Commit cb4b86ba authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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mm: add swap cache interface for swap reference 



In a following patch, the usage of swap cache is recorded into swap_map.
This patch is for necessary interface changes to do that.

2 interfaces:

  - swapcache_prepare()
  - swapcache_free()

are added for allocating/freeing refcnt from swap-cache to existing swap
entries.  But implementation itself is not changed under this patch.  At
adding swapcache_free(), memcg's hook code is moved under
swapcache_free().  This is better than using scattered hooks.

Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: default avatarBalbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 68377659

include/linux/swap.h

+7 −0
Original line number Diff line number Diff line
@@ -282,8 +282,10 @@ extern void si_swapinfo(struct sysinfo *); 
extern swp_entry_t get_swap_page(void);

extern swp_entry_t get_swap_page_of_type(int);

extern int swap_duplicate(swp_entry_t);

extern int swapcache_prepare(swp_entry_t);

extern int valid_swaphandles(swp_entry_t, unsigned long *);

extern void swap_free(swp_entry_t);

extern void swapcache_free(swp_entry_t, struct page *page);

extern int free_swap_and_cache(swp_entry_t);

extern int swap_type_of(dev_t, sector_t, struct block_device **);

extern unsigned int count_swap_pages(int, int);
@@ -352,11 +354,16 @@ static inline void show_swap_cache_info(void) 


#define free_swap_and_cache(swp)	is_migration_entry(swp)

#define swap_duplicate(swp)		is_migration_entry(swp)

#define swapcache_prepare(swp)		is_migration_entry(swp)



static inline void swap_free(swp_entry_t swp)

{

}



static inline void swapcache_free(swp_entry_t swp, struct page *page)

{

}



static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,

			struct vm_area_struct *vma, unsigned long addr)

{

mm/shmem.c

+1 −1
Original line number Diff line number Diff line
@@ -1097,7 +1097,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
	shmem_swp_unmap(entry);

unlock:

	spin_unlock(&info->lock);

	swap_free(swap);

	swapcache_free(swap, NULL);

redirty:

	set_page_dirty(page);

	if (wbc->for_reclaim)

mm/swap_state.c

+5 −6
Original line number Diff line number Diff line
@@ -162,11 +162,11 @@ int add_to_swap(struct page *page) 
			return 1;

		case -EEXIST:

			/* Raced with "speculative" read_swap_cache_async */

			swap_free(entry);

			swapcache_free(entry, NULL);

			continue;

		default:

			/* -ENOMEM radix-tree allocation failure */

			swap_free(entry);

			swapcache_free(entry, NULL);

			return 0;

		}

	}
@@ -188,8 +188,7 @@ void delete_from_swap_cache(struct page *page) 
	__delete_from_swap_cache(page);

	spin_unlock_irq(&swapper_space.tree_lock);



	mem_cgroup_uncharge_swapcache(page, entry);

	swap_free(entry);

	swapcache_free(entry, page);

	page_cache_release(page);

}
@@ -293,7 +292,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
		/*

		 * Swap entry may have been freed since our caller observed it.

		 */

		if (!swap_duplicate(entry))

		if (!swapcache_prepare(entry))

			break;



		/*
@@ -317,7 +316,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
		}

		ClearPageSwapBacked(new_page);

		__clear_page_locked(new_page);

		swap_free(entry);

		swapcache_free(entry, NULL);

	} while (err != -ENOMEM);



	if (new_page)

mm/swapfile.c

+19 −0
Original line number Diff line number Diff line
@@ -509,6 +509,16 @@ void swap_free(swp_entry_t entry) 
	}

}



/*

 * Called after dropping swapcache to decrease refcnt to swap entries.

 */

void swapcache_free(swp_entry_t entry, struct page *page)

{

	if (page)

		mem_cgroup_uncharge_swapcache(page, entry);

	return swap_free(entry);

}



/*

 * How many references to page are currently swapped out?

 */
@@ -1979,6 +1989,15 @@ bad_file: 
	goto out;

}



/*

 * Called when allocating swap cache for exising swap entry,

 */

int swapcache_prepare(swp_entry_t entry)

{

	return swap_duplicate(entry);

}





struct swap_info_struct *

get_swap_info_struct(unsigned type)

{

mm/vmscan.c

+1 −2
Original line number Diff line number Diff line
@@ -470,8 +470,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page) 
		swp_entry_t swap = { .val = page_private(page) };

		__delete_from_swap_cache(page);

		spin_unlock_irq(&mapping->tree_lock);

		mem_cgroup_uncharge_swapcache(page, swap);

		swap_free(swap);

		swapcache_free(swap, page);

	} else {

		__remove_from_page_cache(page);

		spin_unlock_irq(&mapping->tree_lock);

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