mm/rmap: fail try_to_migrate() early when setting a PMD migration entry fails

Let's fail right away in case we cannot clear PG_anon_exclusive because
the anon THP may be pinned.  Right now, we continue trying to install
migration entries and the caller of try_to_migrate() will realize that the
page is still mapped and has to restore the migration entries.  Let's just
fail fast just like for PTE migration entries.

Link: https://lkml.kernel.org/r/20220428083441.37290-14-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 6648b97..e476a8f 100644 (file)
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -299,7 +299,7 @@ static inline bool is_pfn_swap_entry(swp_entry_t entry)
 struct page_vma_mapped_walk;
 
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
-extern void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
+extern int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
                struct page *page);
 
 extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
@@ -332,7 +332,7 @@ static inline int is_pmd_migration_entry(pmd_t pmd)
        return !pmd_present(pmd) && is_migration_entry(pmd_to_swp_entry(pmd));
 }
 #else
-static inline void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
+static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
                struct page *page)
 {
        BUILD_BUG();

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 231911b..14d7fa6 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3066,7 +3066,7 @@ late_initcall(split_huge_pages_debugfs);
 #endif
 
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
-void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
+int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
                struct page *page)
 {
        struct vm_area_struct *vma = pvmw->vma;
@@ -3078,7 +3078,7 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
        pmd_t pmdswp;
 
        if (!(pvmw->pmd && !pvmw->pte))
-               return;
+               return 0;
 
        flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
        pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
@@ -3086,7 +3086,7 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
        anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
        if (anon_exclusive && page_try_share_anon_rmap(page)) {
                set_pmd_at(mm, address, pvmw->pmd, pmdval);
-               return;
+               return -EBUSY;
        }
 
        if (pmd_dirty(pmdval))
@@ -3104,6 +3104,8 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
        page_remove_rmap(page, vma, true);
        put_page(page);
        trace_set_migration_pmd(address, pmd_val(pmdswp));
+
+       return 0;
 }
 
 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)

diff --git a/mm/rmap.c b/mm/rmap.c
index 0d63e7c..f96cc7e 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1856,7 +1856,11 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
                        VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
                                        !folio_test_pmd_mappable(folio), folio);
 
-                       set_pmd_migration_entry(&pvmw, subpage);
+                       if (set_pmd_migration_entry(&pvmw, subpage)) {
+                               ret = false;
+                               page_vma_mapped_walk_done(&pvmw);
+                               break;
+                       }
                        continue;
                }
 #endif