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parisc: mm: don't count preallocated pmds

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The patch dc6c9a35b6 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>
This commit is contained in:
Mikulas Patocka 2015-03-18 13:42:38 -04:00 committed by Helge Deller
parent 47514da3ac
commit 0e0da48dee
1 changed files with 7 additions and 2 deletions
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9
arch/parisc/include/asm/pgalloc.h
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@ -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);