Commit 895f5ee4 authored by Hugh Dickins's avatar Hugh Dickins Committed by Andrew Morton
Browse files

mm/khugepaged: allow pte_offset_map[_lock]() to fail 

__collapse_huge_page_swapin(): don't drop the map after every pte, it only
has to be dropped by do_swap_page(); give up if pte_offset_map() fails;
trace_mm_collapse_huge_page_swapin() at the end, with result; fix comment
on returned result; fix vmf.pgoff, though it's not used.

collapse_huge_page(): use pte_offset_map_lock() on the _pmd returned from
clearing; allow failure, but it should be impossible there. 
hpage_collapse_scan_pmd() and collapse_pte_mapped_thp() allow for
pte_offset_map_lock() failure.

Link: https://lkml.kernel.org/r/6513e85-d798-34ec-3762-7c24ffb9329@google.com


Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c9c1ee20

mm/khugepaged.c

+49 −23
Original line number Diff line number Diff line
@@ -991,9 +991,8 @@ static int check_pmd_still_valid(struct mm_struct *mm, 
 * Only done if hpage_collapse_scan_pmd believes it is worthwhile.

 *

 * Called and returns without pte mapped or spinlocks held.

 * Note that if false is returned, mmap_lock will be released.

 * Returns result: if not SCAN_SUCCEED, mmap_lock has been released.

 */



static int __collapse_huge_page_swapin(struct mm_struct *mm,

				       struct vm_area_struct *vma,

				       unsigned long haddr, pmd_t *pmd,
@@ -1002,23 +1001,35 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm, 
	int swapped_in = 0;

	vm_fault_t ret = 0;

	unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);

	int result;

	pte_t *pte = NULL;



	for (address = haddr; address < end; address += PAGE_SIZE) {

		struct vm_fault vmf = {

			.vma = vma,

			.address = address,

			.pgoff = linear_page_index(vma, haddr),

			.pgoff = linear_page_index(vma, address),

			.flags = FAULT_FLAG_ALLOW_RETRY,

			.pmd = pmd,

		};



		vmf.pte = pte_offset_map(pmd, address);

		vmf.orig_pte = *vmf.pte;

		if (!is_swap_pte(vmf.orig_pte)) {

			pte_unmap(vmf.pte);

			continue;

		if (!pte++) {

			pte = pte_offset_map(pmd, address);

			if (!pte) {

				mmap_read_unlock(mm);

				result = SCAN_PMD_NULL;

				goto out;

			}

		}



		vmf.orig_pte = *pte;

		if (!is_swap_pte(vmf.orig_pte))

			continue;



		vmf.pte = pte;

		ret = do_swap_page(&vmf);

		/* Which unmaps pte (after perhaps re-checking the entry) */

		pte = NULL;



		/*

		 * do_swap_page returns VM_FAULT_RETRY with released mmap_lock.
@@ -1027,24 +1038,29 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm, 
		 * resulting in later failure.

		 */

		if (ret & VM_FAULT_RETRY) {

			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

			/* Likely, but not guaranteed, that page lock failed */

			return SCAN_PAGE_LOCK;

			result = SCAN_PAGE_LOCK;

			goto out;

		}

		if (ret & VM_FAULT_ERROR) {

			mmap_read_unlock(mm);

			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

			return SCAN_FAIL;

			result = SCAN_FAIL;

			goto out;

		}

		swapped_in++;

	}



	if (pte)

		pte_unmap(pte);



	/* Drain LRU add pagevec to remove extra pin on the swapped in pages */

	if (swapped_in)

		lru_add_drain();



	trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);

	return SCAN_SUCCEED;

	result = SCAN_SUCCEED;

out:

	trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result);

	return result;

}



static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
@@ -1144,9 +1160,6 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, 
				address + HPAGE_PMD_SIZE);

	mmu_notifier_invalidate_range_start(&range);



	pte = pte_offset_map(pmd, address);

	pte_ptl = pte_lockptr(mm, pmd);



	pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */

	/*

	 * This removes any huge TLB entry from the CPU so we won't allow
@@ -1161,12 +1174,17 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, 
	mmu_notifier_invalidate_range_end(&range);

	tlb_remove_table_sync_one();



	spin_lock(pte_ptl);

	pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);

	if (pte) {

		result = __collapse_huge_page_isolate(vma, address, pte, cc,

						      &compound_pagelist);

		spin_unlock(pte_ptl);

	} else {

		result = SCAN_PMD_NULL;

	}



	if (unlikely(result != SCAN_SUCCEED)) {

		if (pte)

			pte_unmap(pte);

		spin_lock(pmd_ptl);

		BUG_ON(!pmd_none(*pmd));
@@ -1251,6 +1269,11 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, 
	memset(cc->node_load, 0, sizeof(cc->node_load));

	nodes_clear(cc->alloc_nmask);

	pte = pte_offset_map_lock(mm, pmd, address, &ptl);

	if (!pte) {

		result = SCAN_PMD_NULL;

		goto out;

	}



	for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;

	     _pte++, _address += PAGE_SIZE) {

		pte_t pteval = *_pte;
@@ -1620,8 +1643,10 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, 
	 * lockless_pages_from_mm() and the hardware page walker can access page

	 * tables while all the high-level locks are held in write mode.

	 */

	start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);

	result = SCAN_FAIL;

	start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);

	if (!start_pte)

		goto drop_immap;



	/* step 1: check all mapped PTEs are to the right huge page */

	for (i = 0, addr = haddr, pte = start_pte;
@@ -1695,6 +1720,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, 


abort:

	pte_unmap_unlock(start_pte, ptl);

drop_immap:

	i_mmap_unlock_write(vma->vm_file->f_mapping);

	goto drop_hpage;

}