diff options
| -rw-r--r-- | arch/x86/kernel/vm86_32.c | 2 | ||||
| -rw-r--r-- | fs/proc/task_mmu.c | 9 | ||||
| -rw-r--r-- | include/asm-generic/pgtable.h | 61 | ||||
| -rw-r--r-- | mm/memcontrol.c | 4 | ||||
| -rw-r--r-- | mm/memory.c | 16 | ||||
| -rw-r--r-- | mm/mempolicy.c | 2 | ||||
| -rw-r--r-- | mm/mincore.c | 2 | ||||
| -rw-r--r-- | mm/pagewalk.c | 2 | ||||
| -rw-r--r-- | mm/swapfile.c | 4 |
9 files changed, 92 insertions, 10 deletions
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c index b466cab5ba15..328cb37bb827 100644 --- a/arch/x86/kernel/vm86_32.c +++ b/arch/x86/kernel/vm86_32.c @@ -172,6 +172,7 @@ static void mark_screen_rdonly(struct mm_struct *mm) spinlock_t *ptl; int i; + down_write(&mm->mmap_sem); pgd = pgd_offset(mm, 0xA0000); if (pgd_none_or_clear_bad(pgd)) goto out; @@ -190,6 +191,7 @@ static void mark_screen_rdonly(struct mm_struct *mm) } pte_unmap_unlock(pte, ptl); out: + up_write(&mm->mmap_sem); flush_tlb(); } diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 7dcd2a250495..3efa7253523e 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -409,6 +409,9 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, } else { spin_unlock(&walk->mm->page_table_lock); } + + if (pmd_trans_unstable(pmd)) + return 0; /* * The mmap_sem held all the way back in m_start() is what * keeps khugepaged out of here and from collapsing things @@ -507,6 +510,8 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, struct page *page; split_huge_page_pmd(walk->mm, pmd); + if (pmd_trans_unstable(pmd)) + return 0; pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { @@ -670,6 +675,8 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, int err = 0; split_huge_page_pmd(walk->mm, pmd); + if (pmd_trans_unstable(pmd)) + return 0; /* find the first VMA at or above 'addr' */ vma = find_vma(walk->mm, addr); @@ -961,6 +968,8 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr, spin_unlock(&walk->mm->page_table_lock); } + if (pmd_trans_unstable(pmd)) + return 0; orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); do { struct page *page = can_gather_numa_stats(*pte, md->vma, addr); diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 76bff2bff15e..a03c098b0cce 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -425,6 +425,8 @@ extern void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn, unsigned long size); #endif +#ifdef CONFIG_MMU + #ifndef CONFIG_TRANSPARENT_HUGEPAGE static inline int pmd_trans_huge(pmd_t pmd) { @@ -441,7 +443,66 @@ static inline int pmd_write(pmd_t pmd) return 0; } #endif /* __HAVE_ARCH_PMD_WRITE */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + +/* + * This function is meant to be used by sites walking pagetables with + * the mmap_sem hold in read mode to protect against MADV_DONTNEED and + * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd + * into a null pmd and the transhuge page fault can convert a null pmd + * into an hugepmd or into a regular pmd (if the hugepage allocation + * fails). While holding the mmap_sem in read mode the pmd becomes + * stable and stops changing under us only if it's not null and not a + * transhuge pmd. When those races occurs and this function makes a + * difference vs the standard pmd_none_or_clear_bad, the result is + * undefined so behaving like if the pmd was none is safe (because it + * can return none anyway). The compiler level barrier() is critically + * important to compute the two checks atomically on the same pmdval. + */ +static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd) +{ + /* depend on compiler for an atomic pmd read */ + pmd_t pmdval = *pmd; + /* + * The barrier will stabilize the pmdval in a register or on + * the stack so that it will stop changing under the code. + */ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + barrier(); +#endif + if (pmd_none(pmdval)) + return 1; + if (unlikely(pmd_bad(pmdval))) { + if (!pmd_trans_huge(pmdval)) + pmd_clear_bad(pmd); + return 1; + } + return 0; +} + +/* + * This is a noop if Transparent Hugepage Support is not built into + * the kernel. Otherwise it is equivalent to + * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in + * places that already verified the pmd is not none and they want to + * walk ptes while holding the mmap sem in read mode (write mode don't + * need this). If THP is not enabled, the pmd can't go away under the + * code even if MADV_DONTNEED runs, but if THP is enabled we need to + * run a pmd_trans_unstable before walking the ptes after + * split_huge_page_pmd returns (because it may have run when the pmd + * become null, but then a page fault can map in a THP and not a + * regular page). + */ +static inline int pmd_trans_unstable(pmd_t *pmd) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + return pmd_none_or_trans_huge_or_clear_bad(pmd); +#else + return 0; #endif +} + +#endif /* CONFIG_MMU */ #endif /* !__ASSEMBLY__ */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 26c6f4ec20f4..37281816ff67 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5230,6 +5230,8 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, spinlock_t *ptl; split_huge_page_pmd(walk->mm, pmd); + if (pmd_trans_unstable(pmd)) + return 0; pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) @@ -5390,6 +5392,8 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, spinlock_t *ptl; split_huge_page_pmd(walk->mm, pmd); + if (pmd_trans_unstable(pmd)) + return 0; retry: pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; addr += PAGE_SIZE) { diff --git a/mm/memory.c b/mm/memory.c index 347e5fad1cfa..e01abb908b6b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1247,16 +1247,24 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, do { next = pmd_addr_end(addr, end); if (pmd_trans_huge(*pmd)) { - if (next-addr != HPAGE_PMD_SIZE) { + if (next - addr != HPAGE_PMD_SIZE) { VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem)); split_huge_page_pmd(vma->vm_mm, pmd); } else if (zap_huge_pmd(tlb, vma, pmd, addr)) - continue; + goto next; /* fall through */ } - if (pmd_none_or_clear_bad(pmd)) - continue; + /* + * Here there can be other concurrent MADV_DONTNEED or + * trans huge page faults running, and if the pmd is + * none or trans huge it can change under us. This is + * because MADV_DONTNEED holds the mmap_sem in read + * mode. + */ + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) + goto next; next = zap_pte_range(tlb, vma, pmd, addr, next, details); +next: cond_resched(); } while (pmd++, addr = next, addr != end); diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 47296fee23db..0a3757067631 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -512,7 +512,7 @@ static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud, do { next = pmd_addr_end(addr, end); split_huge_page_pmd(vma->vm_mm, pmd); - if (pmd_none_or_clear_bad(pmd)) + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) continue; if (check_pte_range(vma, pmd, addr, next, nodes, flags, private)) diff --git a/mm/mincore.c b/mm/mincore.c index 636a86876ff2..936b4cee8cb1 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -164,7 +164,7 @@ static void mincore_pmd_range(struct vm_area_struct *vma, pud_t *pud, } /* fall through */ } - if (pmd_none_or_clear_bad(pmd)) + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) mincore_unmapped_range(vma, addr, next, vec); else mincore_pte_range(vma, pmd, addr, next, vec); diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 2f5cf10ff660..aa9701e12714 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -59,7 +59,7 @@ again: continue; split_huge_page_pmd(walk->mm, pmd); - if (pmd_none_or_clear_bad(pmd)) + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) goto again; err = walk_pte_range(pmd, addr, next, walk); if (err) diff --git a/mm/swapfile.c b/mm/swapfile.c index 00a962caab1a..44595a373e42 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -932,9 +932,7 @@ static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, pmd = pmd_offset(pud, addr); do { next = pmd_addr_end(addr, end); - if (unlikely(pmd_trans_huge(*pmd))) - continue; - if (pmd_none_or_clear_bad(pmd)) + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) continue; ret = unuse_pte_range(vma, pmd, addr, next, entry, page); if (ret) |
