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mm/thp: split out pmd collapse flush into separate functions 

Architectures like ppc64 [1] need to do special things while clearing pmd
before a collapse.  For them this operation is largely different from a
normal hugepage pte clear.  Hence add a separate function to clear pmd
before collapse.  After this patch pmdp_* functions operate only on
hugepage pte, and not on regular pmd_t values pointing to page table.

[1] ppc64 needs to invalidate all the normal page pte mappings we already
have inserted in the hardware hash page table.  But before doing that we
need to make sure there are no parallel hash page table insert going on.
So we need to do a kick_all_cpus_sync() before flushing the older hash
table entries.  By moving this to a separate function we capture these
details and mention how it is different from a hugepage pte clear.

This patch is a cleanup and only does code movement for clarity.  There
should not be any change in functionality.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aneesh Kumar K.V 2015-06-24 16:57:39 -07:00 committed by Linus Torvalds
parent 97f0b13452
commit 15a25b2ead
4 changed files with 67 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/include/asm/pgtable-ppc64.h
View File

@ -592,6 +592,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
extern void pmdp_splitting_flush(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
#define pmdp_collapse_flush pmdp_collapse_flush
#define __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable);

18
arch/powerpc/mm/pgtable_64.c
View File

@ -560,12 +560,19 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
if (pmd_trans_huge(*pmdp)) {
VM_BUG_ON(!pmd_trans_huge(*pmdp));
pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
} else {
/*
* khugepaged calls this for normal pmd
*/
return pmd;
}
pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
VM_BUG_ON(pmd_trans_huge(*pmdp));
pmd = *pmdp;
pmd_clear(pmdp);
/*
@ -594,7 +601,6 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
* the old content.
*/
flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
}
return pmd;
}

21
include/asm-generic/pgtable.h
View File

@ -189,6 +189,27 @@ extern void pmdp_splitting_flush(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);
#endif
#ifndef pmdp_collapse_flush
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmdp)
{
return pmdp_clear_flush(vma, address, pmdp);
}
#define pmdp_collapse_flush pmdp_collapse_flush
#else
static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmdp)
{
BUILD_BUG();
return *pmdp;
}
#define pmdp_collapse_flush pmdp_collapse_flush
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif
#ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable);

2
mm/huge_memory.c
View File

@ -2499,7 +2499,7 @@ static void collapse_huge_page(struct mm_struct *mm,
* huge and small TLB entries for the same virtual address
* to avoid the risk of CPU bugs in that area.
*/
_pmd = pmdp_clear_flush(vma, address, pmd);
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);