pud_write with pud_access_permitted in fault + gup paths

2017-11-30T02:40:42+00:00

The 'access_permitted' helper is used in the gup-fast path and goes
beyond the simple _PAGE_RW check to also:

 - validate that the mapping is writable from a protection keys
   standpoint

 - validate that the pte has _PAGE_USER set since all fault paths where
   pud_write is must be referencing user-memory.

[dan.j.williams@intel.com: fix powerpc compile error]
  Link: http://lkml.kernel.org/r/151129127237.37405.16073414520854722485.stgit@dwillia2-desk3.amr.corp.intel.com
Link: http://lkml.kernel.org/r/151043110453.2842.2166049702068628177.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams 
Cc: Dave Hansen 
Cc: "David S. Miller" 
Cc: Kirill A. Shutemov 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "mm, thp: Do not make pmd/pud dirty without a reason"

2017-11-29T17:01:01+00:00

This reverts commit 152e93af3cfe2d29d8136cc0a02a8612507136ee.

It was a nice cleanup in theory, but as Nicolai Stange points out, we do
need to make the page dirty for the copy-on-write case even when we
didn't end up making it writable, since the dirty bit is what we use to
check that we've gone through a COW cycle.

Reported-by: Michal Hocko 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Linus Torvalds

mm, thp: Do not make pmd/pud dirty without a reason

2017-11-27T20:26:29+00:00

Currently we make page table entries dirty all the time regardless of
access type and don't even consider if the mapping is write-protected.
The reasoning is that we don't really need dirty tracking on THP and
making the entry dirty upfront may save some time on first write to the
page.

Unfortunately, such approach may result in false-positive
can_follow_write_pmd() for huge zero page or read-only shmem file.

Let's only make page dirty only if we about to write to the page anyway
(as we do for small pages).

I've restructured the code to make entry dirty inside
maybe_p[mu]d_mkwrite(). It also takes into account if the vma is
write-protected.

Signed-off-by: Kirill A. Shutemov 
Acked-by: Michal Hocko 
Cc: Hugh Dickins 
Signed-off-by: Linus Torvalds

mm: do not rely on preempt_count in print_vma_addr

2017-11-16T02:21:07+00:00

The preempt count check on print_vma_addr has been added by commit
e8bff74afbdb ("x86: fix "BUG: sleeping function called from invalid
context" in print_vma_addr()") and it relied on the elevated preempt
count from preempt_conditional_sti because preempt_count check doesn't
work on non preemptive kernels by default.

The code has evolved though and commit d99e1bd175f4 ("x86/entry/traps:
Refactor preemption and interrupt flag handling") has replaced
preempt_conditional_sti by an explicit preempt_disable which is noop on
!PREEMPT so the check in print_vma_addr is broken.

Fix the issue by using trylock on mmap_sem rather than chacking the
preempt count.  The allocation we are relying on has to be GFP_NOWAIT as
well.  There is a chance that we won't dump the vma state if the lock is
contended or the memory short but this is acceptable outcome and much
less fragile than the not working preemption check or tricks around it.

Link: http://lkml.kernel.org/r/20171106134031.g6dbelg55mrbyc6i@dhcp22.suse.cz
Fixes: d99e1bd175f4 ("x86/entry/traps: Refactor preemption and interrupt flag handling")
Signed-off-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Acked-by: Yang Shi 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds