forked from luck/tmp_suning_uos_patched
Revert "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"
This reverts commit2947ba054a. Dan Williams reported dax-pmem kernel warnings with the following signature: WARNING: CPU: 8 PID: 245 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1f5/0x200 percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic ... and bisected it to this commit, which suggests possible memory corruption caused by the x86 fast-GUP conversion. He also pointed out: " This is similar to the backtrace when we were not properly handling pud faults and was fixed with this commit:220ced1676"mm: fix get_user_pages() vs device-dax pud mappings" I've found some missing _devmap checks in the generic get_user_pages_fast() path, but this does not fix the regression [...] " So given that there are known bugs, and a pretty robust looking bisection points to this commit suggesting that are unknown bugs in the conversion as well, revert it for the time being - we'll re-try in v4.13. Reported-by: Dan Williams <dan.j.williams@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: aneesh.kumar@linux.vnet.ibm.com Cc: dann.frazier@canonical.com Cc: dave.hansen@intel.com Cc: steve.capper@linaro.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
parent
ace2fb5a8b
commit
6dd29b3df9
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@ -1666,7 +1666,7 @@ config ARCH_SELECT_MEMORY_MODEL
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config HAVE_ARCH_PFN_VALID
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def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
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config HAVE_GENERIC_GUP
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config HAVE_GENERIC_RCU_GUP
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def_bool y
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depends on ARM_LPAE
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@ -205,7 +205,7 @@ config GENERIC_CALIBRATE_DELAY
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config ZONE_DMA
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def_bool y
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config HAVE_GENERIC_GUP
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config HAVE_GENERIC_RCU_GUP
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def_bool y
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config ARCH_DMA_ADDR_T_64BIT
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@ -135,7 +135,7 @@ config PPC
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select HAVE_FUNCTION_GRAPH_TRACER
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select HAVE_FUNCTION_TRACER
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select HAVE_GCC_PLUGINS
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select HAVE_GENERIC_GUP
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select HAVE_GENERIC_RCU_GUP
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select HAVE_HW_BREAKPOINT if PERF_EVENTS && (PPC_BOOK3S || PPC_8xx)
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select HAVE_IDE
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select HAVE_IOREMAP_PROT
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@ -2789,9 +2789,6 @@ config X86_DMA_REMAP
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bool
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depends on STA2X11
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config HAVE_GENERIC_GUP
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def_bool y
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source "net/Kconfig"
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source "drivers/Kconfig"
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@ -220,6 +220,18 @@ static inline int vma_pkey(struct vm_area_struct *vma)
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}
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#endif
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static inline bool __pkru_allows_pkey(u16 pkey, bool write)
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{
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u32 pkru = read_pkru();
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if (!__pkru_allows_read(pkru, pkey))
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return false;
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if (write && !__pkru_allows_write(pkru, pkey))
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return false;
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return true;
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}
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/*
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* We only want to enforce protection keys on the current process
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* because we effectively have no access to PKRU for other
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@ -212,51 +212,4 @@ static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
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#define __pte_to_swp_entry(pte) ((swp_entry_t){ (pte).pte_high })
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#define __swp_entry_to_pte(x) ((pte_t){ { .pte_high = (x).val } })
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#define gup_get_pte gup_get_pte
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/*
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* WARNING: only to be used in the get_user_pages_fast() implementation.
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*
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* With get_user_pages_fast(), we walk down the pagetables without taking
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* any locks. For this we would like to load the pointers atomically,
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* but that is not possible (without expensive cmpxchg8b) on PAE. What
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* we do have is the guarantee that a PTE will only either go from not
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* present to present, or present to not present or both -- it will not
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* switch to a completely different present page without a TLB flush in
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* between; something that we are blocking by holding interrupts off.
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*
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* Setting ptes from not present to present goes:
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*
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* ptep->pte_high = h;
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* smp_wmb();
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* ptep->pte_low = l;
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*
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* And present to not present goes:
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*
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* ptep->pte_low = 0;
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* smp_wmb();
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* ptep->pte_high = 0;
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*
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* We must ensure here that the load of pte_low sees 'l' iff pte_high
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* sees 'h'. We load pte_high *after* loading pte_low, which ensures we
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* don't see an older value of pte_high. *Then* we recheck pte_low,
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* which ensures that we haven't picked up a changed pte high. We might
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* have gotten rubbish values from pte_low and pte_high, but we are
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* guaranteed that pte_low will not have the present bit set *unless*
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* it is 'l'. Because get_user_pages_fast() only operates on present ptes
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* we're safe.
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*/
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static inline pte_t gup_get_pte(pte_t *ptep)
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{
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pte_t pte;
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do {
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pte.pte_low = ptep->pte_low;
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smp_rmb();
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pte.pte_high = ptep->pte_high;
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smp_rmb();
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} while (unlikely(pte.pte_low != ptep->pte_low));
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return pte;
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}
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#endif /* _ASM_X86_PGTABLE_3LEVEL_H */
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@ -244,11 +244,6 @@ static inline int pud_devmap(pud_t pud)
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return 0;
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}
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#endif
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static inline int pgd_devmap(pgd_t pgd)
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{
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return 0;
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}
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#endif
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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@ -1190,54 +1185,6 @@ static inline u16 pte_flags_pkey(unsigned long pte_flags)
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#endif
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}
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static inline bool __pkru_allows_pkey(u16 pkey, bool write)
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{
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u32 pkru = read_pkru();
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if (!__pkru_allows_read(pkru, pkey))
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return false;
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if (write && !__pkru_allows_write(pkru, pkey))
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return false;
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return true;
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}
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/*
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* 'pteval' can come from a PTE, PMD or PUD. We only check
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* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
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* same value on all 3 types.
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*/
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static inline bool __pte_access_permitted(unsigned long pteval, bool write)
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{
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unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
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if (write)
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need_pte_bits |= _PAGE_RW;
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if ((pteval & need_pte_bits) != need_pte_bits)
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return 0;
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return __pkru_allows_pkey(pte_flags_pkey(pteval), write);
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}
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#define pte_access_permitted pte_access_permitted
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static inline bool pte_access_permitted(pte_t pte, bool write)
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{
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return __pte_access_permitted(pte_val(pte), write);
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}
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#define pmd_access_permitted pmd_access_permitted
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static inline bool pmd_access_permitted(pmd_t pmd, bool write)
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{
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return __pte_access_permitted(pmd_val(pmd), write);
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}
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#define pud_access_permitted pud_access_permitted
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static inline bool pud_access_permitted(pud_t pud, bool write)
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{
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return __pte_access_permitted(pud_val(pud), write);
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}
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#include <asm-generic/pgtable.h>
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#endif /* __ASSEMBLY__ */
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@ -227,20 +227,6 @@ extern void cleanup_highmap(void);
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extern void init_extra_mapping_uc(unsigned long phys, unsigned long size);
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extern void init_extra_mapping_wb(unsigned long phys, unsigned long size);
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#define gup_fast_permitted gup_fast_permitted
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static inline bool gup_fast_permitted(unsigned long start, int nr_pages,
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int write)
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{
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unsigned long len, end;
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len = (unsigned long)nr_pages << PAGE_SHIFT;
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end = start + len;
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if (end < start)
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return false;
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if (end >> __VIRTUAL_MASK_SHIFT)
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return false;
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return true;
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}
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#endif /* !__ASSEMBLY__ */
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#endif /* _ASM_X86_PGTABLE_64_H */
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@ -2,7 +2,7 @@
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KCOV_INSTRUMENT_tlb.o := n
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obj-y := init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
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pat.o pgtable.o physaddr.o setup_nx.o tlb.o
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pat.o pgtable.o physaddr.o gup.o setup_nx.o tlb.o
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# Make sure __phys_addr has no stackprotector
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nostackp := $(call cc-option, -fno-stack-protector)
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496
arch/x86/mm/gup.c
Normal file
496
arch/x86/mm/gup.c
Normal file
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@ -0,0 +1,496 @@
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/*
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* Lockless get_user_pages_fast for x86
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*
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* Copyright (C) 2008 Nick Piggin
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* Copyright (C) 2008 Novell Inc.
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*/
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/vmstat.h>
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#include <linux/highmem.h>
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#include <linux/swap.h>
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#include <linux/memremap.h>
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#include <asm/mmu_context.h>
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#include <asm/pgtable.h>
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static inline pte_t gup_get_pte(pte_t *ptep)
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{
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#ifndef CONFIG_X86_PAE
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return READ_ONCE(*ptep);
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#else
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/*
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* With get_user_pages_fast, we walk down the pagetables without taking
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* any locks. For this we would like to load the pointers atomically,
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* but that is not possible (without expensive cmpxchg8b) on PAE. What
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* we do have is the guarantee that a pte will only either go from not
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* present to present, or present to not present or both -- it will not
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* switch to a completely different present page without a TLB flush in
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* between; something that we are blocking by holding interrupts off.
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*
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* Setting ptes from not present to present goes:
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* ptep->pte_high = h;
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* smp_wmb();
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* ptep->pte_low = l;
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*
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* And present to not present goes:
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* ptep->pte_low = 0;
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* smp_wmb();
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* ptep->pte_high = 0;
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*
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* We must ensure here that the load of pte_low sees l iff pte_high
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* sees h. We load pte_high *after* loading pte_low, which ensures we
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* don't see an older value of pte_high. *Then* we recheck pte_low,
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* which ensures that we haven't picked up a changed pte high. We might
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* have got rubbish values from pte_low and pte_high, but we are
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* guaranteed that pte_low will not have the present bit set *unless*
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* it is 'l'. And get_user_pages_fast only operates on present ptes, so
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* we're safe.
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*
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* gup_get_pte should not be used or copied outside gup.c without being
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* very careful -- it does not atomically load the pte or anything that
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* is likely to be useful for you.
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*/
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pte_t pte;
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retry:
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pte.pte_low = ptep->pte_low;
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smp_rmb();
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pte.pte_high = ptep->pte_high;
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smp_rmb();
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if (unlikely(pte.pte_low != ptep->pte_low))
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goto retry;
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return pte;
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#endif
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}
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static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
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{
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while ((*nr) - nr_start) {
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struct page *page = pages[--(*nr)];
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ClearPageReferenced(page);
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put_page(page);
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}
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}
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/*
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* 'pteval' can come from a pte, pmd, pud or p4d. We only check
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* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
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* same value on all 4 types.
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*/
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static inline int pte_allows_gup(unsigned long pteval, int write)
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{
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unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
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if (write)
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need_pte_bits |= _PAGE_RW;
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if ((pteval & need_pte_bits) != need_pte_bits)
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return 0;
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/* Check memory protection keys permissions. */
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if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
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return 0;
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return 1;
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}
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/*
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* The performance critical leaf functions are made noinline otherwise gcc
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* inlines everything into a single function which results in too much
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* register pressure.
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*/
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static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
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unsigned long end, int write, struct page **pages, int *nr)
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{
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struct dev_pagemap *pgmap = NULL;
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int nr_start = *nr, ret = 0;
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pte_t *ptep, *ptem;
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/*
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* Keep the original mapped PTE value (ptem) around since we
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* might increment ptep off the end of the page when finishing
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* our loop iteration.
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*/
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ptem = ptep = pte_offset_map(&pmd, addr);
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do {
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pte_t pte = gup_get_pte(ptep);
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struct page *page;
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/* Similar to the PMD case, NUMA hinting must take slow path */
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if (pte_protnone(pte))
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break;
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if (!pte_allows_gup(pte_val(pte), write))
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break;
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|
||||
if (pte_devmap(pte)) {
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pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
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if (unlikely(!pgmap)) {
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undo_dev_pagemap(nr, nr_start, pages);
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break;
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}
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} else if (pte_special(pte))
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break;
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VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
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page = pte_page(pte);
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get_page(page);
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put_dev_pagemap(pgmap);
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SetPageReferenced(page);
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pages[*nr] = page;
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(*nr)++;
|
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|
||||
} while (ptep++, addr += PAGE_SIZE, addr != end);
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if (addr == end)
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ret = 1;
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pte_unmap(ptem);
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|
||||
return ret;
|
||||
}
|
||||
|
||||
static inline void get_head_page_multiple(struct page *page, int nr)
|
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{
|
||||
VM_BUG_ON_PAGE(page != compound_head(page), page);
|
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VM_BUG_ON_PAGE(page_count(page) == 0, page);
|
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page_ref_add(page, nr);
|
||||
SetPageReferenced(page);
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||||
}
|
||||
|
||||
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
|
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unsigned long end, struct page **pages, int *nr)
|
||||
{
|
||||
int nr_start = *nr;
|
||||
struct dev_pagemap *pgmap = NULL;
|
||||
|
||||
do {
|
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struct page *page = pfn_to_page(pfn);
|
||||
|
||||
pgmap = get_dev_pagemap(pfn, pgmap);
|
||||
if (unlikely(!pgmap)) {
|
||||
undo_dev_pagemap(nr, nr_start, pages);
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||||
return 0;
|
||||
}
|
||||
SetPageReferenced(page);
|
||||
pages[*nr] = page;
|
||||
get_page(page);
|
||||
put_dev_pagemap(pgmap);
|
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(*nr)++;
|
||||
pfn++;
|
||||
} while (addr += PAGE_SIZE, addr != end);
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
|
||||
unsigned long end, struct page **pages, int *nr)
|
||||
{
|
||||
unsigned long fault_pfn;
|
||||
|
||||
fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
|
||||
return __gup_device_huge(fault_pfn, addr, end, pages, nr);
|
||||
}
|
||||
|
||||
static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
|
||||
unsigned long end, struct page **pages, int *nr)
|
||||
{
|
||||
unsigned long fault_pfn;
|
||||
|
||||
fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
|
||||
return __gup_device_huge(fault_pfn, addr, end, pages, nr);
|
||||
}
|
||||
|
||||
static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
|
||||
unsigned long end, int write, struct page **pages, int *nr)
|
||||
{
|
||||
struct page *head, *page;
|
||||
int refs;
|
||||
|
||||
if (!pte_allows_gup(pmd_val(pmd), write))
|
||||
return 0;
|
||||
|
||||
VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
|
||||
if (pmd_devmap(pmd))
|
||||
return __gup_device_huge_pmd(pmd, addr, end, pages, nr);
|
||||
|
||||
/* hugepages are never "special" */
|
||||
VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
|
||||
|
||||
refs = 0;
|
||||
head = pmd_page(pmd);
|
||||
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
|
||||
do {
|
||||
VM_BUG_ON_PAGE(compound_head(page) != head, page);
|
||||
pages[*nr] = page;
|
||||
(*nr)++;
|
||||
page++;
|
||||
refs++;
|
||||
} while (addr += PAGE_SIZE, addr != end);
|
||||
get_head_page_multiple(head, refs);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
|
||||
int write, struct page **pages, int *nr)
|
||||
{
|
||||
unsigned long next;
|
||||
pmd_t *pmdp;
|
||||
|
||||
pmdp = pmd_offset(&pud, addr);
|
||||
do {
|
||||
pmd_t pmd = *pmdp;
|
||||
|
||||
next = pmd_addr_end(addr, end);
|
||||
if (pmd_none(pmd))
|
||||
return 0;
|
||||
if (unlikely(pmd_large(pmd) || !pmd_present(pmd))) {
|
||||
/*
|
||||
* NUMA hinting faults need to be handled in the GUP
|
||||
* slowpath for accounting purposes and so that they
|
||||
* can be serialised against THP migration.
|
||||
*/
|
||||
if (pmd_protnone(pmd))
|
||||
return 0;
|
||||
if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
|
||||
return 0;
|
||||
} else {
|
||||
if (!gup_pte_range(pmd, addr, next, write, pages, nr))
|
||||
return 0;
|
||||
}
|
||||
} while (pmdp++, addr = next, addr != end);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
|
||||
unsigned long end, int write, struct page **pages, int *nr)
|
||||
{
|
||||
struct page *head, *page;
|
||||
int refs;
|
||||
|
||||
if (!pte_allows_gup(pud_val(pud), write))
|
||||
return 0;
|
||||
|
||||
VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
|
||||
if (pud_devmap(pud))
|
||||
return __gup_device_huge_pud(pud, addr, end, pages, nr);
|
||||
|
||||
/* hugepages are never "special" */
|
||||
VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
|
||||
|
||||
refs = 0;
|
||||
head = pud_page(pud);
|
||||
page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
|
||||
do {
|
||||
VM_BUG_ON_PAGE(compound_head(page) != head, page);
|
||||
pages[*nr] = page;
|
||||
(*nr)++;
|
||||
page++;
|
||||
refs++;
|
||||
} while (addr += PAGE_SIZE, addr != end);
|
||||
get_head_page_multiple(head, refs);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
|
||||
int write, struct page **pages, int *nr)
|
||||
{
|
||||
unsigned long next;
|
||||
pud_t *pudp;
|
||||
|
||||
pudp = pud_offset(&p4d, addr);
|
||||
do {
|
||||
pud_t pud = *pudp;
|
||||
|
||||
next = pud_addr_end(addr, end);
|
||||
if (pud_none(pud))
|
||||
return 0;
|
||||
if (unlikely(pud_large(pud))) {
|
||||
if (!gup_huge_pud(pud, addr, next, write, pages, nr))
|
||||
return 0;
|
||||
} else {
|
||||
if (!gup_pmd_range(pud, addr, next, write, pages, nr))
|
||||
return 0;
|
||||
}
|
||||
} while (pudp++, addr = next, addr != end);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
|
||||
int write, struct page **pages, int *nr)
|
||||
{
|
||||
unsigned long next;
|
||||
p4d_t *p4dp;
|
||||
|
||||
p4dp = p4d_offset(&pgd, addr);
|
||||
do {
|
||||
p4d_t p4d = *p4dp;
|
||||
|
||||
next = p4d_addr_end(addr, end);
|
||||
if (p4d_none(p4d))
|
||||
return 0;
|
||||
BUILD_BUG_ON(p4d_large(p4d));
|
||||
if (!gup_pud_range(p4d, addr, next, write, pages, nr))
|
||||
return 0;
|
||||
} while (p4dp++, addr = next, addr != end);
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
|
||||
* back to the regular GUP.
|
||||
*/
|
||||
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
|
||||
struct page **pages)
|
||||
{
|
||||
struct mm_struct *mm = current->mm;
|
||||
unsigned long addr, len, end;
|
||||
unsigned long next;
|
||||
unsigned long flags;
|
||||
pgd_t *pgdp;
|
||||
int nr = 0;
|
||||
|
||||
start &= PAGE_MASK;
|
||||
addr = start;
|
||||
len = (unsigned long) nr_pages << PAGE_SHIFT;
|
||||
end = start + len;
|
||||
if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
|
||||
(void __user *)start, len)))
|
||||
return 0;
|
||||
|
||||
/*
|
||||
* XXX: batch / limit 'nr', to avoid large irq off latency
|
||||
* needs some instrumenting to determine the common sizes used by
|
||||
* important workloads (eg. DB2), and whether limiting the batch size
|
||||
* will decrease performance.
|
||||
*
|
||||
* It seems like we're in the clear for the moment. Direct-IO is
|
||||
* the main guy that batches up lots of get_user_pages, and even
|
||||
* they are limited to 64-at-a-time which is not so many.
|
||||
*/
|
||||
/*
|
||||
* This doesn't prevent pagetable teardown, but does prevent
|
||||
* the pagetables and pages from being freed on x86.
|
||||
*
|
||||
* So long as we atomically load page table pointers versus teardown
|
||||
* (which we do on x86, with the above PAE exception), we can follow the
|
||||
* address down to the the page and take a ref on it.
|
||||
*/
|
||||
local_irq_save(flags);
|
||||
pgdp = pgd_offset(mm, addr);
|
||||
do {
|
||||
pgd_t pgd = *pgdp;
|
||||
|
||||
next = pgd_addr_end(addr, end);
|
||||
if (pgd_none(pgd))
|
||||
break;
|
||||
if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
|
||||
break;
|
||||
} while (pgdp++, addr = next, addr != end);
|
||||
local_irq_restore(flags);
|
||||
|
||||
return nr;
|
||||
}
|
||||
|
||||
/**
|
||||
* get_user_pages_fast() - pin user pages in memory
|
||||
* @start: starting user address
|
||||
* @nr_pages: number of pages from start to pin
|
||||
* @write: whether pages will be written to
|
||||
* @pages: array that receives pointers to the pages pinned.
|
||||
* Should be at least nr_pages long.
|
||||
*
|
||||
* Attempt to pin user pages in memory without taking mm->mmap_sem.
|
||||
* If not successful, it will fall back to taking the lock and
|
||||
* calling get_user_pages().
|
||||
*
|
||||
* Returns number of pages pinned. This may be fewer than the number
|
||||
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
||||
* were pinned, returns -errno.
|
||||
*/
|
||||
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
|
||||
struct page **pages)
|
||||
{
|
||||
struct mm_struct *mm = current->mm;
|
||||
unsigned long addr, len, end;
|
||||
unsigned long next;
|
||||
pgd_t *pgdp;
|
||||
int nr = 0;
|
||||
|
||||
start &= PAGE_MASK;
|
||||
addr = start;
|
||||
len = (unsigned long) nr_pages << PAGE_SHIFT;
|
||||
|
||||
end = start + len;
|
||||
if (end < start)
|
||||
goto slow_irqon;
|
||||
|
||||
#ifdef CONFIG_X86_64
|
||||
if (end >> __VIRTUAL_MASK_SHIFT)
|
||||
goto slow_irqon;
|
||||
#endif
|
||||
|
||||
/*
|
||||
* XXX: batch / limit 'nr', to avoid large irq off latency
|
||||
* needs some instrumenting to determine the common sizes used by
|
||||
* important workloads (eg. DB2), and whether limiting the batch size
|
||||
* will decrease performance.
|
||||
*
|
||||
* It seems like we're in the clear for the moment. Direct-IO is
|
||||
* the main guy that batches up lots of get_user_pages, and even
|
||||
* they are limited to 64-at-a-time which is not so many.
|
||||
*/
|
||||
/*
|
||||
* This doesn't prevent pagetable teardown, but does prevent
|
||||
* the pagetables and pages from being freed on x86.
|
||||
*
|
||||
* So long as we atomically load page table pointers versus teardown
|
||||
* (which we do on x86, with the above PAE exception), we can follow the
|
||||
* address down to the the page and take a ref on it.
|
||||
*/
|
||||
local_irq_disable();
|
||||
pgdp = pgd_offset(mm, addr);
|
||||
do {
|
||||
pgd_t pgd = *pgdp;
|
||||
|
||||
next = pgd_addr_end(addr, end);
|
||||
if (pgd_none(pgd))
|
||||
goto slow;
|
||||
if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
|
||||
goto slow;
|
||||
} while (pgdp++, addr = next, addr != end);
|
||||
local_irq_enable();
|
||||
|
||||
VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
|
||||
return nr;
|
||||
|
||||
{
|
||||
int ret;
|
||||
|
||||
slow:
|
||||
local_irq_enable();
|
||||
slow_irqon:
|
||||
/* Try to get the remaining pages with get_user_pages */
|
||||
start += nr << PAGE_SHIFT;
|
||||
pages += nr;
|
||||
|
||||
ret = get_user_pages_unlocked(start,
|
||||
(end - start) >> PAGE_SHIFT,
|
||||
pages, write ? FOLL_WRITE : 0);
|
||||
|
||||
/* Have to be a bit careful with return values */
|
||||
if (nr > 0) {
|
||||
if (ret < 0)
|
||||
ret = nr;
|
||||
else
|
||||
ret += nr;
|
||||
}
|
||||
|
||||
return ret;
|
||||
}
|
||||
}
|
||||
|
|
@ -137,7 +137,7 @@ config HAVE_MEMBLOCK_NODE_MAP
|
|||
config HAVE_MEMBLOCK_PHYS_MAP
|
||||
bool
|
||||
|
||||
config HAVE_GENERIC_GUP
|
||||
config HAVE_GENERIC_RCU_GUP
|
||||
bool
|
||||
|
||||
config ARCH_DISCARD_MEMBLOCK
|
||||
|
|
|
|||
10
mm/gup.c
10
mm/gup.c
|
|
@ -1155,7 +1155,7 @@ struct page *get_dump_page(unsigned long addr)
|
|||
#endif /* CONFIG_ELF_CORE */
|
||||
|
||||
/*
|
||||
* Generic Fast GUP
|
||||
* Generic RCU Fast GUP
|
||||
*
|
||||
* get_user_pages_fast attempts to pin user pages by walking the page
|
||||
* tables directly and avoids taking locks. Thus the walker needs to be
|
||||
|
|
@ -1176,8 +1176,8 @@ struct page *get_dump_page(unsigned long addr)
|
|||
* Before activating this code, please be aware that the following assumptions
|
||||
* are currently made:
|
||||
*
|
||||
* *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
|
||||
* free pages containing page tables or TLB flushing requires IPI broadcast.
|
||||
* *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
|
||||
* pages containing page tables.
|
||||
*
|
||||
* *) ptes can be read atomically by the architecture.
|
||||
*
|
||||
|
|
@ -1187,7 +1187,7 @@ struct page *get_dump_page(unsigned long addr)
|
|||
*
|
||||
* This code is based heavily on the PowerPC implementation by Nick Piggin.
|
||||
*/
|
||||
#ifdef CONFIG_HAVE_GENERIC_GUP
|
||||
#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
|
||||
|
||||
#ifndef gup_get_pte
|
||||
/*
|
||||
|
|
@ -1677,4 +1677,4 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
|
|||
return ret;
|
||||
}
|
||||
|
||||
#endif /* CONFIG_HAVE_GENERIC_GUP */
|
||||
#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user