Using MAX_INPUT_BUF_SZ as the maximum length of the string makes fortify
complain as it thinks the string might be longer than the buffer, and if
it is, we will end up with a "string" that is missing a NUL terminator.
It's trivial to show that 'tok' points to a NUL-terminated string which is
less than MAX_INPUT_BUF_SZ in length, so we may as well just use strcpy()
and avoid the warning.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Cc: Mike Kravetz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
When the THP NUMA fault support was added THP migration was not supported
yet. So the ad hoc THP migration was implemented in NUMA fault handling.
Since v4.14 THP migration has been supported so it doesn't make too much
sense to still keep another THP migration implementation rather than using
the generic migration code.
This patch reworks the NUMA fault handling to use generic migration
implementation to migrate misplaced page. There is no functional change.
After the refactor the flow of NUMA fault handling looks just like its
PTE counterpart:
Acquire ptl
Prepare for migration (elevate page refcount)
Release ptl
Isolate page from lru and elevate page refcount
Migrate the misplaced THP
If migration fails just restore the old normal PMD.
In the old code anon_vma lock was needed to serialize THP migration
against THP split, but since then the THP code has been reworked a lot, it
seems anon_vma lock is not required anymore to avoid the race.
The page refcount elevation when holding ptl should prevent from THP
split.
Use migrate_misplaced_page() for both base page and THP NUMA hinting fault
and remove all the dead and duplicate code.
[[email protected]: fix a double unlock bug]
Link: https://lkml.kernel.org/r/YLX8uYN01JmfLnlK@mwanda
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Shi <[email protected]>
Signed-off-by: Dan Carpenter <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Pach series "mm: thp: use generic THP migration for NUMA hinting fault", v3.
When the THP NUMA fault support was added THP migration was not supported
yet. So the ad hoc THP migration was implemented in NUMA fault handling.
Since v4.14 THP migration has been supported so it doesn't make too much
sense to still keep another THP migration implementation rather than using
the generic migration code. It is definitely a maintenance burden to keep
two THP migration implementation for different code paths and it is more
error prone. Using the generic THP migration implementation allows us
remove the duplicate code and some hacks needed by the old ad hoc
implementation.
A quick grep shows x86_64, PowerPC (book3s), ARM64 ans S390 support both
THP and NUMA balancing. The most of them support THP migration except for
S390. Zi Yan tried to add THP migration support for S390 before but it
was not accepted due to the design of S390 PMD. For the discussion,
please see: https://lkml.org/lkml/2018/4/27/953.
Per the discussion with Gerald Schaefer in v1 it is acceptible to skip
huge PMD for S390 for now.
I saw there were some hacks about gup from git history, but I didn't
figure out if they have been removed or not since I just found FOLL_NUMA
code in the current gup implementation and they seems useful.
Patch #1 ~ #2 are preparation patches.
Patch #3 is the real meat.
Patch #4 ~ #6 keep consistent counters and behaviors with before.
Patch #7 skips change huge PMD to prot_none if thp migration is not supported.
Test
----
Did some tests to measure the latency of do_huge_pmd_numa_page. The test
VM has 80 vcpus and 64G memory. The test would create 2 processes to
consume 128G memory together which would incur memory pressure to cause
THP splits. And it also creates 80 processes to hog cpu, and the memory
consumer processes are bound to different nodes periodically in order to
increase NUMA faults.
The below test script is used:
echo 3 > /proc/sys/vm/drop_caches
# Run stress-ng for 24 hours
./stress-ng/stress-ng --vm 2 --vm-bytes 64G --timeout 24h &
PID=$!
./stress-ng/stress-ng --cpu $NR_CPUS --timeout 24h &
# Wait for vm stressors forked
sleep 5
PID_1=`pgrep -P $PID | awk 'NR == 1'`
PID_2=`pgrep -P $PID | awk 'NR == 2'`
JOB1=`pgrep -P $PID_1`
JOB2=`pgrep -P $PID_2`
# Bind load jobs to different nodes periodically to force generate
# cross node memory access
while [ -d "/proc/$PID" ]
do
taskset -apc 8 $JOB1
taskset -apc 8 $JOB2
sleep 300
taskset -apc 58 $JOB1
taskset -apc 58 $JOB2
sleep 300
done
With the above test the histogram of latency of do_huge_pmd_numa_page is
as shown below. Since the number of do_huge_pmd_numa_page varies
drastically for each run (should be due to scheduler), so I converted the
raw number to percentage.
patched base
@us[stress-ng]:
[0] 3.57% 0.16%
[1] 55.68% 18.36%
[2, 4) 10.46% 40.44%
[4, 8) 7.26% 17.82%
[8, 16) 21.12% 13.41%
[16, 32) 1.06% 4.27%
[32, 64) 0.56% 4.07%
[64, 128) 0.16% 0.35%
[128, 256) < 0.1% < 0.1%
[256, 512) < 0.1% < 0.1%
[512, 1K) < 0.1% < 0.1%
[1K, 2K) < 0.1% < 0.1%
[2K, 4K) < 0.1% < 0.1%
[4K, 8K) < 0.1% < 0.1%
[8K, 16K) < 0.1% < 0.1%
[16K, 32K) < 0.1% < 0.1%
[32K, 64K) < 0.1% < 0.1%
Per the result, patched kernel is even slightly better than the base
kernel. I think this is because the lock contention against THP split is
less than base kernel due to the refactor.
To exclude the affect from THP split, I also did test w/o memory pressure.
No obvious regression is spotted. The below is the test result *w/o*
memory pressure.
patched base
@us[stress-ng]:
[0] 7.97% 18.4%
[1] 69.63% 58.24%
[2, 4) 4.18% 2.63%
[4, 8) 0.22% 0.17%
[8, 16) 1.03% 0.92%
[16, 32) 0.14% < 0.1%
[32, 64) < 0.1% < 0.1%
[64, 128) < 0.1% < 0.1%
[128, 256) < 0.1% < 0.1%
[256, 512) 0.45% 1.19%
[512, 1K) 15.45% 17.27%
[1K, 2K) < 0.1% < 0.1%
[2K, 4K) < 0.1% < 0.1%
[4K, 8K) < 0.1% < 0.1%
[8K, 16K) 0.86% 0.88%
[16K, 32K) < 0.1% 0.15%
[32K, 64K) < 0.1% < 0.1%
[64K, 128K) < 0.1% < 0.1%
[128K, 256K) < 0.1% < 0.1%
The series also survived a series of tests that exercise NUMA balancing
migrations by Mel.
This patch (of 7):
Add orig_pmd to struct vm_fault so the "orig_pmd" parameter used by huge
page fault could be removed, just like its PTE counterpart does.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Shi <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Transparent huge pages are supported for read-only non-shmem files, but
are only used for vmas with VM_DENYWRITE. This condition ensures that
file THPs are protected from writes while an application is running
(ETXTBSY). Any existing file THPs are then dropped from the page cache
when a file is opened for write in do_dentry_open(). Since sys_mmap
ignores MAP_DENYWRITE, this constrains the use of file THPs to vmas
produced by execve().
Systems that make heavy use of shared libraries (e.g. Android) are unable
to apply VM_DENYWRITE through the dynamic linker, preventing them from
benefiting from the resultant reduced contention on the TLB.
This patch reduces the constraint on file THPs allowing use with any
executable mapping from a file not opened for write (see
inode_is_open_for_write()). It also introduces additional conditions to
ensure that files opened for write will never be backed by file THPs.
Restricting the use of THPs to executable mappings eliminates the risk
that a read-only file later opened for write would encounter significant
latencies due to page cache truncation.
The ld linker flag '-z max-page-size=(hugepage size)' can be used to
produce executables with the necessary layout. The dynamic linker must
map these file's segments at a hugepage size aligned vma for the mapping
to be backed with THPs.
Comparison of the performance characteristics of 4KB and 2MB-backed
libraries follows; the Android dex2oat tool was used to AOT compile an
example application on a single ARM core.
4KB Pages:
==========
count event_name # count / runtime
598,995,035,942 cpu-cycles # 1.800861 GHz
81,195,620,851 raw-stall-frontend # 244.112 M/sec
347,754,466,597 iTLB-loads # 1.046 G/sec
2,970,248,900 iTLB-load-misses # 0.854122% miss rate
Total test time: 332.854998 seconds.
2MB Pages:
==========
count event_name # count / runtime
592,872,663,047 cpu-cycles # 1.800358 GHz
76,485,624,143 raw-stall-frontend # 232.261 M/sec
350,478,413,710 iTLB-loads # 1.064 G/sec
803,233,322 iTLB-load-misses # 0.229182% miss rate
Total test time: 329.826087 seconds
A check of /proc/$(pidof dex2oat64)/smaps shows THPs in use:
/apex/com.android.art/lib64/libart.so
FilePmdMapped: 4096 kB
/apex/com.android.art/lib64/libart-compiler.so
FilePmdMapped: 2048 kB
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Collin Fijalkovich <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Reviewed-by: William Kucharski <[email protected]>
Acked-by: Song Liu <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Hridya Valsaraju <[email protected]>
Cc: Kalesh Singh <[email protected]>
Cc: Tim Murray <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Alexander Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Since commit d6995da311 ("hugetlb: use page.private for hugetlb specific
page flags") converts page.private for hugetlb specific page flags. We
should use hugetlb_page_subpool() to get the subpool pointer instead of
page_private().
This 'could' prevent the migration of hugetlb pages. page_private(hpage)
is now used for hugetlb page specific flags. At migration time, the only
flag which could be set is HPageVmemmapOptimized. This flag will only be
set if the new vmemmap reduction feature is enabled. In addition,
!page_mapping() implies an anonymous mapping. So, this will prevent
migration of hugetb pages in anonymous mappings if the vmemmap reduction
feature is enabled.
In addition, that if statement checked for the rare race condition of a
page being migrated while in the process of being freed. Since that check
is now wrong, we could leak hugetlb subpool usage counts.
The commit forgot to update it in the page migration routine. So fix it.
[[email protected]: fix compiler error when !CONFIG_HUGETLB_PAGE reported by Randy]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: d6995da311 ("hugetlb: use page.private for hugetlb specific page flags")
Signed-off-by: Muchun Song <[email protected]>
Reported-by: Anshuman Khandual <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Tested-by: Anshuman Khandual <[email protected]> [arm64]
Cc: Oscar Salvador <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Xiongchun Duan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
CONFIG_SPARSEMEM_VMEMMAP is now the only available memory model on arm64
platforms and free_unused_memmap() would just return without creating any
holes in the memmap mapping. There is no need for any special handling in
pfn_valid() and HAVE_ARCH_PFN_VALID can just be dropped. This also moves
the pfn upper bits sanity check into generic pfn_valid().
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Anshuman Khandual <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Mike Rapoport <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
The arm64's version of pfn_valid() differs from the generic because of two
reasons:
* Parts of the memory map are freed during boot. This makes it necessary to
verify that there is actual physical memory that corresponds to a pfn
which is done by querying memblock.
* There are NOMAP memory regions. These regions are not mapped in the
linear map and until the previous commit the struct pages representing
these areas had default values.
As the consequence of absence of the special treatment of NOMAP regions in
the memory map it was necessary to use memblock_is_map_memory() in
pfn_valid() and to have pfn_valid_within() aliased to pfn_valid() so that
generic mm functionality would not treat a NOMAP page as a normal page.
Since the NOMAP regions are now marked as PageReserved(), pfn walkers and
the rest of core mm will treat them as unusable memory and thus
pfn_valid_within() is no longer required at all and can be disabled on
arm64.
pfn_valid() can be slightly simplified by replacing
memblock_is_map_memory() with memblock_is_memory().
[[email protected]: fix merge fix]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
The intended semantics of pfn_valid() is to verify whether there is a
struct page for the pfn in question and nothing else.
Yet, on arm64 it is used to distinguish memory areas that are mapped in
the linear map vs those that require ioremap() to access them.
Introduce a dedicated pfn_is_map_memory() wrapper for
memblock_is_map_memory() to perform such check and use it where
appropriate.
Using a wrapper allows to avoid cyclic include dependencies.
While here also update style of pfn_valid() so that both pfn_valid() and
pfn_is_map_memory() declarations will be consistent.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
The struct pages representing a reserved memory region are initialized
using reserve_bootmem_range() function. This function is called for each
reserved region just before the memory is freed from memblock to the buddy
page allocator.
The struct pages for MEMBLOCK_NOMAP regions are kept with the default
values set by the memory map initialization which makes it necessary to
have a special treatment for such pages in pfn_valid() and
pfn_valid_within().
Split out initialization of the reserved pages to a function with a
meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the
reserved regions and mark struct pages for the NOMAP regions as
PageReserved.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Patch series "arm64: drop pfn_valid_within() and simplify pfn_valid()", v4.
These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire
pfn_valid_within() to 1.
The idea is to mark NOMAP pages as reserved in the memory map and restore
the intended semantics of pfn_valid() to designate availability of struct
page for a pfn.
With this the core mm will be able to cope with the fact that it cannot
use NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER
blocks will be treated correctly even without the need for
pfn_valid_within.
This patch (of 4):
Add comment describing the semantics of pfn_valid() that clarifies that
pfn_valid() only checks for availability of a memory map entry (i.e.
struct page) for a PFN rather than availability of usable memory backing
that PFN.
The most "generic" version of pfn_valid() used by the configurations with
SPARSEMEM enabled resides in include/linux/mmzone.h so this is the most
suitable place for documentation about semantics of pfn_valid().
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Suggested-by: Anshuman Khandual <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
When trying to migrate pages to obey mempolicy, the huge zero page is
split by inserting base zero pfn to all PTEs, then the page table walk
fallback to PTE level and just skips zero page. Skipping zero page for
mempolicy has been the behavior of kernel since v2.6.16 due to commit
f4598c8b36 ("[PATCH] migration: make sure there is no attempt to migrate
reserved pages."). So it seems pointless to split huge zero page, it
could be just skipped like base zero page.
Set ACTION_CONTINUE to prevent the walk_page_range() split the pmd for
this case.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Shi <[email protected]>
Reviewed-by: Zi Yan <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
MPOL_LOCAL policy has been setup as a real policy, but it is still handled
like a faked POL_PREFERRED policy with one internal MPOL_F_LOCAL flag bit
set, and there are many places having to judge the real 'prefer' or the
'local' policy, which are quite confusing.
In current code, there are 4 cases that MPOL_LOCAL are used:
1. user specifies 'local' policy
2. user specifies 'prefer' policy, but with empty nodemask
3. system 'default' policy is used
4. 'prefer' policy + valid 'preferred' node with MPOL_F_STATIC_NODES
flag set, and when it is 'rebind' to a nodemask which doesn't contains
the 'preferred' node, it will perform as 'local' policy
So make 'local' a real policy instead of a fake 'prefer' one, and kill
MPOL_F_LOCAL bit, which can greatly reduce the confusion for code reading.
For case 4, the logic of mpol_rebind_preferred() is confusing, as Michal
Hocko pointed out:
: I do believe that rebinding preferred policy is just bogus and it should
: be dropped altogether on the ground that a preference is a mere hint from
: userspace where to start the allocation. Unless I am missing something
: cpusets will be always authoritative for the final placement. The
: preferred node just acts as a starting point and it should be really
: preserved when cpusets changes. Otherwise we have a very subtle behavior
: corner cases.
So dump all the tricky transformation between 'prefer' and 'local', and
just record the new nodemask of rebinding.
[[email protected]: fix a problem in mpol_set_nodemask(), per Michal Hocko]
Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: refine code and comments of mpol_set_nodemask(), per Michal]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Feng Tang <[email protected]>
Suggested-by: Michal Hocko <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Ben Widawsky <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Patch series "mm/mempolicy: some fix and semantics cleanup", v4.
Current memory policy code has some confusing and ambiguous part about
MPOL_LOCAL policy, as it is handled as a faked MPOL_PREFERRED one, and
there are many places having to distinguish them. Also the nodemask
intersection check needs cleanup to be more explicit for OOM use, and
handle MPOL_INTERLEAVE correctly. This patchset cleans up these and
unifies the parameter sanity check for mbind() and set_mempolicy().
This patch (of 3):
mempolicy_nodemask_intersects seem to be a general purpose mempolicy
function. In fact it is partially tailored for the OOM purpose
instead. The oom proper is the only existing user so rename the
function to make that purpose explicit.
While at it drop the MPOL_INTERLEAVE as those allocations never has a
nodemask defined (see alloc_page_interleave) so this is a dead code and
a confusing one because MPOL_INTERLEAVE is a hint rather than a hard
requirement so it shouldn't be considered during the OOM.
The final code can be reduced to a check for MPOL_BIND which is the
only memory policy that is a hard requirement and thus relevant to a
constrained OOM logic.
[[email protected]: changelog edits]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Feng Tang <[email protected]>
Suggested-by: Michal Hocko <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Ben Widawsky <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Patch series "Cleanups for zbud", v2.
This series contains just cleanups to save some possible memory in
zbud_pool and avoid exporting any unneeded zbud API. More details can be
found in the respective changelogs
This patch (of 2):
Since commit 9d8c5b5284 ("mm: zbud: fix condition check on allocation
size"), zbud_pool.unbuddied[0] is always unused. We can reuse it as
buddied field to save some possible memory.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Dan Streetman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
handle_to_z3fold_header() is unused now. So we can remove it. As a
result, get_z3fold_header() becomes the only caller of
__get_z3fold_header() and the argument lock is always true. Therefore we
could further fold the __get_z3fold_header() into get_z3fold_header() with
lock = true.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Vitaly Wool <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
It's meaningless to pass a magic number 2 to __alloc_percpu() as there is
a minimum alignment size of PCPU_MIN_ALLOC_SIZE (> 2) in it. Also there
is no special alignment requirement for unbuddied. So we could replace
this magic number with nature alignment, i.e. __alignof__(struct
list_head), to improve readability.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Vitaly Wool <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
It is not enough to just make sure the z3fold header is not larger than
the page size. When z3fold header is equal to PAGE_SIZE, we would
underflow when check alloc size against PAGE_SIZE - ZHDR_SIZE_ALIGNED -
CHUNK_SIZE in z3fold_alloc(). Make sure there has remaining spaces for
its buddy to fix this theoretical issue.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Vitaly Wool <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Patch series "Cleanup and fixup for z3fold".
This series contains cleanups to remove unused function, redefine macro to
improve readability and so on. Also this fixes several bugs in z3fold,
such as memory leak in z3fold_destroy_pool(). More details can be found
in the respective changelogs.
This patch (of 6):
To improve code readability, we could define macro NCHUNKS as TOTAL_CHUNKS
- ZHDR_CHUNKS. No functional change intended.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Vitaly Wool <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Let's properly use page_offline_(start|end) to synchronize setting
PageOffline(), so we won't have valid page access to unplugged memory
regions from /proc/kcore.
Existing balloon implementations usually allow reading inflated memory;
doing so might result in unnecessary overhead in the hypervisor, which is
currently the case with virtio-mem.
For future virtio-mem use cases, it will be different when using shmem,
huge pages, !anonymous private mappings, ... as backing storage for a VM.
virtio-mem unplugged memory must no longer be accessed and access might
result in undefined behavior. There will be a virtio spec extension to
document this change, including a new feature flag indicating the changed
behavior. We really don't want to race against PFN walkers reading random
page content.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Acked-by: Mike Rapoport <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: Aili Yao <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Wei Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
A driver might set a page logically offline -- PageOffline() -- and turn
the page inaccessible in the hypervisor; after that, access to page
content can be fatal. One example is virtio-mem; while unplugged memory
-- marked as PageOffline() can currently be read in the hypervisor, this
will no longer be the case in the future; for example, when having a
virtio-mem device backed by huge pages in the hypervisor.
Some special PFN walkers -- i.e., /proc/kcore -- read content of random
pages after checking PageOffline(); however, these PFN walkers can race
with drivers that set PageOffline().
Let's introduce page_offline_(begin|end|freeze|thaw) for synchronizing.
page_offline_freeze()/page_offline_thaw() allows for a subsystem to
synchronize with such drivers, achieving that a page cannot be set
PageOffline() while frozen.
page_offline_begin()/page_offline_end() is used by drivers that care about
such races when setting a page PageOffline().
For simplicity, use a rwsem for now; neither drivers nor users are
performance sensitive.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: Aili Yao <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Wei Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Let's avoid reading:
1) Offline memory sections: the content of offline memory sections is
stale as the memory is effectively unused by the kernel. On s390x with
standby memory, offline memory sections (belonging to offline storage
increments) are not accessible. With virtio-mem and the hyper-v
balloon, we can have unavailable memory chunks that should not be
accessed inside offline memory sections. Last but not least, offline
memory sections might contain hwpoisoned pages which we can no longer
identify because the memmap is stale.
2) PG_offline pages: logically offline pages that are documented as
"The content of these pages is effectively stale. Such pages should
not be touched (read/write/dump/save) except by their owner.".
Examples include pages inflated in a balloon or unavailble memory
ranges inside hotplugged memory sections with virtio-mem or the hyper-v
balloon.
3) PG_hwpoison pages: Reading pages marked as hwpoisoned can be fatal.
As documented: "Accessing is not safe since it may cause another
machine check. Don't touch!"
Introduce is_page_hwpoison(), adding a comment that it is inherently racy
but best we can really do.
Reading /proc/kcore now performs similar checks as when reading
/proc/vmcore for kdump via makedumpfile: problematic pages are exclude.
It's also similar to hibernation code, however, we don't skip hwpoisoned
pages when processing pages in kernel/power/snapshot.c:saveable_page()
yet.
Note 1: we can race against memory offlining code, especially memory going
offline and getting unplugged: however, we will properly tear down the
identity mapping and handle faults gracefully when accessing this memory
from kcore code.
Note 2: we can race against drivers setting PageOffline() and turning
memory inaccessible in the hypervisor. We'll handle this in a follow-up
patch.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: Aili Yao <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Wei Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Patch series "fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages", v3.
Looking for places where the kernel might unconditionally read
PageOffline() pages, I stumbled over /proc/kcore; turns out /proc/kcore
needs some more love to not touch some other pages we really don't want to
read -- i.e., hwpoisoned ones.
Examples for PageOffline() pages are pages inflated in a balloon, memory
unplugged via virtio-mem, and partially-present sections in memory added
by the Hyper-V balloon.
When reading pages inflated in a balloon, we essentially produce
unnecessary load in the hypervisor; holes in partially present sections in
case of Hyper-V are not accessible and already were a problem for
/proc/vmcore, fixed in makedumpfile by detecting PageOffline() pages. In
the future, virtio-mem might disallow reading unplugged memory -- marked
as PageOffline() -- in some environments, resulting in undefined behavior
when accessed; therefore, I'm trying to identify and rework all these
(corner) cases.
With this series, there is really only access via /dev/mem, /proc/vmcore
and kdb left after I ripped out /dev/kmem. kdb is an advanced corner-case
use case -- we won't care for now if someone explicitly tries to do nasty
things by reading from/writing to physical addresses we better not touch.
/dev/mem is a use case we won't support for virtio-mem, at least for now,
so we'll simply disallow mapping any virtio-mem memory via /dev/mem next.
/proc/vmcore is really only a problem when dumping the old kernel via
something that's not makedumpfile (read: basically never), however, we'll
try sanitizing that as well in the second kernel in the future.
Tested via kcore_dump:
https://github.com/schlafwandler/kcore_dump
This patch (of 6):
Commit db779ef67f ("proc/kcore: Remove unused kclist_add_remap()")
removed the last user of KCORE_REMAP.
Commit 595dd46ebf ("vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when
dumping vsyscall user page") removed the last user of KCORE_OTHER.
Let's drop both types. While at it, also drop vaddr in "struct
kcore_list", used by KCORE_REMAP only.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Aili Yao <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Wei Liu <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Theoretically without the protect from memalloc_noreclaim_save() and
memalloc_noreclaim_restore(), reclaim_pages() can go into the block
I/O layer recursively and deadlock.
Querying 'reclaim_pages' in our kernel crash databases didn't yield
any results. So the deadlock seems unlikely to happen. A possible
explanation is that the only user of reclaim_pages(), i.e.,
MADV_PAGEOUT, is usually called before memory pressure builds up,
e.g., on Android and Chrome OS. Under such a condition, allocations in
the block I/O layer can be fulfilled without diverting to direct
reclaim and therefore the recursion is avoided.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yu Zhao <[email protected]>
Cc: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Kefeng Wang