inode: convert inode_stat.nr_unused to per-cpu counters

Before we split up the inode_lru_lock, the unused inode counter
needs to be made independent of the global inode_lru_lock. Convert
it to per-cpu counters to do this.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 5 deletions

diff --git a/fs/inode.c b/fs/inode.c
index cbdcab88105f..9a0361121712 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -95,6 +95,7 @@ EXPORT_SYMBOL(empty_aops);
 struct inodes_stat_t inodes_stat;
 
 static DEFINE_PER_CPU(unsigned int, nr_inodes);
+static DEFINE_PER_CPU(unsigned int, nr_unused);
 
 static struct kmem_cache *inode_cachep __read_mostly;
 
@@ -109,7 +110,11 @@ static int get_nr_inodes(void)
 
 static inline int get_nr_inodes_unused(void)
 {
-        return inodes_stat.nr_unused;
+        int i;
+        int sum = 0;
+        for_each_possible_cpu(i)
+                sum += per_cpu(nr_unused, i);
+        return sum < 0 ? 0 : sum;
 }
 
 int get_nr_dirty_inodes(void)
@@ -127,6 +132,7 @@ int proc_nr_inodes(ctl_table *table, int write,
                    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
         inodes_stat.nr_inodes = get_nr_inodes();
+        inodes_stat.nr_unused = get_nr_inodes_unused();
         return proc_dointvec(table, write, buffer, lenp, ppos);
 }
 #endif
@@ -340,7 +346,7 @@ static void inode_lru_list_add(struct inode *inode)
         spin_lock(&inode_lru_lock);
         if (list_empty(&inode->i_lru)) {
                 list_add(&inode->i_lru, &inode_lru);
-                inodes_stat.nr_unused++;
+                this_cpu_inc(nr_unused);
         }
         spin_unlock(&inode_lru_lock);
 }
@@ -350,7 +356,7 @@ static void inode_lru_list_del(struct inode *inode)
         spin_lock(&inode_lru_lock);
         if (!list_empty(&inode->i_lru)) {
                 list_del_init(&inode->i_lru);
-                inodes_stat.nr_unused--;
+                this_cpu_dec(nr_unused);
         }
         spin_unlock(&inode_lru_lock);
 }
@@ -656,7 +662,7 @@ static void prune_icache(int nr_to_scan)
                     (inode->i_state & ~I_REFERENCED)) {
                         list_del_init(&inode->i_lru);
                         spin_unlock(&inode->i_lock);
-                        inodes_stat.nr_unused--;
+                        this_cpu_dec(nr_unused);
                         continue;
                 }
 
@@ -693,7 +699,7 @@ static void prune_icache(int nr_to_scan)
                 spin_unlock(&inode->i_lock);
 
                 list_move(&inode->i_lru, &freeable);
-                inodes_stat.nr_unused--;
+                this_cpu_dec(nr_unused);
         }
         if (current_is_kswapd())
                 __count_vm_events(KSWAPD_INODESTEAL, reap);