linux/include/asm-generic/pgtable.h, branch v4.0

mm: remove remaining references to NUMA hinting bits and helpers

2015-02-13T02:54:08Z

This patch removes the NUMA PTE bits and associated helpers. As a side-effect it increases the maximum possible swap space on x86-64. One potential source of problems is races between the marking of PTEs PROT_NONE, NUMA hinting faults and migration. It must be guaranteed that a PTE being protected is not faulted in parallel, seen as a pte_none and corrupting memory. The base case is safe but transhuge has problems in the past due to an different migration mechanism and a dependance on page lock to serialise migrations and warrants a closer look. task_work hinting update parallel fault ------------------------ -------------- change_pmd_range change_huge_pmd __pmd_trans_huge_lock pmdp_get_and_clear __handle_mm_fault pmd_none do_huge_pmd_anonymous_page read? pmd_lock blocks until hinting complete, fail !pmd_none test write? __do_huge_pmd_anonymous_page acquires pmd_lock, checks pmd_none pmd_modify set_pmd_at task_work hinting update parallel migration ------------------------ ------------------ change_pmd_range change_huge_pmd __pmd_trans_huge_lock pmdp_get_and_clear __handle_mm_fault do_huge_pmd_numa_page migrate_misplaced_transhuge_page pmd_lock waits for updates to complete, recheck pmd_same pmd_modify set_pmd_at Both of those are safe and the case where a transhuge page is inserted during a protection update is unchanged. The case where two processes try migrating at the same time is unchanged by this series so should still be ok. I could not find a case where we are accidentally depending on the PTE not being cleared and flushed. If one is missed, it'll manifest as corruption problems that start triggering shortly after this series is merged and only happen when NUMA balancing is enabled. Signed-off-by: Mel Gorman Tested-by: Sasha Levin Cc: Aneesh Kumar K.V Cc: Benjamin Herrenschmidt Cc: Dave Jones Cc: Hugh Dickins Cc: Ingo Molnar Cc: Kirill Shutemov Cc: Linus Torvalds Cc: Paul Mackerras Cc: Rik van Riel Cc: Mark Brown Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: add p[te|md] protnone helpers for use by NUMA balancing

2015-02-13T02:54:08Z

This is a preparatory patch that introduces protnone helpers for automatic NUMA balancing. Signed-off-by: Mel Gorman Acked-by: Linus Torvalds Acked-by: Aneesh Kumar K.V Tested-by: Sasha Levin Cc: Benjamin Herrenschmidt Cc: Dave Jones Cc: Hugh Dickins Cc: Ingo Molnar Cc: Kirill Shutemov Cc: Paul Mackerras Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

asm-generic: drop unused pte_file* helpers

2015-02-10T22:30:31Z

All users are gone. Signed-off-by: Kirill A. Shutemov Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

s390/mm: pmdp_get_and_clear_full optimization

2014-10-27T12:27:30Z

Analog to ptep_get_and_clear_full define a variant of the pmpd_get_and_clear primitive which gets the full hint from the mmu_gather struct. This allows s390 to avoid a costly instruction when destroying an address space. Signed-off-by: Martin Schwidefsky

mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared

2014-10-14T00:18:28Z

For VMAs that don't want write notifications, PTEs created for read faults have their write bit set. If the read fault happens after VM_SOFTDIRTY is cleared, then the PTE's softdirty bit will remain clear after subsequent writes. Here's a simple code snippet to demonstrate the bug: char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0); system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */ assert(*m == '\0'); /* new PTE allows write access */ assert(!soft_dirty(x)); *m = 'x'; /* should dirty the page */ assert(soft_dirty(x)); /* fails */ With this patch, write notifications are enabled when VM_SOFTDIRTY is cleared. Furthermore, to avoid unnecessary faults, write notifications are disabled when VM_SOFTDIRTY is set. As a side effect of enabling and disabling write notifications with care, this patch fixes a bug in mprotect where vm_page_prot bits set by drivers were zapped on mprotect. An analogous bug was fixed in mmap by commit c9d0bf241451 ("mm: uncached vma support with writenotify"). Signed-off-by: Peter Feiner Reported-by: Peter Feiner Suggested-by: Kirill A. Shutemov Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Cc: Jamie Liu Cc: Hugh Dickins Cc: Naoya Horiguchi Cc: Bjorn Helgaas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'akpm' (fixes from Andrew Morton)

2014-10-10T02:26:14Z

Merge patch-bomb from Andrew Morton: - part of OCFS2 (review is laggy again) - procfs - slab - all of MM - zram, zbud - various other random things: arch, filesystems. * emailed patches from Andrew Morton : (164 commits) nosave: consolidate __nosave_{begin,end} in include/linux/screen_info.h: remove unused ORIG_* macros kernel/sys.c: compat sysinfo syscall: fix undefined behavior kernel/sys.c: whitespace fixes acct: eliminate compile warning kernel/async.c: switch to pr_foo() include/linux/blkdev.h: use NULL instead of zero include/linux/kernel.h: deduplicate code implementing clamp* macros include/linux/kernel.h: rewrite min3, max3 and clamp using min and max alpha: use Kbuild logic to include frv: remove deprecated IRQF_DISABLED frv: remove unused cpuinfo_frv and friends to fix future build error zbud: avoid accessing last unused freelist zsmalloc: simplify init_zspage free obj linking mm/zsmalloc.c: correct comment for fullness group computation zram: use notify_free to account all free notifications zram: report maximum used memory zram: zram memory size limitation zsmalloc: change return value unit of zs_get_total_size_bytes zsmalloc: move pages_allocated to zs_pool ...

mm: remove misleading ARCH_USES_NUMA_PROT_NONE

2014-10-10T02:25:52Z

ARCH_USES_NUMA_PROT_NONE was defined for architectures that implemented _PAGE_NUMA using _PROT_NONE. This saved using an additional PTE bit and relied on the fact that PROT_NONE vmas were skipped by the NUMA hinting fault scanner. This was found to be conceptually confusing with a lot of implicit assumptions and it was asked that an alternative be found. Commit c46a7c81 "x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels" redefined _PAGE_NUMA on x86 to be one of the swap PTE bits and shrunk the maximum possible swap size but it did not go far enough. There are no architectures that reuse _PROT_NONE as _PROT_NUMA but the relics still exist. This patch removes ARCH_USES_NUMA_PROT_NONE and removes some unnecessary duplication in powerpc vs the generic implementation by defining the types the core NUMA helpers expected to exist from x86 with their ppc64 equivalent. This necessitated that a PTE bit mask be created that identified the bits that distinguish present from NUMA pte entries but it is expected this will only differ between arches based on _PAGE_PROTNONE. The naming for the generic helpers was taken from x86 originally but ppc64 has types that are equivalent for the purposes of the helper so they are mapped instead of duplicating code. Signed-off-by: Mel Gorman Cc: Hugh Dickins Cc: "Kirill A. Shutemov" Cc: Rik van Riel Cc: Johannes Weiner Cc: Cyrill Gorcunov Reviewed-by: Aneesh Kumar K.V Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

PCI: Add pci_remap_iospace() to map bus I/O resources

2014-09-30T23:08:57Z

Add pci_remap_iospace() to map bus I/O resources into the CPU virtual address space. Architectures with special needs may provide their own version, but most should be able to use this one. This function is useful for PCI host bridge drivers that need to map the PCI I/O resources into virtual memory space. [bhelgaas: phys_addr description, drop temporary "err" variable] Signed-off-by: Liviu Dudau Signed-off-by: Bjorn Helgaas Reviewed-by: Rob Herring Reviewed-by: Catalin Marinas CC: Arnd Bergmann

x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels

2014-06-04T23:53:55Z

_PAGE_NUMA is currently an alias of _PROT_PROTNONE to trap NUMA hinting faults on x86. Care is taken such that _PAGE_NUMA is used only in situations where the VMA flags distinguish between NUMA hinting faults and prot_none faults. This decision was x86-specific and conceptually it is difficult requiring special casing to distinguish between PROTNONE and NUMA ptes based on context. Fundamentally, we only need the _PAGE_NUMA bit to tell the difference between an entry that is really unmapped and a page that is protected for NUMA hinting faults as if the PTE is not present then a fault will be trapped. Swap PTEs on x86-64 use the bits after _PAGE_GLOBAL for the offset. This patch shrinks the maximum possible swap size and uses the bit to uniquely distinguish between NUMA hinting ptes and swap ptes. Signed-off-by: Mel Gorman Cc: David Vrabel Cc: Ingo Molnar Cc: Peter Anvin Cc: Fengguang Wu Cc: Linus Torvalds Cc: Steven Noonan Cc: Rik van Riel Cc: Peter Zijlstra Cc: Andrea Arcangeli Cc: Dave Hansen Cc: Srikar Dronamraju Cc: Cyrill Gorcunov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: use paravirt friendly ops for NUMA hinting ptes

2014-04-18T23:40:09Z

David Vrabel identified a regression when using automatic NUMA balancing under Xen whereby page table entries were getting corrupted due to the use of native PTE operations. Quoting him Xen PV guest page tables require that their entries use machine addresses if the preset bit (_PAGE_PRESENT) is set, and (for successful migration) non-present PTEs must use pseudo-physical addresses. This is because on migration MFNs in present PTEs are translated to PFNs (canonicalised) so they may be translated back to the new MFN in the destination domain (uncanonicalised). pte_mknonnuma(), pmd_mknonnuma(), pte_mknuma() and pmd_mknuma() set and clear the _PAGE_PRESENT bit using pte_set_flags(), pte_clear_flags(), etc. In a Xen PV guest, these functions must translate MFNs to PFNs when clearing _PAGE_PRESENT and translate PFNs to MFNs when setting _PAGE_PRESENT. His suggested fix converted p[te|md]_[set|clear]_flags to using paravirt-friendly ops but this is overkill. He suggested an alternative of using p[te|md]_modify in the NUMA page table operations but this is does more work than necessary and would require looking up a VMA for protections. This patch modifies the NUMA page table operations to use paravirt friendly operations to set/clear the flags of interest. Unfortunately this will take a performance hit when updating the PTEs on CONFIG_PARAVIRT but I do not see a way around it that does not break Xen. Signed-off-by: Mel Gorman Acked-by: David Vrabel Tested-by: David Vrabel Cc: Ingo Molnar Cc: Peter Anvin Cc: Fengguang Wu Cc: Linus Torvalds Cc: Steven Noonan Cc: Rik van Riel Cc: Peter Zijlstra Cc: Andrea Arcangeli Cc: Dave Hansen Cc: Srikar Dronamraju Cc: Cyrill Gorcunov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds