fs: Convert nr_inodes and nr_unused to per-cpu counters
The number of inodes allocated does not need to be tied to the
addition or removal of an inode to/from a list. If we are not tied
to a list lock, we could update the counters when inodes are
initialised or destroyed, but to do that we need to convert the
counters to be per-cpu (i.e. independent of a lock). This means that
we have the freedom to change the list/locking implementation
without needing to care about the counters.
Based on a patch originally from Eric Dumazet.
[AV: cleaned up a bit, fixed build breakage on weird configs
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/inode.c b/fs/inode.c
index 4440cf1..0d5aecc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -103,8 +103,41 @@
*/
struct inodes_stat_t inodes_stat;
+static struct percpu_counter nr_inodes __cacheline_aligned_in_smp;
+static struct percpu_counter nr_inodes_unused __cacheline_aligned_in_smp;
+
static struct kmem_cache *inode_cachep __read_mostly;
+static inline int get_nr_inodes(void)
+{
+ return percpu_counter_sum_positive(&nr_inodes);
+}
+
+static inline int get_nr_inodes_unused(void)
+{
+ return percpu_counter_sum_positive(&nr_inodes_unused);
+}
+
+int get_nr_dirty_inodes(void)
+{
+ int nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
+ return nr_dirty > 0 ? nr_dirty : 0;
+
+}
+
+/*
+ * Handle nr_inode sysctl
+ */
+#ifdef CONFIG_SYSCTL
+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
+
static void wake_up_inode(struct inode *inode)
{
/*
@@ -192,6 +225,8 @@
inode->i_fsnotify_mask = 0;
#endif
+ percpu_counter_inc(&nr_inodes);
+
return 0;
out:
return -ENOMEM;
@@ -232,6 +267,7 @@
if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
posix_acl_release(inode->i_default_acl);
#endif
+ percpu_counter_dec(&nr_inodes);
}
EXPORT_SYMBOL(__destroy_inode);
@@ -286,7 +322,7 @@
if (!(inode->i_state & (I_DIRTY|I_SYNC)))
list_move(&inode->i_list, &inode_in_use);
- inodes_stat.nr_unused--;
+ percpu_counter_dec(&nr_inodes_unused);
}
void end_writeback(struct inode *inode)
@@ -327,8 +363,6 @@
*/
static void dispose_list(struct list_head *head)
{
- int nr_disposed = 0;
-
while (!list_empty(head)) {
struct inode *inode;
@@ -344,11 +378,7 @@
wake_up_inode(inode);
destroy_inode(inode);
- nr_disposed++;
}
- spin_lock(&inode_lock);
- inodes_stat.nr_inodes -= nr_disposed;
- spin_unlock(&inode_lock);
}
/*
@@ -357,7 +387,7 @@
static int invalidate_list(struct list_head *head, struct list_head *dispose)
{
struct list_head *next;
- int busy = 0, count = 0;
+ int busy = 0;
next = head->next;
for (;;) {
@@ -383,13 +413,11 @@
list_move(&inode->i_list, dispose);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
- count++;
+ percpu_counter_dec(&nr_inodes_unused);
continue;
}
busy = 1;
}
- /* only unused inodes may be cached with i_count zero */
- inodes_stat.nr_unused -= count;
return busy;
}
@@ -447,7 +475,6 @@
static void prune_icache(int nr_to_scan)
{
LIST_HEAD(freeable);
- int nr_pruned = 0;
int nr_scanned;
unsigned long reap = 0;
@@ -483,9 +510,8 @@
list_move(&inode->i_list, &freeable);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
- nr_pruned++;
+ percpu_counter_dec(&nr_inodes_unused);
}
- inodes_stat.nr_unused -= nr_pruned;
if (current_is_kswapd())
__count_vm_events(KSWAPD_INODESTEAL, reap);
else
@@ -517,7 +543,7 @@
return -1;
prune_icache(nr);
}
- return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
+ return (get_nr_inodes_unused() / 100) * sysctl_vfs_cache_pressure;
}
static struct shrinker icache_shrinker = {
@@ -594,7 +620,6 @@
__inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
struct inode *inode)
{
- inodes_stat.nr_inodes++;
list_add(&inode->i_list, &inode_in_use);
list_add(&inode->i_sb_list, &sb->s_inodes);
if (head)
@@ -1214,7 +1239,7 @@
if (!drop) {
if (!(inode->i_state & (I_DIRTY|I_SYNC)))
list_move(&inode->i_list, &inode_unused);
- inodes_stat.nr_unused++;
+ percpu_counter_inc(&nr_inodes_unused);
if (sb->s_flags & MS_ACTIVE) {
spin_unlock(&inode_lock);
return;
@@ -1226,14 +1251,13 @@
spin_lock(&inode_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state &= ~I_WILL_FREE;
- inodes_stat.nr_unused--;
+ percpu_counter_dec(&nr_inodes_unused);
hlist_del_init(&inode->i_hash);
}
list_del_init(&inode->i_list);
list_del_init(&inode->i_sb_list);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
- inodes_stat.nr_inodes--;
spin_unlock(&inode_lock);
evict(inode);
spin_lock(&inode_lock);
@@ -1502,6 +1526,8 @@
SLAB_MEM_SPREAD),
init_once);
register_shrinker(&icache_shrinker);
+ percpu_counter_init(&nr_inodes, 0);
+ percpu_counter_init(&nr_inodes_unused, 0);
/* Hash may have been set up in inode_init_early */
if (!hashdist)