On Tue, 10 Aug 2021, Feng Tang wrote: > On Mon, Aug 09, 2021 at 03:19:32PM +0200, Michal Hocko wrote: > [snip] > > > > Do you think you can provide same helpers for other policies as well? > > > > Maybe we can get rid of some other ifdefery as well. > > > > > > Sure. I can make separate patch(es) for that. > > > > > > And you mean helper like mpol_is_bind/default/local/preferred? > > > > > > I just run 'git-grep MPOL', and for places using "mode == MPOL_XXX", > > > mostly they are in mempolicy.[ch], the only another place is in > > > shmem.c, do we need to create all the helpers for it and the > > > potential future users? > > > > I would just go with those instances which need to ifdef for NUMA. > > Thanks! > > Yes, following is a patch to remove one CONFIG_NUMA check, though > an bolder idea to extend the patch by removing the CONFIG_TMPFS > check in the same line. > > Thanks, > Feng > > ---------8<--------------------------------- > > From 1a5858721ac8ce99c27c13d310bba2983dc73d97 Mon Sep 17 00:00:00 2001 > From: Feng Tang <feng.tang@xxxxxxxxx> > Date: Tue, 10 Aug 2021 17:00:59 +0800 > Subject: [PATCH] mm: shmem: avoid open coded check for mempolicy's mode > > Add a mempolicy helper to do the check, which can also remove > a CONFIG_NUMA option check. > > Suggested-by: Michal Hocko <mhocko@xxxxxxxx> > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> No thanks: this is not an improvement. The "#if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)" is there to eliminate dead code that would not be automatically eliminated by the optimizer: it's not there just to avoid MPOL_DEFAULT, and it's there to cover shmem_get_sbmpol() along with shmem_show_mpol(). I know we tend to avoid #ifdefs in .c files, and that's good; and I know you could find other code in mm/shmem.c which might also be #ifdef'ed to eliminate other dead code in other configs; but unless there's a new drive to purge our .c source of all #ifdefs, please just leave this as is. Thanks, Hugh > --- > include/linux/mempolicy.h | 14 ++++++++++++++ > mm/shmem.c | 8 ++++---- > 2 files changed, 18 insertions(+), 4 deletions(-) > > diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h > index 60d5e6c3340c..8fc518ad4f3c 100644 > --- a/include/linux/mempolicy.h > +++ b/include/linux/mempolicy.h > @@ -192,6 +192,10 @@ static inline bool mpol_is_preferred_many(struct mempolicy *pol) > return (pol->mode == MPOL_PREFERRED_MANY); > } > > +static inline bool mpol_is_default(struct mempolicy *pol) > +{ > + return (pol->mode == MPOL_DEFAULT); > +} > > #else > > @@ -287,6 +291,10 @@ static inline int mpol_parse_str(char *str, struct mempolicy **mpol) > } > #endif > > +static inline void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol) > +{ > +} > + > static inline int mpol_misplaced(struct page *page, struct vm_area_struct *vma, > unsigned long address) > { > @@ -309,5 +317,11 @@ static inline bool mpol_is_preferred_many(struct mempolicy *pol) > return false; > } > > +static inline bool mpol_is_default(struct mempolicy *pol) > +{ > + return false; > +} > + > + > #endif /* CONFIG_NUMA */ > #endif > diff --git a/mm/shmem.c b/mm/shmem.c > index 96f05f6af8bb..26b195209ef7 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1437,12 +1437,12 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > return 0; > } > > -#if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS) > +#ifdef CONFIG_TMPFS > static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) > { > char buffer[64]; > > - if (!mpol || mpol->mode == MPOL_DEFAULT) > + if (!mpol || mpol_is_default(mpol)) > return; /* show nothing */ > > mpol_to_str(buffer, sizeof(buffer), mpol); > @@ -1461,7 +1461,7 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) > } > return mpol; > } > -#else /* !CONFIG_NUMA || !CONFIG_TMPFS */ > +#else /* !CONFIG_TMPFS */ > static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) > { > } > @@ -1469,7 +1469,7 @@ static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) > { > return NULL; > } > -#endif /* CONFIG_NUMA && CONFIG_TMPFS */ > +#endif /* CONFIG_TMPFS */ > #ifndef CONFIG_NUMA > #define vm_policy vm_private_data > #endif > -- > 2.14.1