powerpc: add pte_free_defer() for pgtables sharing page

Add powerpc-specific pte_free_defer(), to free table page via call_rcu().
pte_free_defer() will be called inside khugepaged's retract_page_tables()
loop, where allocating extra memory cannot be relied upon.  This precedes
the generic version to avoid build breakage from incompatible pgtable_t.

This is awkward because the struct page contains only one rcu_head, but
that page may be shared between PTE_FRAG_NR pagetables, each wanting to
use the rcu_head at the same time.  But powerpc never reuses a fragment
once it has been freed: so mark the page Active in pte_free_defer(),
before calling pte_fragment_free() directly; and there call_rcu() to
pte_free_now() when last fragment is freed and the page is PageActive.

Link: https://lkml.kernel.org/r/6e3ca5f1-334d-4b14-b92d-fc8e99914fcb@google.com
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
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: Russell King <linux@armlinux.org.uk>
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: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/powerpc/include/asm/pgalloc.h b/arch/powerpc/include/asm/pgalloc.h
index 3360cad78acead9fc360d65498dda34b7fe0955e..3a971e2a8c73dfdc4205d4dd90c6a540a86688cf 100644 (file)
--- a/arch/powerpc/include/asm/pgalloc.h
+++ b/arch/powerpc/include/asm/pgalloc.h
@@ -45,6 +45,10 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t ptepage)
        pte_fragment_free((unsigned long *)ptepage, 0);
 }
 
+/* arch use pte_free_defer() implementation in arch/powerpc/mm/pgtable-frag.c */
+#define pte_free_defer pte_free_defer
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable);
+
 /*
  * Functions that deal with pagetables that could be at any level of
  * the table need to be passed an "index_size" so they know how to

diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
index 20652daa1d7e3ab154b1f2fcd1782b6901c81a01..0c6b681300256cb5c851b80d02bf01fb25748554 100644 (file)
--- a/arch/powerpc/mm/pgtable-frag.c
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -106,6 +106,15 @@ pte_t *pte_fragment_alloc(struct mm_struct *mm, int kernel)
        return __alloc_for_ptecache(mm, kernel);
 }
 
+static void pte_free_now(struct rcu_head *head)
+{
+       struct page *page;
+
+       page = container_of(head, struct page, rcu_head);
+       pgtable_pte_page_dtor(page);
+       __free_page(page);
+}
+
 void pte_fragment_free(unsigned long *table, int kernel)
 {
        struct page *page = virt_to_page(table);
@@ -115,8 +124,22 @@ void pte_fragment_free(unsigned long *table, int kernel)
 
        BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
        if (atomic_dec_and_test(&page->pt_frag_refcount)) {
-               if (!kernel)
-                       pgtable_pte_page_dtor(page);
-               __free_page(page);
+               if (kernel)
+                       __free_page(page);
+               else if (TestClearPageActive(page))
+                       call_rcu(&page->rcu_head, pte_free_now);
+               else
+                       pte_free_now(&page->rcu_head);
        }
 }
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
+{
+       struct page *page;
+
+       page = virt_to_page(pgtable);
+       SetPageActive(page);
+       pte_fragment_free((unsigned long *)pgtable, 0);
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */