mm: handling Non-LRU pages returned by vm_normal_pages

With DEVICE_COHERENT, we'll soon have vm_normal_pages() return
device-managed anonymous pages that are not LRU pages.  Although they
behave like normal pages for purposes of mapping in CPU page, and for COW.
They do not support LRU lists, NUMA migration or THP.

Callers to follow_page() currently don't expect ZONE_DEVICE pages,
however, with DEVICE_COHERENT we might now return ZONE_DEVICE.  Check for
ZONE_DEVICE pages in applicable users of follow_page() as well.

Link: https://lkml.kernel.org/r/20220715150521.18165-5-alex.sierra@amd.com
Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>	[v2]
Reviewed-by: Alistair Popple <apopple@nvidia.com>	[v6]
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 751c19d..1d7fd83 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1795,7 +1795,7 @@ static struct page *can_gather_numa_stats(pte_t pte, struct vm_area_struct *vma,
                return NULL;
 
        page = vm_normal_page(vma, addr, pte);
-       if (!page)
+       if (!page || is_zone_device_page(page))
                return NULL;
 
        if (PageReserved(page))

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 60d742c..a563de8 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2910,7 +2910,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
 
                if (IS_ERR(page))
                        continue;
-               if (!page)
+               if (!page || is_zone_device_page(page))
                        continue;
 
                if (!is_transparent_hugepage(page))

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 01e0d63..dea1021 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -611,7 +611,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
                        goto out;
                }
                page = vm_normal_page(vma, address, pteval);
-               if (unlikely(!page)) {
+               if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
                        result = SCAN_PAGE_NULL;
                        goto out;
                }
@@ -1261,7 +1261,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
                        writable = true;
 
                page = vm_normal_page(vma, _address, pteval);
-               if (unlikely(!page)) {
+               if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
                        result = SCAN_PAGE_NULL;
                        goto out_unmap;
                }
@@ -1472,7 +1472,8 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
                        goto abort;
 
                page = vm_normal_page(vma, addr, *pte);
-
+               if (WARN_ON_ONCE(page && is_zone_device_page(page)))
+                       page = NULL;
                /*
                 * Note that uprobe, debugger, or MAP_PRIVATE may change the
                 * page table, but the new page will not be a subpage of hpage.
@@ -1490,6 +1491,8 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
                if (pte_none(*pte))
                        continue;
                page = vm_normal_page(vma, addr, *pte);
+               if (WARN_ON_ONCE(page && is_zone_device_page(page)))
+                       goto abort;
                page_remove_rmap(page, vma, false);
        }
 

diff --git a/mm/ksm.c b/mm/ksm.c
index 8d2dc50..55f1d96 100644 (file)
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
                cond_resched();
                page = follow_page(vma, addr,
                                FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
-               if (IS_ERR_OR_NULL(page))
+               if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
                        break;
                if (PageKsm(page))
                        ret = handle_mm_fault(vma, addr,
@@ -560,7 +560,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
                goto out;
 
        page = follow_page(vma, addr, FOLL_GET);
-       if (IS_ERR_OR_NULL(page))
+       if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
                goto out;
        if (PageAnon(page)) {
                flush_anon_page(vma, page, addr);
@@ -2308,7 +2308,7 @@ next_mm:
                        if (ksm_test_exit(mm))
                                break;
                        *page = follow_page(vma, ksm_scan.address, FOLL_GET);
-                       if (IS_ERR_OR_NULL(*page)) {
+                       if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) {
                                ksm_scan.address += PAGE_SIZE;
                                cond_resched();
                                continue;

diff --git a/mm/madvise.c b/mm/madvise.c
index e55108d..5f0f094 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -421,7 +421,7 @@ regular_page:
                        continue;
 
                page = vm_normal_page(vma, addr, ptent);
-               if (!page)
+               if (!page || is_zone_device_page(page))
                        continue;
 
                /*
@@ -639,7 +639,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
                }
 
                page = vm_normal_page(vma, addr, ptent);
-               if (!page)
+               if (!page || is_zone_device_page(page))
                        continue;
 
                /*

diff --git a/mm/memory.c b/mm/memory.c
index 580c62f..dce0b2e 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -624,6 +624,14 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
                if (is_zero_pfn(pfn))
                        return NULL;
                if (pte_devmap(pte))
+               /*
+                * NOTE: New users of ZONE_DEVICE will not set pte_devmap()
+                * and will have refcounts incremented on their struct pages
+                * when they are inserted into PTEs, thus they are safe to
+                * return here. Legacy ZONE_DEVICE pages that set pte_devmap()
+                * do not have refcounts. Example of legacy ZONE_DEVICE is
+                * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers.
+                */
                        return NULL;
 
                print_bad_pte(vma, addr, pte, NULL);
@@ -4693,7 +4701,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
        pte = pte_modify(old_pte, vma->vm_page_prot);
 
        page = vm_normal_page(vma, vmf->address, pte);
-       if (!page)
+       if (!page || is_zone_device_page(page))
                goto out_map;
 
        /* TODO: handle PTE-mapped THP */

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f4cd963..88a5173 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -523,7 +523,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
                if (!pte_present(*pte))
                        continue;
                page = vm_normal_page(vma, addr, *pte);
-               if (!page)
+               if (!page || is_zone_device_page(page))
                        continue;
                /*
                 * vm_normal_page() filters out zero pages, but there might

diff --git a/mm/migrate.c b/mm/migrate.c
index 7934eeb..1649270 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1630,7 +1630,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
                goto out;
 
        err = -ENOENT;
-       if (!page)
+       if (!page || is_zone_device_page(page))
                goto out;
 
        err = 0;
@@ -1821,7 +1821,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
                if (IS_ERR(page))
                        goto set_status;
 
-               if (page) {
+               if (page && !is_zone_device_page(page)) {
                        err = page_to_nid(page);
                        put_page(page);
                } else {

diff --git a/mm/mlock.c b/mm/mlock.c
index 716caf8..b14e929 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -333,7 +333,7 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
                if (!pte_present(*pte))
                        continue;
                page = vm_normal_page(vma, addr, *pte);
-               if (!page)
+               if (!page || is_zone_device_page(page))
                        continue;
                if (PageTransCompound(page))
                        continue;

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 996a97e..5ef478b 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -127,7 +127,7 @@ static unsigned long change_pte_range(struct mmu_gather *tlb,
                                        continue;
 
                                page = vm_normal_page(vma, addr, oldpte);
-                               if (!page || PageKsm(page))
+                               if (!page || is_zone_device_page(page) || PageKsm(page))
                                        continue;
 
                                /* Also skip shared copy-on-write pages */