From 253d553ba75ab26b3e9e2f70cbf6fbf0813f7e86 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 14 Dec 2009 17:58:44 -0800 Subject: swap_info: SWAP_HAS_CACHE cleanups Though swap_count() is useful, I'm finding that swap_has_cache() and encode_swapmap() obscure what happens in the swap_map entry, just at those points where I need to understand it. Remove them, and pass more usable "usage" values to scan_swap_map(), swap_entry_free() and __swap_duplicate(), instead of the SWAP_MAP and SWAP_CACHE enum. Signed-off-by: Hugh Dickins Reviewed-by: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 2 +- mm/swapfile.c | 155 +++++++++++++++++++++------------------------------ 2 files changed, 65 insertions(+), 92 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 109dfe794237..c9d8870892b8 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -154,7 +154,7 @@ enum { #define SWAP_MAP_MAX 0x7ffe #define SWAP_MAP_BAD 0x7fff #define SWAP_HAS_CACHE 0x8000 /* There is a swap cache of entry. */ -#define SWAP_COUNT_MASK (~SWAP_HAS_CACHE) + /* * The in-memory structure used to track swap areas. */ diff --git a/mm/swapfile.c b/mm/swapfile.c index fa5f10b9c28b..52497490a7ca 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -53,30 +53,9 @@ static struct swap_info_struct *swap_info[MAX_SWAPFILES]; static DEFINE_MUTEX(swapon_mutex); -/* For reference count accounting in swap_map */ -/* enum for swap_map[] handling. internal use only */ -enum { - SWAP_MAP = 0, /* ops for reference from swap users */ - SWAP_CACHE, /* ops for reference from swap cache */ -}; - static inline int swap_count(unsigned short ent) { - return ent & SWAP_COUNT_MASK; -} - -static inline bool swap_has_cache(unsigned short ent) -{ - return !!(ent & SWAP_HAS_CACHE); -} - -static inline unsigned short encode_swapmap(int count, bool has_cache) -{ - unsigned short ret = count; - - if (has_cache) - return SWAP_HAS_CACHE | ret; - return ret; + return ent & ~SWAP_HAS_CACHE; } /* returns 1 if swap entry is freed */ @@ -224,7 +203,7 @@ static int wait_for_discard(void *word) #define LATENCY_LIMIT 256 static inline unsigned long scan_swap_map(struct swap_info_struct *si, - int cache) + unsigned short usage) { unsigned long offset; unsigned long scan_base; @@ -355,10 +334,7 @@ checks: si->lowest_bit = si->max; si->highest_bit = 0; } - if (cache == SWAP_CACHE) /* at usual swap-out via vmscan.c */ - si->swap_map[offset] = encode_swapmap(0, true); - else /* at suspend */ - si->swap_map[offset] = encode_swapmap(1, false); + si->swap_map[offset] = usage; si->cluster_next = offset + 1; si->flags -= SWP_SCANNING; @@ -483,7 +459,7 @@ swp_entry_t get_swap_page(void) swap_list.next = next; /* This is called for allocating swap entry for cache */ - offset = scan_swap_map(si, SWAP_CACHE); + offset = scan_swap_map(si, SWAP_HAS_CACHE); if (offset) { spin_unlock(&swap_lock); return swp_entry(type, offset); @@ -508,7 +484,7 @@ swp_entry_t get_swap_page_of_type(int type) if (si && (si->flags & SWP_WRITEOK)) { nr_swap_pages--; /* This is called for allocating swap entry, not cache */ - offset = scan_swap_map(si, SWAP_MAP); + offset = scan_swap_map(si, 1); if (offset) { spin_unlock(&swap_lock); return swp_entry(type, offset); @@ -555,29 +531,31 @@ out: return NULL; } -static int swap_entry_free(struct swap_info_struct *p, - swp_entry_t ent, int cache) +static unsigned short swap_entry_free(struct swap_info_struct *p, + swp_entry_t entry, unsigned short usage) { - unsigned long offset = swp_offset(ent); - int count = swap_count(p->swap_map[offset]); - bool has_cache; + unsigned long offset = swp_offset(entry); + unsigned short count; + unsigned short has_cache; - has_cache = swap_has_cache(p->swap_map[offset]); + count = p->swap_map[offset]; + has_cache = count & SWAP_HAS_CACHE; + count &= ~SWAP_HAS_CACHE; - if (cache == SWAP_MAP) { /* dropping usage count of swap */ - if (count < SWAP_MAP_MAX) { - count--; - p->swap_map[offset] = encode_swapmap(count, has_cache); - } - } else { /* dropping swap cache flag */ + if (usage == SWAP_HAS_CACHE) { VM_BUG_ON(!has_cache); - p->swap_map[offset] = encode_swapmap(count, false); + has_cache = 0; + } else if (count < SWAP_MAP_MAX) + count--; + + if (!count) + mem_cgroup_uncharge_swap(entry); + + usage = count | has_cache; + p->swap_map[offset] = usage; - } - /* return code. */ - count = p->swap_map[offset]; /* free if no reference */ - if (!count) { + if (!usage) { if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) @@ -588,9 +566,8 @@ static int swap_entry_free(struct swap_info_struct *p, nr_swap_pages++; p->inuse_pages--; } - if (!swap_count(count)) - mem_cgroup_uncharge_swap(ent); - return count; + + return usage; } /* @@ -603,7 +580,7 @@ void swap_free(swp_entry_t entry) p = swap_info_get(entry); if (p) { - swap_entry_free(p, entry, SWAP_MAP); + swap_entry_free(p, entry, 1); spin_unlock(&swap_lock); } } @@ -614,19 +591,13 @@ void swap_free(swp_entry_t entry) void swapcache_free(swp_entry_t entry, struct page *page) { struct swap_info_struct *p; - int ret; + unsigned short count; p = swap_info_get(entry); if (p) { - ret = swap_entry_free(p, entry, SWAP_CACHE); - if (page) { - bool swapout; - if (ret) - swapout = true; /* the end of swap out */ - else - swapout = false; /* no more swap users! */ - mem_cgroup_uncharge_swapcache(page, entry, swapout); - } + count = swap_entry_free(p, entry, SWAP_HAS_CACHE); + if (page) + mem_cgroup_uncharge_swapcache(page, entry, count != 0); spin_unlock(&swap_lock); } } @@ -705,7 +676,7 @@ int free_swap_and_cache(swp_entry_t entry) p = swap_info_get(entry); if (p) { - if (swap_entry_free(p, entry, SWAP_MAP) == SWAP_HAS_CACHE) { + if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { page = find_get_page(&swapper_space, entry.val); if (page && !trylock_page(page)) { page_cache_release(page); @@ -1212,7 +1183,7 @@ static int try_to_unuse(unsigned int type) if (swap_count(*swap_map) == SWAP_MAP_MAX) { spin_lock(&swap_lock); - *swap_map = encode_swapmap(0, true); + *swap_map = SWAP_HAS_CACHE; spin_unlock(&swap_lock); reset_overflow = 1; } @@ -2111,16 +2082,16 @@ void si_swapinfo(struct sysinfo *val) * - swap-cache reference is requested but there is already one. -> EEXIST * - swap-cache reference is requested but the entry is not used. -> ENOENT */ -static int __swap_duplicate(swp_entry_t entry, bool cache) +static int __swap_duplicate(swp_entry_t entry, unsigned short usage) { struct swap_info_struct *p; unsigned long offset, type; - int result = -EINVAL; - int count; - bool has_cache; + unsigned short count; + unsigned short has_cache; + int err = -EINVAL; if (non_swap_entry(entry)) - return -EINVAL; + goto out; type = swp_type(entry); if (type >= nr_swapfiles) @@ -2129,54 +2100,56 @@ static int __swap_duplicate(swp_entry_t entry, bool cache) offset = swp_offset(entry); spin_lock(&swap_lock); - if (unlikely(offset >= p->max)) goto unlock_out; - count = swap_count(p->swap_map[offset]); - has_cache = swap_has_cache(p->swap_map[offset]); + count = p->swap_map[offset]; + has_cache = count & SWAP_HAS_CACHE; + count &= ~SWAP_HAS_CACHE; + err = 0; - if (cache == SWAP_CACHE) { /* called for swapcache/swapin-readahead */ + if (usage == SWAP_HAS_CACHE) { /* set SWAP_HAS_CACHE if there is no cache and entry is used */ - if (!has_cache && count) { - p->swap_map[offset] = encode_swapmap(count, true); - result = 0; - } else if (has_cache) /* someone added cache */ - result = -EEXIST; - else if (!count) /* no users */ - result = -ENOENT; + if (!has_cache && count) + has_cache = SWAP_HAS_CACHE; + else if (has_cache) /* someone else added cache */ + err = -EEXIST; + else /* no users remaining */ + err = -ENOENT; } else if (count || has_cache) { - if (count < SWAP_MAP_MAX - 1) { - p->swap_map[offset] = encode_swapmap(count + 1, - has_cache); - result = 0; - } else if (count <= SWAP_MAP_MAX) { + + if (count < SWAP_MAP_MAX - 1) + count++; + else if (count <= SWAP_MAP_MAX) { if (swap_overflow++ < 5) printk(KERN_WARNING "swap_dup: swap entry overflow\n"); - p->swap_map[offset] = encode_swapmap(SWAP_MAP_MAX, - has_cache); - result = 0; - } + count = SWAP_MAP_MAX; + } else + err = -EINVAL; } else - result = -ENOENT; /* unused swap entry */ + err = -ENOENT; /* unused swap entry */ + + p->swap_map[offset] = count | has_cache; + unlock_out: spin_unlock(&swap_lock); out: - return result; + return err; bad_file: printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); goto out; } + /* * increase reference count of swap entry by 1. */ void swap_duplicate(swp_entry_t entry) { - __swap_duplicate(entry, SWAP_MAP); + __swap_duplicate(entry, 1); } /* @@ -2189,7 +2162,7 @@ void swap_duplicate(swp_entry_t entry) */ int swapcache_prepare(swp_entry_t entry) { - return __swap_duplicate(entry, SWAP_CACHE); + return __swap_duplicate(entry, SWAP_HAS_CACHE); } /* -- cgit v1.2.3