From 0e0da48dee8dfbcc0df4b8e2ff4efc7a2c89ba6b Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 18 Mar 2015 13:42:38 -0400
Subject: [PATCH] parisc: mm: don't count preallocated pmds
The patch dc6c9a35b66b520cf67e05d8ca60ebecad3b0479 that counts pmds
allocated for a process introduced a bug on 64-bit PA-RISC kernels.
The PA-RISC architecture preallocates one pmd with each pgd. This
preallocated pmd can never be freed - pmd_free does nothing when it is
called with this pmd. When the kernel attempts to free this preallocated
pmd, it decreases the count of allocated pmds. The result is that the
counter underflows and this error is reported.
This patch fixes the bug by artifically incrementing the counter in
pmd_free when the kernel tries to free the preallocated pmd.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Helge Deller <deller@gmx.de>
---
arch/parisc/include/asm/pgalloc.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
index f213f5b4c4239..63e9ecae13103 100644
--- a/arch/parisc/include/asm/pgalloc.h
+++ b/arch/parisc/include/asm/pgalloc.h
@@ -74,8 +74,13 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
{
#ifdef CONFIG_64BIT
if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
- /* This is the permanent pmd attached to the pgd;
- * cannot free it */
+ /*
+ * This is the permanent pmd attached to the pgd;
+ * cannot free it.
+ * Increment the counter to compensate for the decrement
+ * done by generic mm code.
+ */
+ mm_inc_nr_pmds(mm);
return;
#endif
free_pages((unsigned long)pmd, PMD_ORDER);
--
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