kernel.git/mm/ksm.c, branch linux-4.18.y

mm/ksm.c: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm()

2018-06-14T22:55:23Z

In our armv8a server(QDF2400), I noticed lots of WARN_ON caused by PAGE_SIZE unaligned for rmap_item->address under memory pressure tests(start 20 guests and run memhog in the host). WARNING: CPU: 4 PID: 4641 at virt/kvm/arm/mmu.c:1826 kvm_age_hva_handler+0xc0/0xc8 CPU: 4 PID: 4641 Comm: memhog Tainted: G W 4.17.0-rc3+ #8 Call trace: kvm_age_hva_handler+0xc0/0xc8 handle_hva_to_gpa+0xa8/0xe0 kvm_age_hva+0x4c/0xe8 kvm_mmu_notifier_clear_flush_young+0x54/0x98 __mmu_notifier_clear_flush_young+0x6c/0xa0 page_referenced_one+0x154/0x1d8 rmap_walk_ksm+0x12c/0x1d0 rmap_walk+0x94/0xa0 page_referenced+0x194/0x1b0 shrink_page_list+0x674/0xc28 shrink_inactive_list+0x26c/0x5b8 shrink_node_memcg+0x35c/0x620 shrink_node+0x100/0x430 do_try_to_free_pages+0xe0/0x3a8 try_to_free_pages+0xe4/0x230 __alloc_pages_nodemask+0x564/0xdc0 alloc_pages_vma+0x90/0x228 do_anonymous_page+0xc8/0x4d0 __handle_mm_fault+0x4a0/0x508 handle_mm_fault+0xf8/0x1b0 do_page_fault+0x218/0x4b8 do_translation_fault+0x90/0xa0 do_mem_abort+0x68/0xf0 el0_da+0x24/0x28 In rmap_walk_ksm, the rmap_item->address might still have the STABLE_FLAG, then the start and end in handle_hva_to_gpa might not be PAGE_SIZE aligned. Thus it will cause exceptions in handle_hva_to_gpa on arm64. This patch fixes it by ignoring (not removing) the low bits of address when doing rmap_walk_ksm. IMO, it should be backported to stable tree. the storm of WARN_ONs is very easy for me to reproduce. More than that, I watched a panic (not reproducible) as follows: page:ffff7fe003742d80 count:-4871 mapcount:-2126053375 mapping: (null) index:0x0 flags: 0x1fffc00000000000() raw: 1fffc00000000000 0000000000000000 0000000000000000 ffffecf981470000 raw: dead000000000100 dead000000000200 ffff8017c001c000 0000000000000000 page dumped because: nonzero _refcount CPU: 29 PID: 18323 Comm: qemu-kvm Tainted: G W 4.14.15-5.hxt.aarch64 #1 Hardware name: Call trace: dump_backtrace+0x0/0x22c show_stack+0x24/0x2c dump_stack+0x8c/0xb0 bad_page+0xf4/0x154 free_pages_check_bad+0x90/0x9c free_pcppages_bulk+0x464/0x518 free_hot_cold_page+0x22c/0x300 __put_page+0x54/0x60 unmap_stage2_range+0x170/0x2b4 kvm_unmap_hva_handler+0x30/0x40 handle_hva_to_gpa+0xb0/0xec kvm_unmap_hva_range+0x5c/0xd0 I even injected a fault on purpose in kvm_unmap_hva_range by seting size=size-0x200, the call trace is similar as above. So I thought the panic is similarly caused by the root cause of WARN_ON. Andrea said: : It looks a straightforward safe fix, on x86 hva_to_gfn_memslot would : zap those bits and hide the misalignment caused by the low metadata : bits being erroneously left set in the address, but the arm code : notices when that's the last page in the memslot and the hva_end is : getting aligned and the size is below one page. : : I think the problem triggers in the addr += PAGE_SIZE of : unmap_stage2_ptes that never matches end because end is aligned but : addr is not. : : } while (pte++, addr += PAGE_SIZE, addr != end); : : x86 again only works on hva_start/hva_end after converting it to : gfn_start/end and that being in pfn units the bits are zapped before : they risk to cause trouble. Jia He said: : I've tested by myself in arm64 server (QDF2400,46 cpus,96G mem) Without : this patch, the WARN_ON is very easy for reproducing. After this patch, I : have run the same benchmarch for a whole day without any WARN_ONs Link: http://lkml.kernel.org/r/1525403506-6750-1-git-send-email-hejianet@gmail.com Signed-off-by: Jia He Reviewed-by: Andrea Arcangeli Tested-by: Jia He Cc: Suzuki K Poulose Cc: Minchan Kim Cc: Claudio Imbrenda Cc: Arvind Yadav Cc: Mike Rapoport Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/ksm: move [set_]page_stable_node from ksm.h to ksm.c

2018-06-08T00:34:36Z

page_stable_node() and set_page_stable_node() are only used in mm/ksm.c and there is no point to keep them in the include/linux/ksm.h [akpm@linux-foundation.org: fix SYSFS=n build] Link: http://lkml.kernel.org/r/1524552106-7356-3-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport Reviewed-by: Andrew Morton Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/ksm: docs: extend overview comment and make it "DOC:"

2018-04-27T23:19:24Z

The existing comment provides a good overview of KSM implementation. Let's update it to reflect recent additions of "chain" and "dup" variants of the stable tree nodes and mark it as "DOC:" for inclusion into the KSM documentation. Signed-off-by: Mike Rapoport Signed-off-by: Jonathan Corbet

Merge branch 'mm-rst' into docs-next

2018-04-16T20:25:08Z

Mike Rapoport says: These patches convert files in Documentation/vm to ReST format, add an initial index and link it to the top level documentation. There are no contents changes in the documentation, except few spelling fixes. The relatively large diffstat stems from the indentation and paragraph wrapping changes. I've tried to keep the formatting as consistent as possible, but I could miss some places that needed markup and add some markup where it was not necessary. [jc: significant conflicts in vm/hmm.rst]

docs/vm: rename documentation files to .rst

2018-04-16T20:18:15Z

Signed-off-by: Mike Rapoport Signed-off-by: Jonathan Corbet

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

2018-04-11T17:28:31Z

When using KSM with use_zero_pages, we replace anonymous pages containing only zeroes with actual zero pages, which are not anonymous. We need to do proper accounting of the mm counters, otherwise we will get wrong values in /proc and a BUG message in dmesg when tearing down the mm. Link: http://lkml.kernel.org/r/1522931274-15552-1-git-send-email-imbrenda@linux.vnet.ibm.com Fixes: e86c59b1b1 ("mm/ksm: improve deduplication of zero pages with colouring") Signed-off-by: Claudio Imbrenda Reviewed-by: Andrew Morton Cc: Andrea Arcangeli Cc: Minchan Kim Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Christian Borntraeger Cc: Gerald Schaefer Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/ksm: fix interaction with THP

2018-04-06T04:36:27Z

This patch fixes a corner case for KSM. When two pages belong or belonged to the same transparent hugepage, and they should be merged, KSM fails to split the page, and therefore no merging happens. This bug can be reproduced by: * making sure ksm is running (in case disabling ksmtuned) * enabling transparent hugepages * allocating a THP-aligned 1-THP-sized buffer e.g. on amd64: posix_memalign(&p, 1<<21, 1<<21) * filling it with the same values e.g. memset(p, 42, 1<<21) * performing madvise to make it mergeable e.g. madvise(p, 1<<21, MADV_MERGEABLE) * waiting for KSM to perform a few scans The expected outcome is that the all the pages get merged (1 shared and the rest sharing); the actual outcome is that no pages get merged (1 unshared and the rest volatile) The reason of this behaviour is that we increase the reference count once for both pages we want to merge, but if they belong to the same hugepage (or compound page), the reference counter used in both cases is the one of the head of the compound page. This means that split_huge_page will find a value of the reference counter too high and will fail. This patch solves this problem by testing if the two pages to merge belong to the same hugepage when attempting to merge them. If so, the hugepage is split safely. This means that the hugepage is not split if not necessary. Link: http://lkml.kernel.org/r/1521548069-24758-1-git-send-email-imbrenda@linux.vnet.ibm.com Signed-off-by: Claudio Imbrenda Co-authored-by: Gerald Schaefer Reviewed-by: Andrew Morton Cc: Andrea Arcangeli Cc: Minchan Kim Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Christian Borntraeger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/ksm.c: make stable_node_dup() static

2018-04-06T04:36:24Z

stable_node_dup() is local to the source and does not need to be in global scope, so make it static. Cleans up sparse warning: mm/ksm.c:1321:13: warning: symbol 'stable_node_dup' was not declared. Should it be static? Link: http://lkml.kernel.org/r/20180206221005.12642-1-colin.king@canonical.com Signed-off-by: Colin Ian King Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sparc64: Add support for ADI (Application Data Integrity)

2018-03-18T14:38:48Z

ADI is a new feature supported on SPARC M7 and newer processors to allow hardware to catch rogue accesses to memory. ADI is supported for data fetches only and not instruction fetches. An app can enable ADI on its data pages, set version tags on them and use versioned addresses to access the data pages. Upper bits of the address contain the version tag. On M7 processors, upper four bits (bits 63-60) contain the version tag. If a rogue app attempts to access ADI enabled data pages, its access is blocked and processor generates an exception. Please see Documentation/sparc/adi.txt for further details. This patch extends mprotect to enable ADI (TSTATE.mcde), enable/disable MCD (Memory Corruption Detection) on selected memory ranges, enable TTE.mcd in PTEs, return ADI parameters to userspace and save/restore ADI version tags on page swap out/in or migration. ADI is not enabled by default for any task. A task must explicitly enable ADI on a memory range and set version tag for ADI to be effective for the task. Signed-off-by: Khalid Aziz Cc: Khalid Aziz Reviewed-by: Anthony Yznaga Signed-off-by: David S. Miller

mm: docs: fixup punctuation

2018-02-07T02:32:48Z

so that kernel-doc will properly recognize the parameter and function descriptions. Link: http://lkml.kernel.org/r/1516700871-22279-2-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds