mm/hugepages: fix "orig_pud" set but not used
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Message ID 20190301004903.89514-1-cai@lca.pw
State New
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Series
  • mm/hugepages: fix "orig_pud" set but not used
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Commit Message

Qian Cai March 1, 2019, 12:49 a.m. UTC
The commit a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent
hugepages") introduced pudp_huge_get_and_clear_full() but no one uses
its return code, so just make it void.

mm/huge_memory.c: In function 'zap_huge_pud':
mm/huge_memory.c:1982:8: warning: variable 'orig_pud' set but not used
[-Wunused-but-set-variable]
  pud_t orig_pud;
        ^~~~~~~~

Signed-off-by: Qian Cai <cai@lca.pw>
---
 include/asm-generic/pgtable.h | 8 ++++----
 mm/huge_memory.c              | 4 +---
 2 files changed, 5 insertions(+), 7 deletions(-)

Comments

Andrew Morton March 1, 2019, 9:09 p.m. UTC | #1
On Thu, 28 Feb 2019 19:49:03 -0500 Qian Cai <cai@lca.pw> wrote:

> The commit a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent
> hugepages") introduced pudp_huge_get_and_clear_full() but no one uses
> its return code, so just make it void.
> 
> mm/huge_memory.c: In function 'zap_huge_pud':
> mm/huge_memory.c:1982:8: warning: variable 'orig_pud' set but not used
> [-Wunused-but-set-variable]
>   pud_t orig_pud;
>         ^~~~~~~~
> 
> ...
>
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -167,11 +167,11 @@ static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
>  #endif
>  
>  #ifndef __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR_FULL
> -static inline pud_t pudp_huge_get_and_clear_full(struct mm_struct *mm,
> -					    unsigned long address, pud_t *pudp,
> -					    int full)
> +static inline void pudp_huge_get_and_clear_full(struct mm_struct *mm,
> +						unsigned long address,
> +						pud_t *pudp, int full)
>  {
> -	return pudp_huge_get_and_clear(mm, address, pudp);
> +	pudp_huge_get_and_clear(mm, address, pudp);
>  }

Not sure this is a good change.  Future callers might want that return
value.

> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1979,7 +1979,6 @@ spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
>  int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  		 pud_t *pud, unsigned long addr)
>  {
> -	pud_t orig_pud;
>  	spinlock_t *ptl;
>  
>  	ptl = __pud_trans_huge_lock(pud, vma);
> @@ -1991,8 +1990,7 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  	 * pgtable_trans_huge_withdraw after finishing pudp related
>  	 * operations.
>  	 */
> -	orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
> -			tlb->fullmm);
> +	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);

In fact this code perhaps should be passing orig_pud into
pudp_huge_get_and_clear_full().  That could depend on what future
per-arch implementations of pudp_huge_get_and_clear_full() choose to
do.

Anyway, I'll await Matthew's feedback.
Matthew Wilcox March 1, 2019, 9:44 p.m. UTC | #2
On Fri, Mar 01, 2019 at 01:09:51PM -0800, Andrew Morton wrote:
> On Thu, 28 Feb 2019 19:49:03 -0500 Qian Cai <cai@lca.pw> wrote:
> 
> > The commit a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent
> > hugepages") introduced pudp_huge_get_and_clear_full() but no one uses
> > its return code, so just make it void.
> > 
> > mm/huge_memory.c: In function 'zap_huge_pud':
> > mm/huge_memory.c:1982:8: warning: variable 'orig_pud' set but not used
> > [-Wunused-but-set-variable]
> >   pud_t orig_pud;
> >         ^~~~~~~~
> > 
> > ...
> >
> > --- a/include/asm-generic/pgtable.h
> > +++ b/include/asm-generic/pgtable.h
> > @@ -167,11 +167,11 @@ static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
> >  #endif
> >  
> >  #ifndef __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR_FULL
> > -static inline pud_t pudp_huge_get_and_clear_full(struct mm_struct *mm,
> > -					    unsigned long address, pud_t *pudp,
> > -					    int full)
> > +static inline void pudp_huge_get_and_clear_full(struct mm_struct *mm,
> > +						unsigned long address,
> > +						pud_t *pudp, int full)
> >  {
> > -	return pudp_huge_get_and_clear(mm, address, pudp);
> > +	pudp_huge_get_and_clear(mm, address, pudp);
> >  }
> 
> Not sure this is a good change.  Future callers might want that return
> value.
> 
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -1979,7 +1979,6 @@ spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
> >  int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
> >  		 pud_t *pud, unsigned long addr)
> >  {
> > -	pud_t orig_pud;
> >  	spinlock_t *ptl;
> >  
> >  	ptl = __pud_trans_huge_lock(pud, vma);
> > @@ -1991,8 +1990,7 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
> >  	 * pgtable_trans_huge_withdraw after finishing pudp related
> >  	 * operations.
> >  	 */
> > -	orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
> > -			tlb->fullmm);
> > +	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
> 
> In fact this code perhaps should be passing orig_pud into
> pudp_huge_get_and_clear_full().  That could depend on what future
> per-arch implementations of pudp_huge_get_and_clear_full() choose to
> do.
> 
> Anyway, I'll await Matthew's feedback.

I'm not sure it's wise to diverge from pmdp_huge_get_and_clear_full()
which does return the orig_pud.  I agree we don't currently use it,
so maybe we should just change zap_huge_pud() to not assign the return
value from pudp_huge_get_and_clear_full()?

Patch
diff mbox series

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 05e61e6c843f..17b789557afe 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -167,11 +167,11 @@  static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
 #endif
 
 #ifndef __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR_FULL
-static inline pud_t pudp_huge_get_and_clear_full(struct mm_struct *mm,
-					    unsigned long address, pud_t *pudp,
-					    int full)
+static inline void pudp_huge_get_and_clear_full(struct mm_struct *mm,
+						unsigned long address,
+						pud_t *pudp, int full)
 {
-	return pudp_huge_get_and_clear(mm, address, pudp);
+	pudp_huge_get_and_clear(mm, address, pudp);
 }
 #endif
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index faf357eaf0ce..9f57a1173e6a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1979,7 +1979,6 @@  spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		 pud_t *pud, unsigned long addr)
 {
-	pud_t orig_pud;
 	spinlock_t *ptl;
 
 	ptl = __pud_trans_huge_lock(pud, vma);
@@ -1991,8 +1990,7 @@  int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 * pgtable_trans_huge_withdraw after finishing pudp related
 	 * operations.
 	 */
-	orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
-			tlb->fullmm);
+	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
 	tlb_remove_pud_tlb_entry(tlb, pud, addr);
 	if (vma_is_dax(vma)) {
 		spin_unlock(ptl);