swap: add per-partition lock for swapfile
Shaohua Li [Sat, 23 Feb 2013 00:34:38 +0000 (16:34 -0800)]
swap_lock is heavily contended when I test swap to 3 fast SSD (even
slightly slower than swap to 2 such SSD).  The main contention comes
from swap_info_get().  This patch tries to fix the gap with adding a new
per-partition lock.

Global data like nr_swapfiles, total_swap_pages, least_priority and
swap_list are still protected by swap_lock.

nr_swap_pages is an atomic now, it can be changed without swap_lock.  In
theory, it's possible get_swap_page() finds no swap pages but actually
there are free swap pages.  But sounds not a big problem.

Accessing partition specific data (like scan_swap_map and so on) is only
protected by swap_info_struct.lock.

Changing swap_info_struct.flags need hold swap_lock and
swap_info_struct.lock, because scan_scan_map() will check it.  read the
flags is ok with either the locks hold.

If both swap_lock and swap_info_struct.lock must be hold, we always hold
the former first to avoid deadlock.

swap_entry_free() can change swap_list.  To delete that code, we add a
new highest_priority_index.  Whenever get_swap_page() is called, we
check it.  If it's valid, we use it.

It's a pity get_swap_page() still holds swap_lock().  But in practice,
swap_lock() isn't heavily contended in my test with this patch (or I can
say there are other much more heavier bottlenecks like TLB flush).  And
BTW, looks get_swap_page() doesn't really need the lock.  We never free
swap_info[] and we check SWAP_WRITEOK flag.  The only risk without the
lock is we could swapout to some low priority swap, but we can quickly
recover after several rounds of swap, so sounds not a big deal to me.
But I'd prefer to fix this if it's a real problem.

"swap: make each swap partition have one address_space" improved the
swapout speed from 1.7G/s to 2G/s.  This patch further improves the
speed to 2.3G/s, so around 15% improvement.  It's a multi-process test,
so TLB flush isn't the biggest bottleneck before the patches.

[arnd@arndb.de: fix it for nommu]
[hughd@google.com: add missing unlock]
[minchan@kernel.org: get rid of lockdep whinge on sys_swapon]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/sparc/mm/init_32.c
arch/tile/mm/pgtable.c
include/linux/swap.h
mm/mmap.c
mm/nommu.c
mm/swap_state.c
mm/swapfile.c
mm/vmscan.c

index dde85ef..48e0c03 100644 (file)
@@ -57,7 +57,7 @@ void show_mem(unsigned int filter)
        printk("Mem-info:\n");
        show_free_areas(filter);
        printk("Free swap:       %6ldkB\n",
-              nr_swap_pages << (PAGE_SHIFT-10));
+              get_nr_swap_pages() << (PAGE_SHIFT-10));
        printk("%ld pages of RAM\n", totalram_pages);
        printk("%ld free pages\n", nr_free_pages());
 }
index de0de0c..b3b4972 100644 (file)
@@ -61,7 +61,7 @@ void show_mem(unsigned int filter)
               global_page_state(NR_PAGETABLE),
               global_page_state(NR_BOUNCE),
               global_page_state(NR_FILE_PAGES),
-              nr_swap_pages);
+              get_nr_swap_pages());
 
        for_each_zone(zone) {
                unsigned long flags, order, total = 0, largest_order = -1;
index 235c039..a3e22d3 100644 (file)
@@ -202,6 +202,18 @@ struct swap_info_struct {
        unsigned long *frontswap_map;   /* frontswap in-use, one bit per page */
        atomic_t frontswap_pages;       /* frontswap pages in-use counter */
 #endif
+       spinlock_t lock;                /*
+                                        * protect map scan related fields like
+                                        * swap_map, lowest_bit, highest_bit,
+                                        * inuse_pages, cluster_next,
+                                        * cluster_nr, lowest_alloc and
+                                        * highest_alloc. other fields are only
+                                        * changed at swapon/swapoff, so are
+                                        * protected by swap_lock. changing
+                                        * flags need hold this lock and
+                                        * swap_lock. If both locks need hold,
+                                        * hold swap_lock first.
+                                        */
 };
 
 struct swap_list_t {
@@ -209,9 +221,6 @@ struct swap_list_t {
        int next;       /* swapfile to be used next */
 };
 
-/* Swap 50% full? Release swapcache more aggressively.. */
-#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
-
 /* linux/mm/page_alloc.c */
 extern unsigned long totalram_pages;
 extern unsigned long totalreserve_pages;
@@ -347,8 +356,20 @@ extern struct page *swapin_readahead(swp_entry_t, gfp_t,
                        struct vm_area_struct *vma, unsigned long addr);
 
 /* linux/mm/swapfile.c */
-extern long nr_swap_pages;
+extern atomic_long_t nr_swap_pages;
 extern long total_swap_pages;
+
+/* Swap 50% full? Release swapcache more aggressively.. */
+static inline bool vm_swap_full(void)
+{
+       return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
+}
+
+static inline long get_nr_swap_pages(void)
+{
+       return atomic_long_read(&nr_swap_pages);
+}
+
 extern void si_swapinfo(struct sysinfo *);
 extern swp_entry_t get_swap_page(void);
 extern swp_entry_t get_swap_page_of_type(int);
@@ -381,9 +402,10 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 
 #else /* CONFIG_SWAP */
 
-#define nr_swap_pages                          0L
+#define get_nr_swap_pages()                    0L
 #define total_swap_pages                       0L
 #define total_swapcache_pages()                        0UL
+#define vm_swap_full()                         0
 
 #define si_swapinfo(val) \
        do { (val)->freeswap = (val)->totalswap = 0; } while (0)
index 44bb4d8..28416f6 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -144,7 +144,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
                 */
                free -= global_page_state(NR_SHMEM);
 
-               free += nr_swap_pages;
+               free += get_nr_swap_pages();
 
                /*
                 * Any slabs which are created with the
index 18c1b93..87854a5 100644 (file)
@@ -1907,7 +1907,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
                 */
                free -= global_page_state(NR_SHMEM);
 
-               free += nr_swap_pages;
+               free += get_nr_swap_pages();
 
                /*
                 * Any slabs which are created with the
index 8d6644c..7efcf15 100644 (file)
@@ -69,7 +69,8 @@ void show_swap_cache_info(void)
        printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
                swap_cache_info.add_total, swap_cache_info.del_total,
                swap_cache_info.find_success, swap_cache_info.find_total);
-       printk("Free swap  = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
+       printk("Free swap  = %ldkB\n",
+               get_nr_swap_pages() << (PAGE_SHIFT - 10));
        printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
 }
 
index e51864e..9b51266 100644 (file)
@@ -47,9 +47,11 @@ static sector_t map_swap_entry(swp_entry_t, struct block_device**);
 
 DEFINE_SPINLOCK(swap_lock);
 static unsigned int nr_swapfiles;
-long nr_swap_pages;
+atomic_long_t nr_swap_pages;
+/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
 long total_swap_pages;
 static int least_priority;
+static atomic_t highest_priority_index = ATOMIC_INIT(-1);
 
 static const char Bad_file[] = "Bad swap file entry ";
 static const char Unused_file[] = "Unused swap file entry ";
@@ -223,7 +225,7 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
                        si->lowest_alloc = si->max;
                        si->highest_alloc = 0;
                }
-               spin_unlock(&swap_lock);
+               spin_unlock(&si->lock);
 
                /*
                 * If seek is expensive, start searching for new cluster from
@@ -242,7 +244,7 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
                        if (si->swap_map[offset])
                                last_in_cluster = offset + SWAPFILE_CLUSTER;
                        else if (offset == last_in_cluster) {
-                               spin_lock(&swap_lock);
+                               spin_lock(&si->lock);
                                offset -= SWAPFILE_CLUSTER - 1;
                                si->cluster_next = offset;
                                si->cluster_nr = SWAPFILE_CLUSTER - 1;
@@ -263,7 +265,7 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
                        if (si->swap_map[offset])
                                last_in_cluster = offset + SWAPFILE_CLUSTER;
                        else if (offset == last_in_cluster) {
-                               spin_lock(&swap_lock);
+                               spin_lock(&si->lock);
                                offset -= SWAPFILE_CLUSTER - 1;
                                si->cluster_next = offset;
                                si->cluster_nr = SWAPFILE_CLUSTER - 1;
@@ -277,7 +279,7 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
                }
 
                offset = scan_base;
-               spin_lock(&swap_lock);
+               spin_lock(&si->lock);
                si->cluster_nr = SWAPFILE_CLUSTER - 1;
                si->lowest_alloc = 0;
        }
@@ -293,9 +295,9 @@ checks:
        /* reuse swap entry of cache-only swap if not busy. */
        if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
                int swap_was_freed;
-               spin_unlock(&swap_lock);
+               spin_unlock(&si->lock);
                swap_was_freed = __try_to_reclaim_swap(si, offset);
-               spin_lock(&swap_lock);
+               spin_lock(&si->lock);
                /* entry was freed successfully, try to use this again */
                if (swap_was_freed)
                        goto checks;
@@ -335,13 +337,13 @@ checks:
                            si->lowest_alloc <= last_in_cluster)
                                last_in_cluster = si->lowest_alloc - 1;
                        si->flags |= SWP_DISCARDING;
-                       spin_unlock(&swap_lock);
+                       spin_unlock(&si->lock);
 
                        if (offset < last_in_cluster)
                                discard_swap_cluster(si, offset,
                                        last_in_cluster - offset + 1);
 
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                        si->lowest_alloc = 0;
                        si->flags &= ~SWP_DISCARDING;
 
@@ -355,10 +357,10 @@ checks:
                         * could defer that delay until swap_writepage,
                         * but it's easier to keep this self-contained.
                         */
-                       spin_unlock(&swap_lock);
+                       spin_unlock(&si->lock);
                        wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
                                wait_for_discard, TASK_UNINTERRUPTIBLE);
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                } else {
                        /*
                         * Note pages allocated by racing tasks while
@@ -374,14 +376,14 @@ checks:
        return offset;
 
 scan:
-       spin_unlock(&swap_lock);
+       spin_unlock(&si->lock);
        while (++offset <= si->highest_bit) {
                if (!si->swap_map[offset]) {
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                        goto checks;
                }
                if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                        goto checks;
                }
                if (unlikely(--latency_ration < 0)) {
@@ -392,11 +394,11 @@ scan:
        offset = si->lowest_bit;
        while (++offset < scan_base) {
                if (!si->swap_map[offset]) {
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                        goto checks;
                }
                if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
-                       spin_lock(&swap_lock);
+                       spin_lock(&si->lock);
                        goto checks;
                }
                if (unlikely(--latency_ration < 0)) {
@@ -404,7 +406,7 @@ scan:
                        latency_ration = LATENCY_LIMIT;
                }
        }
-       spin_lock(&swap_lock);
+       spin_lock(&si->lock);
 
 no_page:
        si->flags -= SWP_SCANNING;
@@ -417,13 +419,34 @@ swp_entry_t get_swap_page(void)
        pgoff_t offset;
        int type, next;
        int wrapped = 0;
+       int hp_index;
 
        spin_lock(&swap_lock);
-       if (nr_swap_pages <= 0)
+       if (atomic_long_read(&nr_swap_pages) <= 0)
                goto noswap;
-       nr_swap_pages--;
+       atomic_long_dec(&nr_swap_pages);
 
        for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
+               hp_index = atomic_xchg(&highest_priority_index, -1);
+               /*
+                * highest_priority_index records current highest priority swap
+                * type which just frees swap entries. If its priority is
+                * higher than that of swap_list.next swap type, we use it.  It
+                * isn't protected by swap_lock, so it can be an invalid value
+                * if the corresponding swap type is swapoff. We double check
+                * the flags here. It's even possible the swap type is swapoff
+                * and swapon again and its priority is changed. In such rare
+                * case, low prority swap type might be used, but eventually
+                * high priority swap will be used after several rounds of
+                * swap.
+                */
+               if (hp_index != -1 && hp_index != type &&
+                   swap_info[type]->prio < swap_info[hp_index]->prio &&
+                   (swap_info[hp_index]->flags & SWP_WRITEOK)) {
+                       type = hp_index;
+                       swap_list.next = type;
+               }
+
                si = swap_info[type];
                next = si->next;
                if (next < 0 ||
@@ -432,22 +455,29 @@ swp_entry_t get_swap_page(void)
                        wrapped++;
                }
 
-               if (!si->highest_bit)
+               spin_lock(&si->lock);
+               if (!si->highest_bit) {
+                       spin_unlock(&si->lock);
                        continue;
-               if (!(si->flags & SWP_WRITEOK))
+               }
+               if (!(si->flags & SWP_WRITEOK)) {
+                       spin_unlock(&si->lock);
                        continue;
+               }
 
                swap_list.next = next;
+
+               spin_unlock(&swap_lock);
                /* This is called for allocating swap entry for cache */
                offset = scan_swap_map(si, SWAP_HAS_CACHE);
-               if (offset) {
-                       spin_unlock(&swap_lock);
+               spin_unlock(&si->lock);
+               if (offset)
                        return swp_entry(type, offset);
-               }
+               spin_lock(&swap_lock);
                next = swap_list.next;
        }
 
-       nr_swap_pages++;
+       atomic_long_inc(&nr_swap_pages);
 noswap:
        spin_unlock(&swap_lock);
        return (swp_entry_t) {0};
@@ -459,19 +489,19 @@ swp_entry_t get_swap_page_of_type(int type)
        struct swap_info_struct *si;
        pgoff_t offset;
 
-       spin_lock(&swap_lock);
        si = swap_info[type];
+       spin_lock(&si->lock);
        if (si && (si->flags & SWP_WRITEOK)) {
-               nr_swap_pages--;
+               atomic_long_dec(&nr_swap_pages);
                /* This is called for allocating swap entry, not cache */
                offset = scan_swap_map(si, 1);
                if (offset) {
-                       spin_unlock(&swap_lock);
+                       spin_unlock(&si->lock);
                        return swp_entry(type, offset);
                }
-               nr_swap_pages++;
+               atomic_long_inc(&nr_swap_pages);
        }
-       spin_unlock(&swap_lock);
+       spin_unlock(&si->lock);
        return (swp_entry_t) {0};
 }
 
@@ -493,7 +523,7 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
                goto bad_offset;
        if (!p->swap_map[offset])
                goto bad_free;
-       spin_lock(&swap_lock);
+       spin_lock(&p->lock);
        return p;
 
 bad_free:
@@ -511,6 +541,27 @@ out:
        return NULL;
 }
 
+/*
+ * This swap type frees swap entry, check if it is the highest priority swap
+ * type which just frees swap entry. get_swap_page() uses
+ * highest_priority_index to search highest priority swap type. The
+ * swap_info_struct.lock can't protect us if there are multiple swap types
+ * active, so we use atomic_cmpxchg.
+ */
+static void set_highest_priority_index(int type)
+{
+       int old_hp_index, new_hp_index;
+
+       do {
+               old_hp_index = atomic_read(&highest_priority_index);
+               if (old_hp_index != -1 &&
+                       swap_info[old_hp_index]->prio >= swap_info[type]->prio)
+                       break;
+               new_hp_index = type;
+       } while (atomic_cmpxchg(&highest_priority_index,
+               old_hp_index, new_hp_index) != old_hp_index);
+}
+
 static unsigned char swap_entry_free(struct swap_info_struct *p,
                                     swp_entry_t entry, unsigned char usage)
 {
@@ -553,10 +604,8 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
                        p->lowest_bit = offset;
                if (offset > p->highest_bit)
                        p->highest_bit = offset;
-               if (swap_list.next >= 0 &&
-                   p->prio > swap_info[swap_list.next]->prio)
-                       swap_list.next = p->type;
-               nr_swap_pages++;
+               set_highest_priority_index(p->type);
+               atomic_long_inc(&nr_swap_pages);
                p->inuse_pages--;
                frontswap_invalidate_page(p->type, offset);
                if (p->flags & SWP_BLKDEV) {
@@ -581,7 +630,7 @@ void swap_free(swp_entry_t entry)
        p = swap_info_get(entry);
        if (p) {
                swap_entry_free(p, entry, 1);
-               spin_unlock(&swap_lock);
+               spin_unlock(&p->lock);
        }
 }
 
@@ -598,7 +647,7 @@ void swapcache_free(swp_entry_t entry, struct page *page)
                count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
                if (page)
                        mem_cgroup_uncharge_swapcache(page, entry, count != 0);
-               spin_unlock(&swap_lock);
+               spin_unlock(&p->lock);
        }
 }
 
@@ -617,7 +666,7 @@ int page_swapcount(struct page *page)
        p = swap_info_get(entry);
        if (p) {
                count = swap_count(p->swap_map[swp_offset(entry)]);
-               spin_unlock(&swap_lock);
+               spin_unlock(&p->lock);
        }
        return count;
 }
@@ -706,7 +755,7 @@ int free_swap_and_cache(swp_entry_t entry)
                                page = NULL;
                        }
                }
-               spin_unlock(&swap_lock);
+               spin_unlock(&p->lock);
        }
        if (page) {
                /*
@@ -804,11 +853,13 @@ unsigned int count_swap_pages(int type, int free)
        if ((unsigned int)type < nr_swapfiles) {
                struct swap_info_struct *sis = swap_info[type];
 
+               spin_lock(&sis->lock);
                if (sis->flags & SWP_WRITEOK) {
                        n = sis->pages;
                        if (free)
                                n -= sis->inuse_pages;
                }
+               spin_unlock(&sis->lock);
        }
        spin_unlock(&swap_lock);
        return n;
@@ -1457,7 +1508,7 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio,
        p->swap_map = swap_map;
        frontswap_map_set(p, frontswap_map);
        p->flags |= SWP_WRITEOK;
-       nr_swap_pages += p->pages;
+       atomic_long_add(p->pages, &nr_swap_pages);
        total_swap_pages += p->pages;
 
        /* insert swap space into swap_list: */
@@ -1479,15 +1530,19 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
                                unsigned long *frontswap_map)
 {
        spin_lock(&swap_lock);
+       spin_lock(&p->lock);
        _enable_swap_info(p, prio, swap_map, frontswap_map);
        frontswap_init(p->type);
+       spin_unlock(&p->lock);
        spin_unlock(&swap_lock);
 }
 
 static void reinsert_swap_info(struct swap_info_struct *p)
 {
        spin_lock(&swap_lock);
+       spin_lock(&p->lock);
        _enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
+       spin_unlock(&p->lock);
        spin_unlock(&swap_lock);
 }
 
@@ -1547,14 +1602,16 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
                /* just pick something that's safe... */
                swap_list.next = swap_list.head;
        }
+       spin_lock(&p->lock);
        if (p->prio < 0) {
                for (i = p->next; i >= 0; i = swap_info[i]->next)
                        swap_info[i]->prio = p->prio--;
                least_priority++;
        }
-       nr_swap_pages -= p->pages;
+       atomic_long_sub(p->pages, &nr_swap_pages);
        total_swap_pages -= p->pages;
        p->flags &= ~SWP_WRITEOK;
+       spin_unlock(&p->lock);
        spin_unlock(&swap_lock);
 
        set_current_oom_origin();
@@ -1573,14 +1630,17 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
        mutex_lock(&swapon_mutex);
        spin_lock(&swap_lock);
+       spin_lock(&p->lock);
        drain_mmlist();
 
        /* wait for anyone still in scan_swap_map */
        p->highest_bit = 0;             /* cuts scans short */
        while (p->flags >= SWP_SCANNING) {
+               spin_unlock(&p->lock);
                spin_unlock(&swap_lock);
                schedule_timeout_uninterruptible(1);
                spin_lock(&swap_lock);
+               spin_lock(&p->lock);
        }
 
        swap_file = p->swap_file;
@@ -1590,6 +1650,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
        p->swap_map = NULL;
        p->flags = 0;
        frontswap_invalidate_area(type);
+       spin_unlock(&p->lock);
        spin_unlock(&swap_lock);
        mutex_unlock(&swapon_mutex);
        vfree(swap_map);
@@ -1795,6 +1856,7 @@ static struct swap_info_struct *alloc_swap_info(void)
        p->flags = SWP_USED;
        p->next = -1;
        spin_unlock(&swap_lock);
+       spin_lock_init(&p->lock);
 
        return p;
 }
@@ -2117,7 +2179,7 @@ void si_swapinfo(struct sysinfo *val)
                if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
                        nr_to_be_unused += si->inuse_pages;
        }
-       val->freeswap = nr_swap_pages + nr_to_be_unused;
+       val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
        val->totalswap = total_swap_pages + nr_to_be_unused;
        spin_unlock(&swap_lock);
 }
@@ -2150,7 +2212,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
        p = swap_info[type];
        offset = swp_offset(entry);
 
-       spin_lock(&swap_lock);
+       spin_lock(&p->lock);
        if (unlikely(offset >= p->max))
                goto unlock_out;
 
@@ -2185,7 +2247,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
        p->swap_map[offset] = count | has_cache;
 
 unlock_out:
-       spin_unlock(&swap_lock);
+       spin_unlock(&p->lock);
 out:
        return err;
 
@@ -2310,7 +2372,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
        }
 
        if (!page) {
-               spin_unlock(&swap_lock);
+               spin_unlock(&si->lock);
                return -ENOMEM;
        }
 
@@ -2358,7 +2420,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
        list_add_tail(&page->lru, &head->lru);
        page = NULL;                    /* now it's attached, don't free it */
 out:
-       spin_unlock(&swap_lock);
+       spin_unlock(&si->lock);
 outer:
        if (page)
                __free_page(page);
index a68fa20..b7d8015 100644 (file)
@@ -1684,7 +1684,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
                force_scan = true;
 
        /* If we have no swap space, do not bother scanning anon pages. */
-       if (!sc->may_swap || (nr_swap_pages <= 0)) {
+       if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
                scan_balance = SCAN_FILE;
                goto out;
        }
@@ -1933,7 +1933,7 @@ static inline bool should_continue_reclaim(struct zone *zone,
         */
        pages_for_compaction = (2UL << sc->order);
        inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
-       if (nr_swap_pages > 0)
+       if (get_nr_swap_pages() > 0)
                inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
        if (sc->nr_reclaimed < pages_for_compaction &&
                        inactive_lru_pages > pages_for_compaction)
@@ -3085,7 +3085,7 @@ unsigned long global_reclaimable_pages(void)
        nr = global_page_state(NR_ACTIVE_FILE) +
             global_page_state(NR_INACTIVE_FILE);
 
-       if (nr_swap_pages > 0)
+       if (get_nr_swap_pages() > 0)
                nr += global_page_state(NR_ACTIVE_ANON) +
                      global_page_state(NR_INACTIVE_ANON);
 
@@ -3099,7 +3099,7 @@ unsigned long zone_reclaimable_pages(struct zone *zone)
        nr = zone_page_state(zone, NR_ACTIVE_FILE) +
             zone_page_state(zone, NR_INACTIVE_FILE);
 
-       if (nr_swap_pages > 0)
+       if (get_nr_swap_pages() > 0)
                nr += zone_page_state(zone, NR_ACTIVE_ANON) +
                      zone_page_state(zone, NR_INACTIVE_ANON);