The patch titled
Subject: mm: fix get_user_pages() vs device-dax pud mappings
has been added to the -mm tree. Its filename is
mm-fix-get_user_pages-vs-device-dax-pud-mappings.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-get_user_pages-vs-device-dax-pud-mappings.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-get_user_pages-vs-device-dax-pud-mappings.patch
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------------------------------------------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: mm: fix get_user_pages() vs device-dax pud mappings
A new unit test for the device-dax 1GB enabling currently fails with this
warning before hanging the test thread:
WARNING: CPU: 0 PID: 21 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0
percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic
[..]
CPU: 0 PID: 21 Comm: rcuos/1 Tainted: G O 4.10.0-rc7-next-20170207+ #944
[..]
Call Trace:
dump_stack+0x86/0xc3
__warn+0xcb/0xf0
warn_slowpath_fmt+0x5f/0x80
? rcu_nocb_kthread+0x27a/0x510
? dax_pmem_percpu_exit+0x50/0x50 [dax_pmem]
percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0
? percpu_ref_exit+0x60/0x60
rcu_nocb_kthread+0x339/0x510
? rcu_nocb_kthread+0x27a/0x510
kthread+0x101/0x140
The get_user_pages() path needs to arrange for references to be taken
against the dev_pagemap instance backing the pud mapping. Refactor the
existing __gup_device_huge_pmd() to also account for the pud case.
Link: http://lkml.kernel.org/r/148653181153.38226.9605457830505509385.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Nilesh Choudhury <nilesh.choudhury@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/gup.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff -puN arch/x86/mm/gup.c~mm-fix-get_user_pages-vs-device-dax-pud-mappings arch/x86/mm/gup.c
--- a/arch/x86/mm/gup.c~mm-fix-get_user_pages-vs-device-dax-pud-mappings
+++ a/arch/x86/mm/gup.c
@@ -154,14 +154,12 @@ static inline void get_head_page_multipl
SetPageReferenced(page);
}
-static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
+static int __gup_device_huge(unsigned long pfn, unsigned long addr,
unsigned long end, struct page **pages, int *nr)
{
int nr_start = *nr;
- unsigned long pfn = pmd_pfn(pmd);
struct dev_pagemap *pgmap = NULL;
- pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
do {
struct page *page = pfn_to_page(pfn);
@@ -180,6 +178,24 @@ static int __gup_device_huge_pmd(pmd_t p
return 1;
}
+static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
+ unsigned long end, struct page **pages, int *nr)
+{
+ unsigned long fault_pfn;
+
+ fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+ return __gup_device_huge(fault_pfn, addr, end, pages, nr);
+}
+
+static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
+ unsigned long end, struct page **pages, int *nr)
+{
+ unsigned long fault_pfn;
+
+ fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+ return __gup_device_huge(fault_pfn, addr, end, pages, nr);
+}
+
static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
@@ -251,9 +267,13 @@ static noinline int gup_huge_pud(pud_t p
if (!pte_allows_gup(pud_val(pud), write))
return 0;
+
+ VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
+ if (pud_devmap(pud))
+ return __gup_device_huge_pud(pud, addr, end, pages, nr);
+
/* hugepages are never "special" */
VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
- VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
refs = 0;
head = pud_page(pud);
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
mm-fix-type-width-of-section-to-from-pfn-conversion-macros.patch
mm-devm_memremap_pages-use-multi-order-radix-for-zone_device-lookups.patch
mm-introduce-struct-mem_section_usage-to-track-partial-population-of-a-section.patch
mm-introduce-common-definitions-for-the-size-and-mask-of-a-section.patch
mm-cleanup-sparse_init_one_section-return-value.patch
mm-track-active-portions-of-a-section-at-boot.patch
mm-fix-register_new_memory-zone-type-detection.patch
mm-convert-kmalloc_section_memmap-to-populate_section_memmap.patch
mm-prepare-for-hot-add-remove-of-sub-section-ranges.patch
mm-support-section-unaligned-zone_device-memory-ranges.patch
mm-support-section-unaligned-zone_device-memory-ranges-fix-2.patch
mm-enable-section-unaligned-devm_memremap_pages.patch
libnvdimm-pfn-dax-stop-padding-pmem-namespaces-to-section-alignment.patch
mm-fix-get_user_pages-vs-device-dax-pud-mappings.patch
--
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