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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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