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Subject[PATCH 03/20] fs: Convert nr_inodes and nr_unused to per-cpu counters
Date
From: Dave Chinner <dchinner@redhat.com>

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.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/fs-writeback.c | 5 +--
fs/inode.c | 64 ++++++++++++++++++++++++++++++++++++---------------
include/linux/fs.h | 4 ++-
kernel/sysctl.c | 4 +-
4 files changed, 52 insertions(+), 25 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index ab38fef..58a95b7 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -723,7 +723,7 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
wb->last_old_flush = jiffies;
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ get_nr_dirty_inodes();

if (nr_pages) {
struct wb_writeback_work work = {
@@ -1090,8 +1090,7 @@ void writeback_inodes_sb(struct super_block *sb)

WARN_ON(!rwsem_is_locked(&sb->s_umount));

- work.nr_pages = nr_dirty + nr_unstable +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ work.nr_pages = nr_dirty + nr_unstable + get_nr_dirty_inodes();

bdi_queue_work(sb->s_bdi, &work);
wait_for_completion(&done);
diff --git a/fs/inode.c b/fs/inode.c
index 8646433..b3b6a4b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -103,8 +103,41 @@ static DECLARE_RWSEM(iprune_sem);
*/
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
+ */
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+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 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
inode->i_fsnotify_mask = 0;
#endif

+ percpu_counter_inc(&nr_inodes);
+
return 0;
out:
return -ENOMEM;
@@ -232,6 +267,7 @@ void __destroy_inode(struct inode *inode)
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 @@ void __iget(struct inode *inode)

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 evict(struct inode *inode)
*/
static void dispose_list(struct list_head *head)
{
- int nr_disposed = 0;
-
while (!list_empty(head)) {
struct inode *inode;

@@ -344,11 +378,7 @@ static void dispose_list(struct list_head *head)

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 void dispose_list(struct list_head *head)
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 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
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;
}

@@ -448,7 +476,6 @@ static int can_unuse(struct inode *inode)
static void prune_icache(int nr_to_scan)
{
LIST_HEAD(freeable);
- int nr_pruned = 0;
int nr_scanned;
unsigned long reap = 0;

@@ -484,9 +511,8 @@ static void prune_icache(int nr_to_scan)
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
@@ -518,7 +544,7 @@ static int shrink_icache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
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 = {
@@ -595,7 +621,6 @@ static inline void
__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)
@@ -1215,7 +1240,7 @@ static void iput_final(struct inode *inode)
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;
@@ -1227,14 +1252,13 @@ static void iput_final(struct inode *inode)
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);
@@ -1503,6 +1527,8 @@ void __init inode_init(void)
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)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 63d069b..1fb92f9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -407,6 +407,7 @@ extern struct files_stat_struct files_stat;
extern int get_max_files(void);
extern int sysctl_nr_open;
extern struct inodes_stat_t inodes_stat;
+extern int get_nr_dirty_inodes(void);
extern int leases_enable, lease_break_time;

struct buffer_head;
@@ -2474,7 +2475,8 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
struct ctl_table;
int proc_nr_files(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
-
+int proc_nr_inodes(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
int __init get_filesystem_list(char *buf);

#define ACC_MODE(x) ("\004\002\006\006"[(x)&O_ACCMODE])
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f88552c..33d1733 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1340,14 +1340,14 @@ static struct ctl_table fs_table[] = {
.data = &inodes_stat,
.maxlen = 2*sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_nr_inodes,
},
{
.procname = "inode-state",
.data = &inodes_stat,
.maxlen = 7*sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_nr_inodes,
},
{
.procname = "file-nr",
--
1.7.1


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