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    Subject[patch 43/52] fs: icache per-cpu nr_inodes counter
    From: Eric Dumazet <dada1@cosmosbay.com>

    Avoids cache line ping pongs between cpus and prepare next patch,
    because updates of nr_inodes dont need inode_lock anymore.

    Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
    Signed-off-by: Nick Piggin <npiggin@suse.de>
    ---
    fs/fs-writeback.c | 4 ++--
    fs/inode.c | 31 ++++++++++++++++++++++++++++---
    include/linux/fs.h | 5 ++++-
    kernel/sysctl.c | 4 ++--
    4 files changed, 36 insertions(+), 8 deletions(-)

    Index: linux-2.6/fs/fs-writeback.c
    ===================================================================
    --- linux-2.6.orig/fs/fs-writeback.c
    +++ linux-2.6/fs/fs-writeback.c
    @@ -904,7 +904,7 @@ static long wb_check_old_data_flush(stru
    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_inodes() - inodes_stat.nr_unused;

    if (nr_pages) {
    struct wb_writeback_args args = {
    @@ -1257,7 +1257,7 @@ void writeback_inodes_sb(struct super_bl
    long nr_to_write;

    nr_to_write = nr_dirty + nr_unstable +
    - inodes_stat.nr_inodes - inodes_stat.nr_unused;
    + get_nr_inodes() - inodes_stat.nr_unused;

    bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
    }
    Index: linux-2.6/fs/inode.c
    ===================================================================
    --- linux-2.6.orig/fs/inode.c
    +++ linux-2.6/fs/inode.c
    @@ -144,9 +144,33 @@ struct inodes_stat_t inodes_stat = {
    .nr_inodes = 0,
    .nr_unused = 0,
    };
    +struct percpu_counter nr_inodes;

    static struct kmem_cache *inode_cachep __read_mostly;

    +int get_nr_inodes(void)
    +{
    + return percpu_counter_sum_positive(&nr_inodes);
    +}
    +
    +/*
    + * Handle nr_dentry 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();
    + return proc_dointvec(table, write, buffer, lenp, ppos);
    +}
    +#else
    +int proc_nr_inodes(ctl_table *table, int write,
    + void __user *buffer, size_t *lenp, loff_t *ppos)
    +{
    + return -ENOSYS;
    +}
    +#endif
    +
    static void wake_up_inode(struct inode *inode)
    {
    /*
    @@ -657,8 +681,8 @@ __inode_add_to_lists(struct super_block
    {
    spin_lock(&sb_inode_list_lock);
    list_add_rcu(&inode->i_sb_list, &sb->s_inodes);
    - inodes_stat.nr_inodes++;
    spin_unlock(&sb_inode_list_lock);
    + percpu_counter_inc(&nr_inodes);
    if (b) {
    spin_lock_bucket(b);
    hlist_bl_add_head_rcu(&inode->i_hash, &b->head);
    @@ -1337,8 +1361,8 @@ void generic_delete_inode(struct inode *
    }
    spin_lock(&sb_inode_list_lock);
    list_del_rcu(&inode->i_sb_list);
    - inodes_stat.nr_inodes--;
    spin_unlock(&sb_inode_list_lock);
    + percpu_counter_dec(&nr_inodes);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_FREEING;
    spin_unlock(&inode->i_lock);
    @@ -1413,8 +1437,8 @@ int generic_detach_inode(struct inode *i
    }
    spin_lock(&sb_inode_list_lock);
    list_del_rcu(&inode->i_sb_list);
    - inodes_stat.nr_inodes--;
    spin_unlock(&sb_inode_list_lock);
    + percpu_counter_dec(&nr_inodes);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_FREEING;
    spin_unlock(&inode->i_lock);
    @@ -1723,6 +1747,7 @@ void __init inode_init(void)
    {
    int loop;

    + percpu_counter_init(&nr_inodes, 0);
    /* inode slab cache */
    inode_cachep = kmem_cache_create("inode_cache",
    sizeof(struct inode),
    Index: linux-2.6/include/linux/fs.h
    ===================================================================
    --- linux-2.6.orig/include/linux/fs.h
    +++ linux-2.6/include/linux/fs.h
    @@ -406,6 +406,8 @@ extern struct files_stat_struct files_st
    extern int get_max_files(void);
    extern int sysctl_nr_open;
    extern struct inodes_stat_t inodes_stat;
    +extern struct percpu_counter nr_inodes;
    +extern int get_nr_inodes(void);
    extern int leases_enable, lease_break_time;
    #ifdef CONFIG_DNOTIFY
    extern int dir_notify_enable;
    @@ -2514,7 +2516,8 @@ ssize_t simple_attr_write(struct file *f
    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])
    Index: linux-2.6/kernel/sysctl.c
    ===================================================================
    --- linux-2.6.orig/kernel/sysctl.c
    +++ linux-2.6/kernel/sysctl.c
    @@ -1338,14 +1338,14 @@ 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",



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