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authorDan Williams <dan.j.williams@intel.com>2017-02-24 14:57:12 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:54 -0800
commit220ced1676c490c3192dd9bc1a06be86dee88a56 (patch)
tree8b42482effe559b2a24455eb5c13efa5ee4547ed /arch/x86
parentc791ace1e747371658237f0d30234fef56c39669 (diff)
downloadlinux-220ced1676c490c3192dd9bc1a06be86dee88a56.tar.bz2
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@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/mm/gup.c28
1 files changed, 24 insertions, 4 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 0d4fb3ebbbac..99c7805a9693 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -154,14 +154,12 @@ static inline void get_head_page_multiple(struct page *page, int nr)
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 pmd, unsigned long addr,
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 pud, unsigned long addr,
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);