linux-stable.git/include/linux/mm.h, branch v5.1.2

Merge branch 'page-refs' (page ref overflow)

2019-04-14T22:09:40+00:00

Merge page ref overflow branch.

Jann Horn reported that he can overflow the page ref count with
sufficient memory (and a filesystem that is intentionally extremely
slow).

Admittedly it's not exactly easy.  To have more than four billion
references to a page requires a minimum of 32GB of kernel memory just
for the pointers to the pages, much less any metadata to keep track of
those pointers.  Jann needed a total of 140GB of memory and a specially
crafted filesystem that leaves all reads pending (in order to not ever
free the page references and just keep adding more).

Still, we have a fairly straightforward way to limit the two obvious
user-controllable sources of page references: direct-IO like page
references gotten through get_user_pages(), and the splice pipe page
duplication.  So let's just do that.

* branch page-refs:
  fs: prevent page refcount overflow in pipe_buf_get
  mm: prevent get_user_pages() from overflowing page refcount
  mm: add 'try_get_page()' helper function
  mm: make page ref count overflow check tighter and more explicit

mm: add 'try_get_page()' helper function

2019-04-14T17:00:04+00:00

This is the same as the traditional 'get_page()' function, but instead
of unconditionally incrementing the reference count of the page, it only
does so if the count was "safe".  It returns whether the reference count
was incremented (and is marked __must_check, since the caller obviously
has to be aware of it).

Also like 'get_page()', you can't use this function unless you already
had a reference to the page.  The intent is that you can use this
exactly like get_page(), but in situations where you want to limit the
maximum reference count.

The code currently does an unconditional WARN_ON_ONCE() if we ever hit
the reference count issues (either zero or negative), as a notification
that the conditional non-increment actually happened.

NOTE! The count access for the "safety" check is inherently racy, but
that doesn't matter since the buffer we use is basically half the range
of the reference count (ie we look at the sign of the count).

Acked-by: Matthew Wilcox 
Cc: Jann Horn 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

mm: make page ref count overflow check tighter and more explicit

2019-04-14T17:00:04+00:00

We have a VM_BUG_ON() to check that the page reference count doesn't
underflow (or get close to overflow) by checking the sign of the count.

That's all fine, but we actually want to allow people to use a "get page
ref unless it's already very high" helper function, and we want that one
to use the sign of the page ref (without triggering this VM_BUG_ON).

Change the VM_BUG_ON to only check for small underflows (or _very_ close
to overflowing), and ignore overflows which have strayed into negative
territory.

Acked-by: Matthew Wilcox 
Cc: Jann Horn 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

mm: refactor readahead defines in mm.h

2019-03-12T17:04:01+00:00

All users of VM_MAX_READAHEAD actually convert it to kbytes and then to
pages. Define the macro explicitly as (SZ_128K / PAGE_SIZE). This
simplifies the expression in every filesystem. Also rename the macro to
VM_READAHEAD_PAGES to properly convey its meaning. Finally remove unused
VM_MIN_READAHEAD

[akpm@linux-foundation.org: fix fs/io_uring.c, per Stephen]
Link: http://lkml.kernel.org/r/20181221144053.24318-1-nborisov@suse.com
Signed-off-by: Nikolay Borisov 
Reviewed-by: Matthew Wilcox 
Reviewed-by: David Hildenbrand 
Cc: Jens Axboe 
Cc: Eric Van Hensbergen 
Cc: Latchesar Ionkov 
Cc: Dominique Martinet 
Cc: David Howells 
Cc: Chris Mason 
Cc: Josef Bacik 
Cc: David Sterba 
Cc: Miklos Szeredi 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: create the new vm_fault_t type

2019-03-08T02:32:03+00:00

Page fault handlers are supposed to return VM_FAULT codes, but some
drivers/file systems mistakenly return error numbers.  Now that all
drivers/file systems have been converted to use the vm_fault_t return
type, change the type definition to no longer be compatible with 'int'.
By making it an unsigned int, the function prototype becomes
incompatible with a function which returns int.  Sparse will detect any
attempts to return a value which is not a VM_FAULT code.

VM_FAULT_SET_HINDEX and VM_FAULT_GET_HINDEX values are changed to avoid
conflict with other VM_FAULT codes.

[jrdr.linux@gmail.com: fix warnings]
  Link: http://lkml.kernel.org/r/20190109183742.GA24326@jordon-HP-15-Notebook-PC
Link: http://lkml.kernel.org/r/20190108183041.GA12137@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder 
Reviewed-by: William Kucharski 
Reviewed-by: Mike Rapoport 
Reviewed-by: Matthew Wilcox 
Cc: Michal Hocko 
Cc: Dan Williams 
Cc: Kirill A. Shutemov 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: update get_user_pages_longterm to migrate pages allocated from CMA region

2019-03-06T05:07:19+00:00

This patch updates get_user_pages_longterm to migrate pages allocated
out of CMA region.  This makes sure that we don't keep non-movable pages
(due to page reference count) in the CMA area.

This will be used by ppc64 in a later patch to avoid pinning pages in
the CMA region.  ppc64 uses CMA region for allocation of the hardware
page table (hash page table) and not able to migrate pages out of CMA
region results in page table allocation failures.

One case where we hit this easy is when a guest using a VFIO passthrough
device.  VFIO locks all the guest's memory and if the guest memory is
backed by CMA region, it becomes unmovable resulting in fragmenting the
CMA and possibly preventing other guests from allocation a large enough
hash page table.

NOTE: We allocate the new page without using __GFP_THISNODE

Link: http://lkml.kernel.org/r/20190114095438.32470-3-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Cc: Alexey Kardashevskiy 
Cc: Andrea Arcangeli 
Cc: David Gibson 
Cc: Michael Ellerman 
Cc: Michal Hocko 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs: don't open code lru_to_page()

2019-01-04T21:13:48+00:00

Multiple filesystems open code lru_to_page().  Rectify this by moving
the macro from mm_inline (which is specific to lru stuff) to the more
generic mm.h header and start using the macro where appropriate.

No functional changes.

Link: http://lkml.kernel.org/r/20181129104810.23361-1-nborisov@suse.com
Link: https://lkml.kernel.org/r/20181129075301.29087-1-nborisov@suse.com
Signed-off-by: Nikolay Borisov 
Acked-by: Michal Hocko 
Reviewed-by: David Hildenbrand 
Reviewed-by: Mike Rapoport 
Acked-by: Pankaj gupta 
Acked-by: "Yan, Zheng" 		[ceph]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: treewide: remove unused address argument from pte_alloc functions

2019-01-04T21:13:47+00:00

Patch series "Add support for fast mremap".

This series speeds up the mremap(2) syscall by copying page tables at
the PMD level even for non-THP systems.  There is concern that the extra
'address' argument that mremap passes to pte_alloc may do something
subtle architecture related in the future that may make the scheme not
work.  Also we find that there is no point in passing the 'address' to
pte_alloc since its unused.  This patch therefore removes this argument
tree-wide resulting in a nice negative diff as well.  Also ensuring
along the way that the enabled architectures do not do anything funky
with the 'address' argument that goes unnoticed by the optimization.

Build and boot tested on x86-64.  Build tested on arm64.  The config
enablement patch for arm64 will be posted in the future after more
testing.

The changes were obtained by applying the following Coccinelle script.
(thanks Julia for answering all Coccinelle questions!).
Following fix ups were done manually:
* Removal of address argument from  pte_fragment_alloc
* Removal of pte_alloc_one_fast definitions from m68k and microblaze.

// Options: --include-headers --no-includes
// Note: I split the 'identifier fn' line, so if you are manually
// running it, please unsplit it so it runs for you.

virtual patch

@pte_alloc_func_def depends on patch exists@
identifier E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
type T2;
@@

 fn(...
- , T2 E2
 )
 { ... }

@pte_alloc_func_proto_noarg depends on patch exists@
type T1, T2, T3, T4;
identifier fn =~ "^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@

(
- T3 fn(T1, T2);
+ T3 fn(T1);
|
- T3 fn(T1, T2, T4);
+ T3 fn(T1, T2);
)

@pte_alloc_func_proto depends on patch exists@
identifier E1, E2, E4;
type T1, T2, T3, T4;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@

(
- T3 fn(T1 E1, T2 E2);
+ T3 fn(T1 E1);
|
- T3 fn(T1 E1, T2 E2, T4 E4);
+ T3 fn(T1 E1, T2 E2);
)

@pte_alloc_func_call depends on patch exists@
expression E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@

 fn(...
-,  E2
 )

@pte_alloc_macro depends on patch exists@
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
identifier a, b, c;
expression e;
position p;
@@

(
- #define fn(a, b, c) e
+ #define fn(a, b) e
|
- #define fn(a, b) e
+ #define fn(a) e
)

Link: http://lkml.kernel.org/r/20181108181201.88826-2-joelaf@google.com
Signed-off-by: Joel Fernandes (Google) 
Suggested-by: Kirill A. Shutemov 
Acked-by: Kirill A. Shutemov 
Cc: Michal Hocko 
Cc: Julia Lawall 
Cc: Kirill A. Shutemov 
Cc: William Kucharski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/mmu_notifier: use structure for invalidate_range_start/end calls v2

2018-12-28T20:11:50+00:00

To avoid having to change many call sites everytime we want to add a
parameter use a structure to group all parameters for the mmu_notifier
invalidate_range_start/end cakks.  No functional changes with this patch.

[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20181205053628.3210-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Acked-by: Christian König 
Acked-by: Jan Kara 
Cc: Matthew Wilcox 
Cc: Ross Zwisler 
Cc: Dan Williams 
Cc: Paolo Bonzini 
Cc: Radim Krcmar 
Cc: Michal Hocko 
Cc: Felix Kuehling 
Cc: Ralph Campbell 
Cc: John Hubbard 
From: Jérôme Glisse 
Subject: mm/mmu_notifier: use structure for invalidate_range_start/end calls v3

fix build warning in migrate.c when CONFIG_MMU_NOTIFIER=n

Link: http://lkml.kernel.org/r/20181213171330.8489-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove pte_lock_deinit()

2018-12-28T20:11:49+00:00

Pagetable page doesn't touch page->mapping or have any used field that
overlaps with it.  No need to clear mapping in dtor.  In fact, doing so
might mask problems that otherwise would be detected by bad_page().

Link: http://lkml.kernel.org/r/20181128235525.58780-1-yuzhao@google.com
Signed-off-by: Yu Zhao 
Reviewed-by: Matthew Wilcox 
Acked-by: Michal Hocko 
Cc: Hugh Dickins 
Cc: "Kirill A . Shutemov" 
Cc: Dan Williams 
Cc: Pavel Tatashin 
Cc: Souptick Joarder 
Cc: Logan Gunthorpe 
Cc: Keith Busch 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds