Re: [PATCH] mm/hugetlb: Fix build failure with HUGETLB_PAGE but not HUGEBTLBFS

[Christophe Leroy <christophe.leroy@xxxxxx>]

Le 17/03/2020 à 09:25, Baoquan He a écrit :
> On 03/17/20 at 08:04am, Christophe Leroy wrote:
> > When CONFIG_HUGETLB_PAGE is set but not CONFIG_HUGETLBFS, the
> > following build failure is encoutered:
>
>  From the definition of HUGETLB_PAGE, isn't it relying on HUGETLBFS?
> I could misunderstand the def_bool, please correct me if I am wrong.

AFAIU, it means that HUGETLBFS rely on HUGETLB_PAGE, by default 
HUGETLB_PAGE is not selected when HUGETLBFS is not. But it is still 
possible for an arch to select HUGETLB_PAGE without selecting HUGETLBFS 
when it uses huge pages for other purpose than hugetlb file system.

Christophe

> config HUGETLB_PAGE
>          def_bool HUGETLBFS
>
> > In file included from arch/powerpc/mm/fault.c:33:0:
> > ./include/linux/hugetlb.h: In function 'hstate_inode':
> > ./include/linux/hugetlb.h:477:9: error: implicit declaration of function 'HUGETLBFS_SB' [-Werror=implicit-function-declaration]
> >    return HUGETLBFS_SB(i->i_sb)->hstate;
> >           ^
> > ./include/linux/hugetlb.h:477:30: error: invalid type argument of '->' (have 'int')
> >    return HUGETLBFS_SB(i->i_sb)->hstate;
> >                                ^
> >
> > Gate hstate_inode() with CONFIG_HUGETLBFS instead of CONFIG_HUGETLB_PAGE.
> >
> > Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> > Link: https://patchwork.ozlabs.org/patch/1255548/#2386036
> > Fixes: a137e1cc6d6e ("hugetlbfs: per mount huge page sizes")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> >   include/linux/hugetlb.h | 19 ++++++++-----------
> >   1 file changed, 8 insertions(+), 11 deletions(-)
> >
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 1e897e4168ac..dafb3d70ff81 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -390,7 +390,10 @@ static inline bool is_file_hugepages(struct file *file)
> >   	return is_file_shm_hugepages(file);
> >   }
> >   
> > -
> > +static inline struct hstate *hstate_inode(struct inode *i)
> > +{
> > +	return HUGETLBFS_SB(i->i_sb)->hstate;
> > +}
> >   #else /* !CONFIG_HUGETLBFS */
> >   
> >   #define is_file_hugepages(file)			false
> > @@ -402,6 +405,10 @@ hugetlb_file_setup(const char *name, size_t size, vm_flags_t acctflag,
> >   	return ERR_PTR(-ENOSYS);
> >   }
> >   
> > +static inline struct hstate *hstate_inode(struct inode *i)
> > +{
> > +	return NULL;
> > +}
> >   #endif /* !CONFIG_HUGETLBFS */
> >   
> >   #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
> > @@ -472,11 +479,6 @@ extern unsigned int default_hstate_idx;
> >   
> >   #define default_hstate (hstates[default_hstate_idx])
> >   
> > -static inline struct hstate *hstate_inode(struct inode *i)
> > -{
> > -	return HUGETLBFS_SB(i->i_sb)->hstate;
> > -}
> > -
> >   static inline struct hstate *hstate_file(struct file *f)
> >   {
> >   	return hstate_inode(file_inode(f));
> > @@ -729,11 +731,6 @@ static inline struct hstate *hstate_vma(struct vm_area_struct *vma)
> >   	return NULL;
> >   }
> >   
> > -static inline struct hstate *hstate_inode(struct inode *i)
> > -{
> > -	return NULL;
> > -}
> > -
> >   static inline struct hstate *page_hstate(struct page *page)
> >   {
> >   	return NULL;
> > --
> > 2.25.0