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Simplify page_is_buddy() to reduce the redundant code for better code
readability.
Signed-off-by: chenqiwu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Alexander Duyck <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Acked-by: Pankaj Gupta <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Previously if branch condition was false, the assignment was not executed.
The assignment can be safely executed even when the condition is false
and it is not incorrect as it assigns the value of 'nodemask' to
'ac.nodemask' which already has the same value.
So as the assignment can be executed unconditionally, the branch can be
removed.
Signed-off-by: Mateusz Nosek <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Use free_area_empty() API to replace list_empty() for better code
readability.
Signed-off-by: chenqiwu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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This patch makes ALLOC_KSWAPD equal to __GFP_KSWAPD_RECLAIM (cast to int).
Thanks to that code like:
if (gfp_mask & __GFP_KSWAPD_RECLAIM)
alloc_flags |= ALLOC_KSWAPD;
can be changed to:
alloc_flags |= (__force int) (gfp_mask &__GFP_KSWAPD_RECLAIM);
Thanks to this one branch less is generated in the assembly.
In case of ALLOC_KSWAPD flag two branches are saved, first one in code
that always executes in the beginning of page allocation and the second
one in loop in page allocator slowpath.
Signed-off-by: Mateusz Nosek <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Currently, the vm.min_free_kbytes sysctl value is capped at a hardcoded
64M in init_per_zone_wmark_min (unless it is overridden by khugepaged
initialization).
This value has not been modified since 2005, and enterprise-grade systems
now frequently have hundreds of GB of RAM and multiple 10, 40, or even 100
GB NICs. We have seen page allocation failures on heavily loaded systems
related to NIC drivers. These issues were resolved by an increase to
vm.min_free_kbytes.
This patch increases the hardcoded value by a factor of 4 as a temporary
solution.
Further work to make the calculation of vm.min_free_kbytes more consistent
throughout the kernel would be desirable.
As an example of the inconsistency of the current method, this value is
recalculated by init_per_zone_wmark_min() in the case of memory hotplug
which will override the value set by set_recommended_min_free_kbytes()
called during khugepaged initialization even if khugepaged remains
enabled, however an on/off toggle of khugepaged will then recalculate and
set the value via set_recommended_min_free_kbytes().
Signed-off-by: Joel Savitz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Rafael Aquini <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Test negative size in memmove in order to verify whether it correctly get
KASAN report.
Casting negative numbers to size_t would indeed turn up as a large size_t,
so it will have out-of-bounds bug and be detected by KASAN.
[[email protected]: fix -Wstringop-overflow warning]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Walter Wu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Dmitry Vyukov <[email protected]>
Reviewed-by: Andrey Ryabinin <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: kernel test robot <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Patch series "fix the missing underflow in memory operation function", v4.
The patchset helps to produce a KASAN report when size is negative in
memory operation functions. It is helpful for programmer to solve an
undefined behavior issue. Patch 1 based on Dmitry's review and
suggestion, patch 2 is a test in order to verify the patch 1.
[1]https://bugzilla.kernel.org/show_bug.cgi?id=199341
[2]https://lore.kernel.org/linux-arm-kernel/[email protected]/
This patch (of 2):
KASAN missed detecting size is a negative number in memset(), memcpy(),
and memmove(), it will cause out-of-bounds bug. So needs to be detected
by KASAN.
If size is a negative number, then it has a reason to be defined as
out-of-bounds bug type. Casting negative numbers to size_t would indeed
turn up as a large size_t and its value will be larger than ULONG_MAX/2,
so that this can qualify as out-of-bounds.
KASAN report is shown below:
BUG: KASAN: out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0
Read of size 18446744073709551608 at addr ffffff8069660904 by task cat/72
CPU: 2 PID: 72 Comm: cat Not tainted 5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x0/0x288
show_stack+0x14/0x20
dump_stack+0x10c/0x164
print_address_description.isra.9+0x68/0x378
__kasan_report+0x164/0x1a0
kasan_report+0xc/0x18
check_memory_region+0x174/0x1d0
memmove+0x34/0x88
kmalloc_memmove_invalid_size+0x70/0xa0
[1] https://bugzilla.kernel.org/show_bug.cgi?id=199341
[[email protected]: fix -Wdeclaration-after-statement warn]
Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: fix objtool warning]
Link: http://lkml.kernel.org/r/[email protected]
Reported-by: kernel test robot <[email protected]>
Reported-by: Dmitry Vyukov <[email protected]>
Suggested-by: Dmitry Vyukov <[email protected]>
Signed-off-by: Walter Wu <[email protected]>
Signed-off-by: Qian Cai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Dmitry Vyukov <[email protected]>
Reviewed-by: Andrey Ryabinin <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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When allocating memmap for hot added memory with the classic sparse, the
specified 'nid' is ignored in populate_section_memmap().
While in allocating memmap for the classic sparse during boot, the node
given by 'nid' is preferred. And VMEMMAP prefers the node of 'nid' in
both boot stage and memory hot adding. So seems no reason to not respect
the node of 'nid' for the classic sparse when hot adding memory.
Use kvmalloc_node instead to use the passed in 'nid'.
Signed-off-by: Baoquan He <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Wei Yang <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Pankaj Gupta <[email protected]>
Link: http://lkml.kernel.org/r/20200316125625.GH3486@MiWiFi-R3L-srv
Signed-off-by: Linus Torvalds <[email protected]>
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This change makes populate_section_memmap()/depopulate_section_memmap
much simpler.
Suggested-by: Michal Hocko <[email protected]>
Signed-off-by: Baoquan He <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Pankaj Gupta <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Wei Yang <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Link: http://lkml.kernel.org/r/20200316125450.GG3486@MiWiFi-R3L-srv
Signed-off-by: Linus Torvalds <[email protected]>
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After introducing mem sub section concept, pfn_present() loses its literal
meaning, and will not be necessary a truth on partial populated mem
section.
Since all of the callers use it to judge an absent section, it is better
to rename pfn_present() as pfn_in_present_section().
Signed-off-by: Pingfan Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Acked-by: Michael Ellerman <[email protected]> [powerpc]
Cc: Dan Williams <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Leonardo Bras <[email protected]>
Cc: Nathan Fontenot <[email protected]>
Cc: Nathan Lynch <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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memmap should be the address to page struct instead of address to pfn.
As mentioned by David, if system memory and devmem sit within a section,
the mismatch address would lead kdump to dump unexpected memory.
Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is valid
to get the page struct address at this point.
Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by: Wei Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Baoquan He <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Add a few simple self tests for the new flag MREMAP_DONTUNMAP, they are
simple smoke tests which also demonstrate the behavior.
[[email protected]: convert eight-spaces to hard tabs]
[[email protected]: v7]
Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: coding style fixes]
Signed-off-by: Brian Geffon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: "Michael S . Tsirkin" <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Sonny Rao <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: Jesse Barnes <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Florian Weimer <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Lokesh Gidra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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When remapping an anonymous, private mapping, if MREMAP_DONTUNMAP is set,
the source mapping will not be removed. The remap operation will be
performed as it would have been normally by moving over the page tables to
the new mapping. The old vma will have any locked flags cleared, have no
pagetables, and any userfaultfds that were watching that range will
continue watching it.
For a mapping that is shared or not anonymous, MREMAP_DONTUNMAP will cause
the mremap() call to fail. Because MREMAP_DONTUNMAP always results in
moving a VMA you MUST use the MREMAP_MAYMOVE flag, it's not possible to
resize a VMA while also moving with MREMAP_DONTUNMAP so old_len must
always be equal to the new_len otherwise it will return -EINVAL.
We hope to use this in Chrome OS where with userfaultfd we could write an
anonymous mapping to disk without having to STOP the process or worry
about VMA permission changes.
This feature also has a use case in Android, Lokesh Gidra has said that
"As part of using userfaultfd for GC, We'll have to move the physical
pages of the java heap to a separate location. For this purpose mremap
will be used. Without the MREMAP_DONTUNMAP flag, when I mremap the java
heap, its virtual mapping will be removed as well. Therefore, we'll
require performing mmap immediately after. This is not only time
consuming but also opens a time window where a native thread may call mmap
and reserve the java heap's address range for its own usage. This flag
solves the problem."
[[email protected]: v6]
Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: v7]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Brian Geffon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Lokesh Gidra <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: "Michael S . Tsirkin" <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Sonny Rao <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: Jesse Barnes <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Florian Weimer <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Even on 64 bit kernel, the mmap failure can happen for a 32 bit task.
Virtual memory space shortage of a task on mmap is reported to userspace
as -ENOMEM. It can be confused as physical memory shortage of overall
system.
The vm_unmapped_area can be called to by some drivers or other kernel core
system like filesystem. In my platform, GPU driver calls to
vm_unmapped_area and the driver returns -ENOMEM even in GPU side shortage.
It can be hard to distinguish which code layer returns the -ENOMEM.
Create mmap trace file and add trace point of vm_unmapped_area.
i.e.)
277.156599: vm_unmapped_area: addr=77e0d03000 err=0 total_vm=0x17014b flags=0x1 len=0x400000 lo=0x8000 hi=0x7878c27000 mask=0x0 ofs=0x1
342.838740: vm_unmapped_area: addr=0 err=-12 total_vm=0xffb08 flags=0x0 len=0x100000 lo=0x40000000 hi=0xfffff000 mask=0x0 ofs=0x22
[[email protected]: prefix address printk with 0x, per Matthew]
Signed-off-by: Jaewon Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Patch series "mm: mmap: add mmap trace point", v3.
Create mmap trace file and add trace point of vm_unmapped_area().
This patch (of 2):
In preparation for next patch remove inline of vm_unmapped_area and move
code to mmap.c. There is no logical change.
Also remove unmapped_area[_topdown] out of mm.h, there is no code
calling to them.
Signed-off-by: Jaewon Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Borislav Petkov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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The param "start" actually referes to the physical memory start, which is
to be mapped into virtual area vma. And it is the field vma->vm_start
which stands for the start of the area.
Most of the time, we do not read through whole implementation of a
function but only the definition and essential comments. Accurate
comments are definitely the base stone.
Signed-off-by: Wang Wenhu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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It really made me scratch my head. Replace the comment with an accurate
and consistent description.
The parameter pfn actually refers to the page frame number which is
right-shifted by PAGE_SHIFT from the physical address.
Signed-off-by: WANG Wenhu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Userfaultfd fault path was by default killable even if the caller does not
have FAULT_FLAG_KILLABLE. That makes sense before in that when with gup
we don't have FAULT_FLAG_KILLABLE properly set before. Now after previous
patch we've got FAULT_FLAG_KILLABLE applied even for gup code so it should
also make sense to let userfaultfd to honor the FAULT_FLAG_KILLABLE.
Because we're unconditionally setting FAULT_FLAG_KILLABLE in gup code
right now, this patch should have no functional change. It also cleaned
the code a little bit by introducing some helpers.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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The existing gup code does not react to the fatal signals in many code
paths. For example, in one retry path of gup we're still using
down_read() rather than down_read_killable(). Also, when doing page
faults we don't pass in FAULT_FLAG_KILLABLE as well, which means that
within the faulting process we'll wait in non-killable way as well. These
were spotted by Linus during the code review of some other patches.
Let's allow the gup code to react to fatal signals to improve the
responsiveness of threads when during gup and being killed.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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This is the gup counterpart of the change that allows the VM_FAULT_RETRY
to happen for more than once. One thing to mention is that we must check
the fatal signal here before retry because the GUP can be interrupted by
that, otherwise we can loop forever.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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The idea comes from a discussion between Linus and Andrea [1].
Before this patch we only allow a page fault to retry once. We achieved
this by clearing the FAULT_FLAG_ALLOW_RETRY flag when doing
handle_mm_fault() the second time. This was majorly used to avoid
unexpected starvation of the system by looping over forever to handle the
page fault on a single page. However that should hardly happen, and after
all for each code path to return a VM_FAULT_RETRY we'll first wait for a
condition (during which time we should possibly yield the cpu) to happen
before VM_FAULT_RETRY is really returned.
This patch removes the restriction by keeping the FAULT_FLAG_ALLOW_RETRY
flag when we receive VM_FAULT_RETRY. It means that the page fault handler
now can retry the page fault for multiple times if necessary without the
need to generate another page fault event. Meanwhile we still keep the
FAULT_FLAG_TRIED flag so page fault handler can still identify whether a
page fault is the first attempt or not.
Then we'll have these combinations of fault flags (only considering
ALLOW_RETRY flag and TRIED flag):
- ALLOW_RETRY and !TRIED: this means the page fault allows to
retry, and this is the first try
- ALLOW_RETRY and TRIED: this means the page fault allows to
retry, and this is not the first try
- !ALLOW_RETRY and !TRIED: this means the page fault does not allow
to retry at all
- !ALLOW_RETRY and TRIED: this is forbidden and should never be used
In existing code we have multiple places that has taken special care of
the first condition above by checking against (fault_flags &
FAULT_FLAG_ALLOW_RETRY). This patch introduces a simple helper to detect
the first retry of a page fault by checking against both (fault_flags &
FAULT_FLAG_ALLOW_RETRY) and !(fault_flag & FAULT_FLAG_TRIED) because now
even the 2nd try will have the ALLOW_RETRY set, then use that helper in
all existing special paths. One example is in __lock_page_or_retry(), now
we'll drop the mmap_sem only in the first attempt of page fault and we'll
keep it in follow up retries, so old locking behavior will be retained.
This will be a nice enhancement for current code [2] at the same time a
supporting material for the future userfaultfd-writeprotect work, since in
that work there will always be an explicit userfault writeprotect retry
for protected pages, and if that cannot resolve the page fault (e.g., when
userfaultfd-writeprotect is used in conjunction with swapped pages) then
we'll possibly need a 3rd retry of the page fault. It might also benefit
other potential users who will have similar requirement like userfault
write-protection.
GUP code is not touched yet and will be covered in follow up patch.
Please read the thread below for more information.
[1] https://lore.kernel.org/lkml/[email protected]/
[2] https://lore.kernel.org/lkml/[email protected]/
Suggested-by: Linus Torvalds <[email protected]>
Suggested-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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handle_userfaultfd() is currently the only one place in the kernel page
fault procedures that can respond to non-fatal userspace signals. It was
trying to detect such an allowance by checking against USER & KILLABLE
flags, which was "un-official".
In this patch, we introduced a new flag (FAULT_FLAG_INTERRUPTIBLE) to show
that the fault handler allows the fault procedure to respond even to
non-fatal signals. Meanwhile, add this new flag to the default fault
flags so that all the page fault handlers can benefit from the new flag.
With that, replacing the userfault check to this one.
Since the line is getting even longer, clean up the fault flags a bit too
to ease TTY users.
Although we've got a new flag and applied it, we shouldn't have any
functional change with this patch so far.
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Although there're tons of arch-specific page fault handlers, most of them
are still sharing the same initial value of the page fault flags. Say,
merely all of the page fault handlers would allow the fault to be retried,
and they also allow the fault to respond to SIGKILL.
Let's define a default value for the fault flags to replace those initial
page fault flags that were copied over. With this, it'll be far easier to
introduce new fault flag that can be used by all the architectures instead
of touching all the archs.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
This patch removes the risk path in handle_userfault() then we will be
sure that the callers of handle_mm_fault() will know that the VMAs might
have changed. Meanwhile with previous patch we don't lose responsiveness
as well since the core mm code now can handle the nonfatal userspace
signals even if we return VM_FAULT_RETRY.
Suggested-by: Andrea Arcangeli <[email protected]>
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Reviewed-by: Jerome Glisse <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
The idea comes from the upstream discussion between Linus and Andrea:
https://lore.kernel.org/lkml/[email protected]/
A summary to the issue: there was a special path in handle_userfault() in
the past that we'll return a VM_FAULT_NOPAGE when we detected non-fatal
signals when waiting for userfault handling. We did that by reacquiring
the mmap_sem before returning. However that brings a risk in that the
vmas might have changed when we retake the mmap_sem and even we could be
holding an invalid vma structure.
This patch is a preparation of removing that special path by allowing the
page fault to return even faster if we were interrupted by a non-fatal
signal during a user-mode page fault handling routine.
Suggested-by: Linus Torvalds <[email protected]>
Suggested-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Let SH to use the new fault_signal_pending() helper. Here we'll need to
move the up_read() out because that's actually needed as long as !RETRY
cases. At the meantime we can drop all the rest of up_read()s now (which
seems to be cleaner).
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Let powerpc code to use the new helper, by moving the signal handling
earlier before the retry logic.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Let the arm64 fault handling to use the new fault_signal_pending() helper,
by moving the signal handling out of the retry logic.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Let ARC to use the new helper fault_signal_pending() by moving the signal
check out of the retry logic as standalone. This should also helps to
simplify the code a bit.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Let's move the fatal signal check even earlier so that we can directly use
the new fault_signal_pending() in x86 mm code.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
For most architectures, we've got a quick path to detect fatal signal
after a handle_mm_fault(). Introduce a helper for that quick path.
It cleans the current codes a bit so we don't need to duplicate the same
check across archs. More importantly, this will be an unified place that
we handle the signal immediately right after an interrupted page fault, so
it'll be much easier for us if we want to change the behavior of handling
signals later on for all the archs.
Note that currently only part of the archs are using this new helper,
because some archs have their own way to handle signals. In the follow up
patches, we'll try to apply this helper to all the rest of archs.
Another note is that the "regs" parameter in the new helper is not used
yet. It'll be used very soon. Now we kept it in this patch only to avoid
touching all the archs again in the follow up patches.
[[email protected]: fix sparse warnings]
Link: http://lkml.kernel.org/r/20200311145921.GD479302@xz-x1
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
When follow_hugetlb_page() returns with *locked==0, it means we've got a
VM_FAULT_RETRY within the fauling process and we've released the mmap_sem.
When that happens, we should stop and bail out.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Patch series "mm: Page fault enhancements", v6.
This series contains cleanups and enhancements to current page fault
logic. The whole idea comes from the discussion between Andrea and Linus
on the bug reported by syzbot here:
https://lkml.org/lkml/2017/11/2/833
Basically it does two things:
(a) Allows the page fault logic to be more interactive on not only
SIGKILL, but also the rest of userspace signals, and,
(b) Allows the page fault retry (VM_FAULT_RETRY) to happen for more
than once.
For (a): with the changes we should be able to react faster when page
faults are working in parallel with userspace signals like SIGSTOP and
SIGCONT (and more), and with that we can remove the buggy part in
userfaultfd and benefit the whole page fault mechanism on faster signal
processing to reach the userspace.
For (b), we should be able to allow the page fault handler to loop for
even more than twice. Some context: for now since we have
FAULT_FLAG_ALLOW_RETRY we can allow to retry the page fault once with the
same interrupt context, however never more than twice. This can be not
only a potential cleanup to remove this assumption since AFAIU the code
itself doesn't really have this twice-only limitation (though that should
be a protective approach in the past), at the same time it'll greatly
simplify future works like userfaultfd write-protect where it's possible
to retry for more than twice (please have a look at [1] below for a
possible user that might require the page fault to be handled for a third
time; if we can remove the retry limitation we can simply drop that patch
and those complexity).
This patch (of 16):
There's plenty of places around __get_user_pages() that has a parameter
"nonblocking" which does not really mean that "it won't block" (because it
can really block) but instead it shows whether the mmap_sem is released by
up_read() during the page fault handling mostly when VM_FAULT_RETRY is
returned.
We have the correct naming in e.g. get_user_pages_locked() or
get_user_pages_remote() as "locked", however there're still many places
that are using the "nonblocking" as name.
Renaming the places to "locked" where proper to better suite the
functionality of the variable. While at it, fixing up some of the
comments accordingly.
Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Brian Geffon <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Reviewed-by: Jerome Glisse <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
The documentation currently does not include the deathless prose written
to describe functions in pagemap.h because it's not included in any rst
file. Fix up the mismatches between parameter names and the documentation
and add the file to mm-api.
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Zi Yan <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Currently the declaration and definition for is_vma_temporary_stack() are
scattered. Lets make is_vma_temporary_stack() helper available for
general use and also drop the declaration from (include/linux/huge_mm.h)
which is no longer required. While at this, rename this as
vma_is_temporary_stack() in line with existing helpers. This should not
cause any functional change.
Signed-off-by: Anshuman Khandual <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Idea of a foreign VMA with respect to the present context is very generic.
But currently there are two identical definitions for this in powerpc and
x86 platforms. Lets consolidate those redundant definitions while making
vma_is_foreign() available for general use later. This should not cause
any functional change.
Signed-off-by: Anshuman Khandual <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Patch series "mm/vma: some more minor changes", v2.
The motivation here is to consolidate VMA flags and helpers in generic
memory header and reduce code duplication when ever applicable. If there
are other possible similar instances which might be missing here, please
do let me me know. I will be happy to incorporate them.
This patch (of 3):
Move VM_NO_KHUGEPAGED into generic header (include/linux/mm.h). This just
makes sure that no VMA flag is scattered in individual function files any
longer. While at this, fix an old comment which is no longer valid. This
should not cause any functional change.
Signed-off-by: Anshuman Khandual <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
Following the update of pagewalk code commit a07984d48146 ("mm: pagewalk:
add p4d_entry() and pgd_entry()") we can modify the mapping_dirty_helpers'
huge page-table entry callbacks to avoid splitting when a huge pud or -pmd
is encountered.
Signed-off-by: Thomas Hellstrom <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Steven Price <[email protected]>
Cc: Andrew Morton <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
If a task is getting moved out of the OOMing cgroup, it might result in
unexpected OOM killings if memory.oom.group is used anywhere in the cgroup
tree.
Imagine the following example:
A (oom.group = 1)
/ \
(OOM) B C
Let's say B's memory.max is exceeded and it's OOMing. The OOM killer
selects a task in B as a victim, but someone asynchronously moves the task
into C. mem_cgroup_get_oom_group() will iterate over all ancestors of C
up to the root cgroup. In theory it had to stop at the oom_domain level -
the memory cgroup which is OOMing. But because B is not an ancestor of C,
it's not happening. Instead it chooses A (because it's oom.group is set),
and kills all tasks in A. This behavior is wrong because the OOM happened
in B, so there is no reason to kill anything outside.
Fix this by checking it the memory cgroup to which the task belongs is a
descendant of the oom_domain. If not, memory.oom.group should be ignored,
and the OOM killer should kill only the victim task.
Reported-by: Dan Schatzberg <[email protected]>
Signed-off-by: Roman Gushchin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
|
|
The read side of this is all protected, but we can still tear if multiple
iterations of mem_cgroup_protected are going at the same time.
There's some intentional racing in mem_cgroup_protected which is ok, but
load/store tearing should be avoided.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/d1e9fbc0379fe8db475d82c8b6fbe048876e12ae.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
|
|
The write side of this is xchg()/smp_mb(), so that's all good. Just a few
sites missing a READ_ONCE.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/bbec2c3d822217334855c8877a9d28b2a6d395fb.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
|
|
This can be set concurrently with reads, which may cause the wrong value
to be propagated.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
|
|
This can be set concurrently with reads, which may cause the wrong value
to be propagated.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
|
|
This one is a bit more nuanced because we have memcg_max_mutex, which is
mostly just used for enforcing invariants, but we still need to READ_ONCE
since (despite its name) it doesn't really protect memory.max access.
On write (page_counter_set_max() and memory_max_write()) we use xchg(),
which uses smp_mb(), so that's already fine.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/50a31e5f39f8ae6c8fb73966ba1455f0924e8f44.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
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A mem_cgroup's high attribute can be concurrently set at the same time as
we are trying to read it -- for example, if we are in memory_high_write at
the same time as we are trying to do high reclaim.
Signed-off-by: Chris Down <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Link: http://lkml.kernel.org/r/2f66f7038ed1d4688e59de72b627ae0ea52efa83.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <[email protected]>
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mem_cgroup_id_get_many() is currently used only when MMU or MEMCG_SWAP
configuration options are enabled. Having them disabled triggers the
following warning at compile time:
linux/mm/memcontrol.c:4797:13: warning: `mem_cgroup_id_get_many' defined but not used [-Wunused-function]
static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
Make mem_cgroup_id_get_many() __maybe_unused to address the issue.
Signed-off-by: Vincenzo Frascino <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Chris Down <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Currently multiple locations in memcg code, css_tryget_online() is being
used. However it doesn't matter whether the cgroup is online for the
callers. Online used to matter when we had reparenting on offlining and
we needed a way to prevent new ones from showing up.
The failure case for couple of these css_tryget_online usage is to
fallback to root_mem_cgroup which kind of make bypassing the memcg
limits possible for some workloads. For example creating an inotify
group in a subcontainer and then deleting that container after moving the
process to a different container will make all the event objects
allocated for that group to the root_mem_cgroup. So, using
css_tryget_online() is dangerous for such cases.
Two locations still use the online version. The swapin of offlined
memcg's pages and the memcg kmem cache creation. The kmem cache indeed
needs the online version as the kernel does the reparenting of memcg
kmem caches. For the swapin case, it has been left for later as the
fallback is not really that concerning.
With swap accounting enabled, if the memcg of the swapped out page is
not online then the memcg extracted from the given 'mm' will be charged
and if 'mm' is NULL then root memcg will be charged. However I could
not find a code path where the given 'mm' will be NULL for swap-in
case.
Signed-off-by: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Roman Gushchin <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Right now, the effective protection of any given cgroup is capped by its
own explicit memory.low setting, regardless of what the parent says. The
reasons for this are mostly historical and ease of implementation: to make
delegation of memory.low safe, effective protection is the min() of all
memory.low up the tree.
Unfortunately, this limitation makes it impossible to protect an entire
subtree from another without forcing the user to make explicit protection
allocations all the way to the leaf cgroups - something that is highly
undesirable in real life scenarios.
Consider memory in a data center host. At the cgroup top level, we have a
distinction between system management software and the actual workload the
system is executing. Both branches are further subdivided into individual
services, job components etc.
We want to protect the workload as a whole from the system management
software, but that doesn't mean we want to protect and prioritize
individual workload wrt each other. Their memory demand can vary over
time, and we'd want the VM to simply cache the hottest data within the
workload subtree. Yet, the current memory.low limitations force us to
allocate a fixed amount of protection to each workload component in order
to get protection from system management software in general. This
results in very inefficient resource distribution.
Another concern with mandating downward allocation is that, as the
complexity of the cgroup tree grows, it gets harder for the lower levels
to be informed about decisions made at the host-level. Consider a
container inside a namespace that in turn creates its own nested tree of
cgroups to run multiple workloads. It'd be extremely difficult to
configure memory.low parameters in those leaf cgroups that on one hand
balance pressure among siblings as the container desires, while also
reflecting the host-level protection from e.g. rpm upgrades, that lie
beyond one or more delegation and namespacing points in the tree.
It's highly unusual from a cgroup interface POV that nested levels have to
be aware of and reflect decisions made at higher levels for them to be
effective.
To enable such use cases and scale configurability for complex trees, this
patch implements a resource inheritance model for memory that is similar
to how the CPU and the IO controller implement work-conserving resource
allocations: a share of a resource allocated to a subree always applies to
the entire subtree recursively, while allowing, but not mandating,
children to further specify distribution rules.
That means that if protection is explicitly allocated among siblings,
those configured shares are being followed during page reclaim just like
they are now. However, if the memory.low set at a higher level is not
fully claimed by the children in that subtree, the "floating" remainder is
applied to each cgroup in the tree in proportion to its size. Since
reclaim pressure is applied in proportion to size as well, each child in
that tree gets the same boost, and the effect is neutral among siblings -
with respect to each other, they behave as if no memory control was
enabled at all, and the VM simply balances the memory demands optimally
within the subtree. But collectively those cgroups enjoy a boost over the
cgroups in neighboring trees.
E.g. a leaf cgroup with a memory.low setting of 0 no longer means that
it's not getting a share of the hierarchically assigned resource, just
that it doesn't claim a fixed amount of it to protect from its siblings.
This allows us to recursively protect one subtree (workload) from another
(system management), while letting subgroups compete freely among each
other - without having to assign fixed shares to each leaf, and without
nested groups having to echo higher-level settings.
The floating protection composes naturally with fixed protection.
Consider the following example tree:
A A: low = 2G
/ \ A1: low = 1G
A1 A2 A2: low = 0G
As outside pressure is applied to this tree, A1 will enjoy a fixed
protection from A2 of 1G, but the remaining, unclaimed 1G from A is split
evenly among A1 and A2, coming out to 1.5G and 0.5G.
There is a slight risk of regressing theoretical setups where the
top-level cgroups don't know about the true budgeting and set bogusly high
"bypass" values that are meaningfully allocated down the tree. Such
setups would rely on unclaimed protection to be discarded, and
distributing it would change the intended behavior. Be safe and hide the
new behavior behind a mount option, 'memory_recursiveprot'.
Signed-off-by: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Chris Down <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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The effective protection of any given cgroup is a somewhat complicated
construct that depends on the ancestor's configuration, siblings'
configurations, as well as current memory utilization in all these groups.
It's done this way to satisfy hierarchical delegation requirements while
also making the configuration semantics flexible and expressive in complex
real life scenarios.
Unfortunately, all the rules and requirements are sparsely documented, and
the code is a little too clever in merging different scenarios into a
single min() expression. This makes it hard to reason about the
implementation and avoid breaking semantics when making changes to it.
This patch documents each semantic rule individually and splits out the
handling of the overcommit case from the regular case.
Michal Koutný also points out that the points of equilibrium as described
in the existing example scenarios aren't actually accurate. Delete these
examples for now to avoid confusion.
Signed-off-by: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Chris Down <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Patch series "mm: memcontrol: recursive memory.low protection", v3.
The current memory.low (and memory.min) semantics require protection to be
assigned to a cgroup in an untinterrupted chain from the top-level cgroup
all the way to the leaf.
In practice, we want to protect entire cgroup subtrees from each other
(system management software vs. workload), but we would like the VM to
balance memory optimally *within* each subtree, without having to make
explicit weight allocations among individual components. The current
semantics make that impossible.
They also introduce unmanageable complexity into more advanced resource
trees. For example:
host root
`- system.slice
`- rpm upgrades
`- logging
`- workload.slice
`- a container
`- system.slice
`- workload.slice
`- job A
`- component 1
`- component 2
`- job B
At a host-level perspective, we would like to protect the outer
workload.slice subtree as a whole from rpm upgrades, logging etc. But for
that to be effective, right now we'd have to propagate it down through the
container, the inner workload.slice, into the job cgroup and ultimately
the component cgroups where memory is actually, physically allocated.
This may cross several tree delegation points and namespace boundaries,
which make such a setup near impossible.
CPU and IO on the other hand are already distributed recursively. The
user would simply configure allowances at the host level, and they would
apply to the entire subtree without any downward propagation.
To enable the above-mentioned usecases and bring memory in line with other
resource controllers, this patch series extends memory.low/min such that
settings apply recursively to the entire subtree. Users can still assign
explicit shares in subgroups, but if they don't, any ancestral protection
will be distributed such that children compete freely amongst each other -
as if no memory control were enabled inside the subtree - but enjoy
protection from neighboring trees.
In the above example, the user would then be able to configure shares of
CPU, IO and memory at the host level to comprehensively protect and
isolate the workload.slice as a whole from system.slice activity.
Patch #1 fixes an existing bug that can give a cgroup tree more protection
than it should receive as per ancestor configuration.
Patch #2 simplifies and documents the existing code to make it easier to
reason about the changes in the next patch.
Patch #3 finally implements recursive memory protection semantics.
Because of a risk of regressing legacy setups, the new semantics are
hidden behind a cgroup2 mount option, 'memory_recursiveprot'.
More details in patch #3.
This patch (of 3):
When memory.low is overcommitted - i.e. the children claim more
protection than their shared ancestor grants them - the allowance is
distributed in proportion to how much each sibling uses their own declared
protection:
low_usage = min(memory.low, memory.current)
elow = parent_elow * (low_usage / siblings_low_usage)
However, siblings_low_usage is not the sum of all low_usages. It sums
up the usages of *only those cgroups that are within their memory.low*
That means that low_usage can be *bigger* than siblings_low_usage, and
consequently the total protection afforded to the children can be
bigger than what the ancestor grants the subtree.
Consider three groups where two are in excess of their protection:
A/memory.low = 10G
A/A1/memory.low = 10G, memory.current = 20G
A/A2/memory.low = 10G, memory.current = 20G
A/A3/memory.low = 10G, memory.current = 8G
siblings_low_usage = 8G (only A3 contributes)
A1/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(8G) = 12.5G -> 10G
A2/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(8G) = 12.5G -> 10G
A3/elow = parent_elow(10G) * low_usage(8G) / siblings_low_usage(8G) = 10.0G
(the 12.5G are capped to the explicit memory.low setting of 10G)
With that, the sum of all awarded protection below A is 30G, when A
only grants 10G for the entire subtree.
What does this mean in practice? A1 and A2 would still be in excess of
their 10G allowance and would be reclaimed, whereas A3 would not. As
they eventually drop below their protection setting, they would be
counted in siblings_low_usage again and the error would right itself.
When reclaim was applied in a binary fashion (cgroup is reclaimed when
it's above its protection, otherwise it's skipped) this would actually
work out just fine. However, since 1bc63fb1272b ("mm, memcg: make scan
aggression always exclude protection"), reclaim pressure is scaled to
how much a cgroup is above its protection. As a result this
calculation error unduly skews pressure away from A1 and A2 toward the
rest of the system.
But why did we do it like this in the first place?
The reasoning behind exempting groups in excess from
siblings_low_usage was to go after them first during reclaim in an
overcommitted subtree:
A/memory.low = 2G, memory.current = 4G
A/A1/memory.low = 3G, memory.current = 2G
A/A2/memory.low = 1G, memory.current = 2G
siblings_low_usage = 2G (only A1 contributes)
A1/elow = parent_elow(2G) * low_usage(2G) / siblings_low_usage(2G) = 2G
A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G
While the children combined are overcomitting A and are technically
both at fault, A2 is actively declaring unprotected memory and we
would like to reclaim that first.
However, while this sounds like a noble goal on the face of it, it
doesn't make much difference in actual memory distribution: Because A
is overcommitted, reclaim will not stop once A2 gets pushed back to
within its allowance; we'll have to reclaim A1 either way. The end
result is still that protection is distributed proportionally, with A1
getting 3/4 (1.5G) and A2 getting 1/4 (0.5G) of A's allowance.
[ If A weren't overcommitted, it wouldn't make a difference since each
cgroup would just get the protection it declares:
A/memory.low = 2G, memory.current = 3G
A/A1/memory.low = 1G, memory.current = 1G
A/A2/memory.low = 1G, memory.current = 2G
With the current calculation:
siblings_low_usage = 1G (only A1 contributes)
A1/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(1G) = 2G -> 1G
A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(1G) = 2G -> 1G
Including excess groups in siblings_low_usage:
siblings_low_usage = 2G
A1/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G -> 1G
A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G -> 1G ]
Simplify the calculation and fix the proportional reclaim bug by
including excess cgroups in siblings_low_usage.
After this patch, the effective memory.low distribution from the
example above would be as follows:
A/memory.low = 10G
A/A1/memory.low = 10G, memory.current = 20G
A/A2/memory.low = 10G, memory.current = 20G
A/A3/memory.low = 10G, memory.current = 8G
siblings_low_usage = 28G
A1/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(28G) = 3.5G
A2/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(28G) = 3.5G
A3/elow = parent_elow(10G) * low_usage(8G) / siblings_low_usage(28G) = 2.8G
Fixes: 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection")
Fixes: 230671533d64 ("mm: memory.low hierarchical behavior")
Signed-off-by: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Chris Down <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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