[RFC,v2,02/30] mm: pagewalk: use READ_ONCE when reading the PMD entry unlocked

Message ID	20200928175428.4110504-3-zi.yan@sent.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=Qft/=DF=kvack.org=owner-linux-mm@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 46F9C2158C From: Zi Yan <zi.yan@sent.com> To: linux-mm@kvack.org Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>, Matthew Wilcox <willy@infradead.org>, Shakeel Butt <shakeelb@google.com>, Yang Shi <shy828301@gmail.com>, Jason Gunthorpe <jgg@nvidia.com>, Mike Kravetz <mike.kravetz@oracle.com>, Michal Hocko <mhocko@suse.com>, David Hildenbrand <david@redhat.com>, William Kucharski <william.kucharski@oracle.com>, Andrea Arcangeli <aarcange@redhat.com>, John Hubbard <jhubbard@nvidia.com>, David Nellans <dnellans@nvidia.com>, linux-kernel@vger.kernel.org, Zi Yan <ziy@nvidia.com> Subject: [RFC PATCH v2 02/30] mm: pagewalk: use READ_ONCE when reading the PMD entry unlocked Date: Mon, 28 Sep 2020 13:54:00 -0400 Message-Id: <20200928175428.4110504-3-zi.yan@sent.com> In-Reply-To: <20200928175428.4110504-1-zi.yan@sent.com> References: <20200928175428.4110504-1-zi.yan@sent.com> Reply-To: Zi Yan <ziy@nvidia.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	1GB PUD THP support on x86_64 \| expand [RFC,v2,00/30] 1GB PUD THP support on x86_64 [RFC,v2,01/30] mm/pagewalk: use READ_ONCE when reading the PUD entry unlocked [RFC,v2,02/30] mm: pagewalk: use READ_ONCE when reading the PMD entry unlocked [RFC,v2,03/30] mm: thp: use single linked list for THP page table page deposit. [RFC,v2,04/30] mm: add new helper functions to allocate one PMD page with 512 PTE pages. [RFC,v2,05/30] mm: thp: add page table deposit/withdraw functions for PUD THP. [RFC,v2,06/30] mm: change thp_order and thp_nr as we will have not just PMD THPs. [RFC,v2,07/30] mm: thp: add anonymous PUD THP page fault support without enabling it. [RFC,v2,08/30] mm: thp: add PUD THP support for copy_huge_pud. [RFC,v2,09/30] mm: thp: add PUD THP support to zap_huge_pud. [RFC,v2,10/30] fs: proc: add PUD THP kpageflag. [RFC,v2,11/30] mm: thp: handling PUD THP reference bit. [RFC,v2,12/30] mm: rmap: add mappped/unmapped page order to anonymous page rmap functions. [RFC,v2,13/30] mm: rmap: add map_order to page_remove_anon_compound_rmap. [RFC,v2,14/30] mm: thp: add PUD THP split_huge_pud_page() function. [RFC,v2,15/30] mm: thp: add PUD THP to deferred split list when PUD mapping is gone. [RFC,v2,16/30] mm: debug: adapt dump_page to PUD THP. [RFC,v2,17/30] mm: thp: PUD THP COW splits PUD page and falls back to PMD page. [RFC,v2,18/30] mm: thp: PUD THP follow_p*d_page() support. [RFC,v2,19/30] mm: stats: make smap stats understand PUD THPs. [RFC,v2,20/30] mm: page_vma_walk: teach it about PMD-mapped PUD THP. [RFC,v2,21/30] mm: thp: PUD THP support in try_to_unmap(). [RFC,v2,22/30] mm: thp: split PUD THPs at page reclaim. [RFC,v2,23/30] mm: support PUD THP pagemap support. [RFC,v2,24/30] mm: madvise: add page size options to MADV_HUGEPAGE and MADV_NOHUGEPAGE. [RFC,v2,25/30] mm: vma: add VM_HUGEPAGE_PUD to vm_flags at bit 37. [RFC,v2,26/30] mm: thp: add a global knob to enable/disable PUD THPs. [RFC,v2,27/30] mm: thp: make PUD THP size public. [RFC,v2,28/30] hugetlb: cma: move cma reserve function to cma.c. [RFC,v2,29/30] mm: thp: use cma reservation for pud thp allocation. [RFC,v2,30/30] mm: thp: enable anonymous PUD THP at page fault path.

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 069978777423..a21484b1414d 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -570,28 +570,33 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr, } #endif -static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, - struct mm_walk *walk) +static int smaps_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->vma; pte_t *pte; spinlock_t *ptl; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { - smaps_pmd_entry(pmd, addr, walk); + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } + smaps_pmd_entry(pmdp, addr, walk); spin_unlock(ptl); goto out; } - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) goto out; /* * The mmap_lock held all the way back in m_start() is what * keeps khugepaged out of here and from collapsing things * in here. */ - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) smaps_pte_entry(pte, addr, walk); pte_unmap_unlock(pte - 1, ptl); @@ -1091,7 +1096,7 @@ static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma, } #endif -static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, +static int clear_refs_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { struct clear_refs_private *cp = walk->private; @@ -1100,20 +1105,25 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, spinlock_t *ptl; struct page *page; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } if (cp->type == CLEAR_REFS_SOFT_DIRTY) { - clear_soft_dirty_pmd(vma, addr, pmd); + clear_soft_dirty_pmd(vma, addr, pmdp); goto out; } - if (!pmd_present(*pmd)) + if (!pmd_present(pmd)) goto out; - page = pmd_page(*pmd); + page = pmd_page(pmd); /* Clear accessed and referenced bits. */ - pmdp_test_and_clear_young(vma, addr, pmd); + pmdp_test_and_clear_young(vma, addr, pmdp); test_and_clear_page_young(page); ClearPageReferenced(page); out: @@ -1121,10 +1131,10 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, return 0; } - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { ptent = *pte; @@ -1388,8 +1398,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm, return make_pme(frame, flags); } -static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, - struct mm_walk *walk) +static int pagemap_pmd_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->vma; struct pagemapread *pm = walk->private; @@ -1401,9 +1411,14 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { u64 flags = 0, frame = 0; - pmd_t pmd = *pmdp; struct page *page = NULL; + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } + if (vma->vm_flags & VM_SOFTDIRTY) flags |= PM_SOFT_DIRTY; @@ -1456,7 +1471,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, return err; } - if (pmd_trans_unstable(pmdp)) + if (pmd_trans_unstable(&pmd)) return 0; #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ @@ -1768,7 +1783,7 @@ static struct page *can_gather_numa_stats_pmd(pmd_t pmd, } #endif -static int gather_pte_stats(pmd_t *pmd, unsigned long addr, +static int gather_pte_stats(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { struct numa_maps *md = walk->private; @@ -1778,22 +1793,28 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr, pte_t *pte; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { struct page *page; - page = can_gather_numa_stats_pmd(*pmd, vma, addr); + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } + + page = can_gather_numa_stats_pmd(pmd, vma, addr); if (page) - gather_stats(page, md, pmd_dirty(*pmd), + gather_stats(page, md, pmd_dirty(pmd), HPAGE_PMD_SIZE/PAGE_SIZE); spin_unlock(ptl); return 0; } - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; #endif - orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + orig_pte = pte = pte_offset_map_lock(walk->mm, pmdp, addr, &ptl); do { struct page *page = can_gather_numa_stats(*pte, vma, addr); if (!page) diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h index 6caf28aadafb..686b57e94a9f 100644 --- a/include/linux/pagewalk.h +++ b/include/linux/pagewalk.h @@ -41,7 +41,7 @@ struct mm_walk_ops { unsigned long next, struct mm_walk *walk); int (*pud_entry)(pud_t pud, pud_t *pudp, unsigned long addr, unsigned long next, struct mm_walk *walk); - int (*pmd_entry)(pmd_t *pmd, unsigned long addr, + int (*pmd_entry)(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long next, struct mm_walk *walk); int (*pte_entry)(pte_t *pte, unsigned long addr, unsigned long next, struct mm_walk *walk); diff --git a/mm/madvise.c b/mm/madvise.c index ae266dfede8a..16e7b8eadb13 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -183,14 +183,14 @@ static long madvise_behavior(struct vm_area_struct *vma, } #ifdef CONFIG_SWAP -static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, +static int swapin_walk_pmd_entry(pmd_t pmd, pmd_t *pmdp, unsigned long start, unsigned long end, struct mm_walk *walk) { pte_t *orig_pte; struct vm_area_struct *vma = walk->private; unsigned long index; - if (pmd_none_or_trans_huge_or_clear_bad(pmd)) + if (pmd_none_or_trans_huge_or_clear_bad(&pmd)) return 0; for (index = start; index != end; index += PAGE_SIZE) { @@ -199,7 +199,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, struct page *page; spinlock_t *ptl; - orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); + orig_pte = pte_offset_map_lock(vma->vm_mm, pmdp, start, &ptl); pte = *(orig_pte + ((index - start) / PAGE_SIZE)); pte_unmap_unlock(orig_pte, ptl); @@ -304,7 +304,7 @@ static long madvise_willneed(struct vm_area_struct *vma, return 0; } -static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, +static int madvise_cold_or_pageout_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { @@ -322,26 +322,29 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, return -EINTR; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (pmd_trans_huge(*pmd)) { - pmd_t orig_pmd; + if (pmd_trans_huge(pmd)) { unsigned long next = pmd_addr_end(addr, end); tlb_change_page_size(tlb, HPAGE_PMD_SIZE); - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (!ptl) return 0; - orig_pmd = *pmd; - if (is_huge_zero_pmd(orig_pmd)) + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + goto huge_unlock; + } + + if (is_huge_zero_pmd(pmd)) goto huge_unlock; - if (unlikely(!pmd_present(orig_pmd))) { + if (unlikely(!pmd_present(pmd))) { VM_BUG_ON(thp_migration_supported() && - !is_pmd_migration_entry(orig_pmd)); + !is_pmd_migration_entry(pmd)); goto huge_unlock; } - page = pmd_page(orig_pmd); + page = pmd_page(pmd); /* Do not interfere with other mappings of this page */ if (page_mapcount(page) != 1) @@ -361,12 +364,12 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, return 0; } - if (pmd_young(orig_pmd)) { - pmdp_invalidate(vma, addr, pmd); - orig_pmd = pmd_mkold(orig_pmd); + if (pmd_young(pmd)) { + pmdp_invalidate(vma, addr, pmdp); + pmd = pmd_mkold(pmd); - set_pmd_at(mm, addr, pmd, orig_pmd); - tlb_remove_pmd_tlb_entry(tlb, pmd, addr); + set_pmd_at(mm, addr, pmdp, pmd); + tlb_remove_pmd_tlb_entry(tlb, pmdp, addr); } ClearPageReferenced(page); @@ -388,11 +391,11 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, } regular_page: - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; #endif tlb_change_page_size(tlb, PAGE_SIZE); - orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); flush_tlb_batched_pending(mm); arch_enter_lazy_mmu_mode(); for (; addr < end; pte++, addr += PAGE_SIZE) { @@ -424,12 +427,12 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (split_huge_page(page)) { unlock_page(page); put_page(page); - pte_offset_map_lock(mm, pmd, addr, &ptl); + pte_offset_map_lock(mm, pmdp, addr, &ptl); break; } unlock_page(page); put_page(page); - pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(mm, pmdp, addr, &ptl); pte--; addr -= PAGE_SIZE; continue; @@ -566,7 +569,7 @@ static long madvise_pageout(struct vm_area_struct *vma, return 0; } -static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, +static int madvise_free_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { @@ -580,15 +583,15 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, unsigned long next; next = pmd_addr_end(addr, end); - if (pmd_trans_huge(*pmd)) - if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next)) + if (pmd_trans_huge(pmd)) + if (madvise_free_huge_pmd(tlb, vma, pmdp, addr, next)) goto next; - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; tlb_change_page_size(tlb, PAGE_SIZE); - orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + orig_pte = pte = pte_offset_map_lock(mm, pmdp, addr, &ptl); flush_tlb_batched_pending(mm); arch_enter_lazy_mmu_mode(); for (; addr != end; pte++, addr += PAGE_SIZE) { @@ -634,12 +637,12 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, if (split_huge_page(page)) { unlock_page(page); put_page(page); - pte_offset_map_lock(mm, pmd, addr, &ptl); + pte_offset_map_lock(mm, pmdp, addr, &ptl); goto out; } unlock_page(page); put_page(page); - pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(mm, pmdp, addr, &ptl); pte--; addr -= PAGE_SIZE; continue; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9c4a0851348f..b28f620c1c5b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5827,7 +5827,7 @@ static inline enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma, } #endif -static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, +static int mem_cgroup_count_precharge_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { @@ -5835,22 +5835,27 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, pte_t *pte; spinlock_t *ptl; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } /* * Note their can not be MC_TARGET_DEVICE for now as we do not * support transparent huge page with MEMORY_DEVICE_PRIVATE but * this might change. */ - if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE) + if (get_mctgt_type_thp(vma, addr, pmd, NULL) == MC_TARGET_PAGE) mc.precharge += HPAGE_PMD_NR; spin_unlock(ptl); return 0; } - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) if (get_mctgt_type(vma, addr, *pte, NULL)) mc.precharge++; /* increment precharge temporarily */ @@ -6023,7 +6028,7 @@ static void mem_cgroup_cancel_attach(struct cgroup_taskset *tset) mem_cgroup_clear_mc(); } -static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, +static int mem_cgroup_move_charge_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { @@ -6035,13 +6040,18 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, union mc_target target; struct page *page; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } if (mc.precharge < HPAGE_PMD_NR) { spin_unlock(ptl); return 0; } - target_type = get_mctgt_type_thp(vma, addr, *pmd, &target); + target_type = get_mctgt_type_thp(vma, addr, pmd, &target); if (target_type == MC_TARGET_PAGE) { page = target.page; if (!isolate_lru_page(page)) { @@ -6066,10 +6076,10 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, return 0; } - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; retry: - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); for (; addr != end; addr += PAGE_SIZE) { pte_t ptent = *(pte++); bool device = false; diff --git a/mm/mempolicy.c b/mm/mempolicy.c index eddbe4e56c73..731a7710395f 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -516,7 +516,7 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr, * -EIO - only MPOL_MF_STRICT was specified and an existing page was already * on a node that does not follow the policy. */ -static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, +static int queue_pages_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->vma; @@ -528,18 +528,23 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, pte_t *pte; spinlock_t *ptl; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { - ret = queue_pages_pmd(pmd, ptl, addr, end, walk); + if (memcmp(pmdp, &pmd, sizeof(pmd)) != 0) { + walk->action = ACTION_AGAIN; + spin_unlock(ptl); + return 0; + } + ret = queue_pages_pmd(pmdp, ptl, addr, end, walk); if (ret != 2) return ret; } /* THP was split, fall through to pte walk */ - if (pmd_trans_unstable(pmd)) + if (pmd_trans_unstable(&pmd)) return 0; - pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + pte = pte_offset_map_lock(walk->mm, pmdp, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { if (!pte_present(*pte)) continue; diff --git a/mm/mincore.c b/mm/mincore.c index 02db1a834021..168661f32aaa 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -96,8 +96,8 @@ static int mincore_unmapped_range(unsigned long addr, unsigned long end, return 0; } -static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, - struct mm_walk *walk) +static int mincore_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, struct mm_walk *walk) { spinlock_t *ptl; struct vm_area_struct *vma = walk->vma; @@ -105,19 +105,19 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, unsigned char *vec = walk->private; int nr = (end - addr) >> PAGE_SHIFT; - ptl = pmd_trans_huge_lock(pmd, vma); + ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { memset(vec, 1, nr); spin_unlock(ptl); goto out; } - if (pmd_trans_unstable(pmd)) { + if (pmd_trans_unstable(&pmd)) { __mincore_unmapped_range(addr, end, vma, vec); goto out; } - ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + ptep = pte_offset_map_lock(walk->mm, pmdp, addr, &ptl); for (; addr != end; ptep++, addr += PAGE_SIZE) { pte_t pte = *ptep; diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 15d1e423b4a3..a3752c82a7b2 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -61,17 +61,19 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, static int walk_pmd_range(pud_t pud, unsigned long addr, unsigned long end, struct mm_walk *walk) { - pmd_t *pmd; + pmd_t *pmdp; + pmd_t pmd; unsigned long next; const struct mm_walk_ops *ops = walk->ops; int err = 0; int depth = real_depth(3); - pmd = pmd_offset(&pud, addr); + pmdp = pmd_offset(&pud, addr); do { again: + pmd = READ_ONCE(*pmdp); next = pmd_addr_end(addr, end); - if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) { + if (pmd_none(pmd) || (!walk->vma && !walk->no_vma)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) @@ -86,7 +88,7 @@ static int walk_pmd_range(pud_t pud, unsigned long addr, unsigned long end, * needs to know about pmd_trans_huge() pmds */ if (ops->pmd_entry) - err = ops->pmd_entry(pmd, addr, next, walk); + err = ops->pmd_entry(pmd, pmdp, addr, next, walk); if (err) break; @@ -97,21 +99,22 @@ static int walk_pmd_range(pud_t pud, unsigned long addr, unsigned long end, * Check this here so we only break down trans_huge * pages when we _need_ to */ - if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) || + if ((!walk->vma && (pmd_leaf(pmd) || !pmd_present(pmd))) || walk->action == ACTION_CONTINUE || !(ops->pte_entry)) continue; if (walk->vma) { - split_huge_pmd(walk->vma, pmd, addr); - if (pmd_trans_unstable(pmd)) + split_huge_pmd(walk->vma, pmdp, addr); + pmd = READ_ONCE(*pmdp); + if (pmd_trans_unstable(&pmd)) goto again; } - err = walk_pte_range(pmd, addr, next, walk); + err = walk_pte_range(pmdp, addr, next, walk); if (err) break; - } while (pmd++, addr = next, addr != end); + } while (pmdp++, addr = next, addr != end); return err; }

[RFC,v2,02/30] mm: pagewalk: use READ_ONCE when reading the PMD entry unlocked

Commit Message

Patch