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Commit fe5266d5 authored by Huang Ying's avatar Huang Ying Committed by Linus Torvalds
Browse files

mm/swapfile.c: replace some #ifdef with IS_ENABLED() 

In mm/swapfile.c, THP (Transparent Huge Page) swap specific code is
enclosed by #ifdef CONFIG_THP_SWAP/#endif to avoid code dilating when
THP isn't enabled.  But #ifdef/#endif in .c file hurt the code
readability, so Dave suggested to use IS_ENABLED(CONFIG_THP_SWAP)
instead and let compiler to do the dirty job for us.  This has potential
to remove some duplicated code too.  From output of `size`,

		text	   data	    bss	    dec	    hex	filename
THP=y:         26269	   2076	    340	  28685	   700d	mm/swapfile.o
ifdef/endif:   24115	   2028	    340	  26483	   6773	mm/swapfile.o
IS_ENABLED:    24179	   2028	    340	  26547	   67b3	mm/swapfile.o

IS_ENABLED() based solution works quite well, almost as good as that of
#ifdef/#endif.  And from the diffstat, the removed lines are more than
added lines.

One #ifdef for split_swap_cluster() is kept.  Because it is a public
function with a stub implementation for CONFIG_THP_SWAP=n in swap.h.

Link: http://lkml.kernel.org/r/20180720071845.17920-3-ying.huang@intel.com


Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Suggested-and-acked-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarDaniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 59d98bf3

mm/swapfile.c

+20 −40
Original line number Diff line number Diff line
@@ -868,7 +868,6 @@ static int scan_swap_map_slots(struct swap_info_struct *si, 
	return n_ret;

}



#ifdef CONFIG_THP_SWAP

static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)

{

	unsigned long idx;
@@ -876,6 +875,15 @@ static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot) 
	unsigned long offset, i;

	unsigned char *map;



	/*

	 * Should not even be attempting cluster allocations when huge

	 * page swap is disabled.  Warn and fail the allocation.

	 */

	if (!IS_ENABLED(CONFIG_THP_SWAP)) {

		VM_WARN_ON_ONCE(1);

		return 0;

	}



	if (cluster_list_empty(&si->free_clusters))

		return 0;
@@ -906,13 +914,6 @@ static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx) 
	unlock_cluster(ci);

	swap_range_free(si, offset, SWAPFILE_CLUSTER);

}

#else

static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)

{

	VM_WARN_ON_ONCE(1);

	return 0;

}

#endif /* CONFIG_THP_SWAP */



static unsigned long scan_swap_map(struct swap_info_struct *si,

				   unsigned char usage)
@@ -1200,7 +1201,6 @@ static void swapcache_free(swp_entry_t entry) 
	}

}



#ifdef CONFIG_THP_SWAP

static void swapcache_free_cluster(swp_entry_t entry)

{

	unsigned long offset = swp_offset(entry);
@@ -1211,6 +1211,9 @@ static void swapcache_free_cluster(swp_entry_t entry) 
	unsigned int i, free_entries = 0;

	unsigned char val;



	if (!IS_ENABLED(CONFIG_THP_SWAP))

		return;



	si = _swap_info_get(entry);

	if (!si)

		return;
@@ -1246,6 +1249,7 @@ static void swapcache_free_cluster(swp_entry_t entry) 
	}

}



#ifdef CONFIG_THP_SWAP

int split_swap_cluster(swp_entry_t entry)

{

	struct swap_info_struct *si;
@@ -1260,11 +1264,7 @@ int split_swap_cluster(swp_entry_t entry) 
	unlock_cluster(ci);

	return 0;

}

#else

static inline void swapcache_free_cluster(swp_entry_t entry)

{

}

#endif /* CONFIG_THP_SWAP */

#endif



void put_swap_page(struct page *page, swp_entry_t entry)

{
@@ -1414,7 +1414,6 @@ int swp_swapcount(swp_entry_t entry) 
	return count;

}



#ifdef CONFIG_THP_SWAP

static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,

					 swp_entry_t entry)

{
@@ -1425,6 +1424,9 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si, 
	int i;

	bool ret = false;



	if (!IS_ENABLED(CONFIG_THP_SWAP))

		return swap_swapcount(si, entry) != 0;



	ci = lock_cluster_or_swap_info(si, offset);

	if (!ci || !cluster_is_huge(ci)) {

		if (map[roffset] != SWAP_HAS_CACHE)
@@ -1447,7 +1449,7 @@ static bool page_swapped(struct page *page) 
	swp_entry_t entry;

	struct swap_info_struct *si;



	if (likely(!PageTransCompound(page)))

	if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))

		return page_swapcount(page) != 0;



	page = compound_head(page);
@@ -1471,10 +1473,8 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount, 
	/* hugetlbfs shouldn't call it */

	VM_BUG_ON_PAGE(PageHuge(page), page);



	if (likely(!PageTransCompound(page))) {

		mapcount = atomic_read(&page->_mapcount) + 1;

		if (total_mapcount)

			*total_mapcount = mapcount;

	if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {

		mapcount = page_trans_huge_mapcount(page, total_mapcount);

		if (PageSwapCache(page))

			swapcount = page_swapcount(page);

		if (total_swapcount)
@@ -1521,26 +1521,6 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount, 


	return map_swapcount;

}

#else

#define swap_page_trans_huge_swapped(si, entry)	swap_swapcount(si, entry)

#define page_swapped(page)			(page_swapcount(page) != 0)



static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,

					 int *total_swapcount)

{

	int mapcount, swapcount = 0;



	/* hugetlbfs shouldn't call it */

	VM_BUG_ON_PAGE(PageHuge(page), page);



	mapcount = page_trans_huge_mapcount(page, total_mapcount);

	if (PageSwapCache(page))

		swapcount = page_swapcount(page);

	if (total_swapcount)

		*total_swapcount = swapcount;

	return mapcount + swapcount;

}

#endif



/*

 * We can write to an anon page without COW if there are no other references