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Subject: Re: [PATCH] mm/swap_slots: use conditional compilation for
 swap_slots.c
To: Randy Dunlap <rdunlap@infradead.org>, Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>
References: <c2a47015-0b5a-d0d9-8bc7-9984c049df20@infradead.org>
From: Tim Chen <tim.c.chen@linux.intel.com>
Message-ID: <1aa4baf5-7d56-84f9-e66d-476acaaec330@linux.intel.com>
Date: Tue, 30 Jan 2018 15:54:45 -0800
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On 01/30/2018 03:14 PM, Randy Dunlap wrote:
> From: Randy Dunlap <rdunlap@infradead.org>
> 
> For mm/swap_slots.c, use the traditional Linux method of conditional
> compilation and linking instead of always compiling it by using
> #ifdef CONFIG_SWAP and #endif for the entire source file (excluding
> header files).
> 
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Cc: Tim Chen <tim.c.chen@linux.intel.com>
> ---
>  mm/Makefile     |    4 ++--
>  mm/swap_slots.c |    4 ----
>  2 files changed, 2 insertions(+), 6 deletions(-)
> 
> Tim, is there some reason that this is done as it currently is?

Rearranging code the way you have proposed makes sense.
You can add my ack.

Thanks.

Tim

> 
> --- lnx-415.orig/mm/Makefile
> +++ lnx-415/mm/Makefile
> @@ -37,7 +37,7 @@ obj-y			:= filemap.o mempool.o oom_kill.
>  			   readahead.o swap.o truncate.o vmscan.o shmem.o \
>  			   util.o mmzone.o vmstat.o backing-dev.o \
>  			   mm_init.o mmu_context.o percpu.o slab_common.o \
> -			   compaction.o vmacache.o swap_slots.o \
> +			   compaction.o vmacache.o \
>  			   interval_tree.o list_lru.o workingset.o \
>  			   debug.o $(mmu-y)
>  
> @@ -55,7 +55,7 @@ ifdef CONFIG_MMU
>  endif
>  obj-$(CONFIG_HAVE_MEMBLOCK) += memblock.o
>  
> -obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o
> +obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o swap_slots.o
>  obj-$(CONFIG_FRONTSWAP)	+= frontswap.o
>  obj-$(CONFIG_ZSWAP)	+= zswap.o
>  obj-$(CONFIG_HAS_DMA)	+= dmapool.o
> --- lnx-415.orig/mm/swap_slots.c
> +++ lnx-415/mm/swap_slots.c
> @@ -34,8 +34,6 @@
>  #include <linux/mutex.h>
>  #include <linux/mm.h>
>  
> -#ifdef CONFIG_SWAP
> -
>  static DEFINE_PER_CPU(struct swap_slots_cache, swp_slots);
>  static bool	swap_slot_cache_active;
>  bool	swap_slot_cache_enabled;
> @@ -356,5 +354,3 @@ repeat:
>  
>  	return entry;
>  }
> -
> -#endif /* CONFIG_SWAP */
> 
>