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    Subject[PATCH 14/21] fs: add a per-superblock lock for the inode list
    Date
    From: Dave Chinner <dchinner@redhat.com>

    To allow removal of the inode_lock, we first need to protect the
    superblock inode list with its own lock instead of using the
    inode_lock. Add a lock to the superblock to protect this list and
    nest the new lock inside the inode_lock around the list operations
    it needs to protect.

    Based on a patch originally from Nick Piggin.

    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    ---
    fs/drop_caches.c | 4 ++++
    fs/fs-writeback.c | 4 ++++
    fs/inode.c | 29 +++++++++++++++++++++++------
    fs/notify/inode_mark.c | 3 +++
    fs/quota/dquot.c | 6 ++++++
    fs/super.c | 1 +
    include/linux/fs.h | 1 +
    7 files changed, 42 insertions(+), 6 deletions(-)

    diff --git a/fs/drop_caches.c b/fs/drop_caches.c
    index 10c8c5a..dfe8cb1 100644
    --- a/fs/drop_caches.c
    +++ b/fs/drop_caches.c
    @@ -17,6 +17,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
    struct inode *inode, *toput_inode = NULL;

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
    continue;
    @@ -25,12 +26,15 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
    spin_lock(&inode->i_lock);
    inode->i_ref++;
    spin_unlock(&inode->i_lock);
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    invalidate_mapping_pages(inode->i_mapping, 0, -1);
    iput(toput_inode);
    toput_inode = inode;
    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    }
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    iput(toput_inode);
    }
    diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
    index 1fb5d95..676e048 100644
    --- a/fs/fs-writeback.c
    +++ b/fs/fs-writeback.c
    @@ -1031,6 +1031,7 @@ static void wait_sb_inodes(struct super_block *sb)
    WARN_ON(!rwsem_is_locked(&sb->s_umount));

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);

    /*
    * Data integrity sync. Must wait for all pages under writeback,
    @@ -1050,6 +1051,7 @@ static void wait_sb_inodes(struct super_block *sb)
    spin_lock(&inode->i_lock);
    inode->i_ref++;
    spin_unlock(&inode->i_lock);
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    /*
    * We hold a reference to 'inode' so it couldn't have
    @@ -1067,7 +1069,9 @@ static void wait_sb_inodes(struct super_block *sb)
    cond_resched();

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    }
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    iput(old_inode);
    }
    diff --git a/fs/inode.c b/fs/inode.c
    index da6b73b..734aadf 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -34,13 +34,18 @@
    * i_ref
    * inode hash lock protects:
    * inode hash table, i_hash
    + * sb inode lock protects:
    + * s_inodes, i_sb_list
    *
    * Lock orders
    * inode_lock
    * inode hash bucket lock
    * inode->i_lock
    + *
    + * inode_lock
    + * sb inode lock
    + * inode->i_lock
    */
    -
    /*
    * This is needed for the following functions:
    * - inode_has_buffers
    @@ -365,9 +370,13 @@ void inode_lru_list_del(struct inode *inode)
    }
    }

    -static inline void __inode_sb_list_add(struct inode *inode)
    +static void __inode_sb_list_add(struct inode *inode)
    {
    - list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
    + struct super_block *sb = inode->i_sb;
    +
    + spin_lock(&sb->s_inodes_lock);
    + list_add(&inode->i_sb_list, &sb->s_inodes);
    + spin_unlock(&sb->s_inodes_lock);
    }

    /**
    @@ -382,9 +391,13 @@ void inode_sb_list_add(struct inode *inode)
    }
    EXPORT_SYMBOL_GPL(inode_sb_list_add);

    -static inline void __inode_sb_list_del(struct inode *inode)
    +static void __inode_sb_list_del(struct inode *inode)
    {
    + struct super_block *sb = inode->i_sb;
    +
    + spin_lock(&sb->s_inodes_lock);
    list_del_init(&inode->i_sb_list);
    + spin_unlock(&sb->s_inodes_lock);
    }

    static unsigned long hash(struct super_block *sb, unsigned long hashval)
    @@ -507,7 +520,8 @@ static void dispose_list(struct list_head *head)
    /*
    * Invalidate all inodes for a device.
    */
    -static int invalidate_list(struct list_head *head, struct list_head *dispose)
    +static int invalidate_list(struct super_block *sb, struct list_head *head,
    + struct list_head *dispose)
    {
    struct list_head *next;
    int busy = 0;
    @@ -524,6 +538,7 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
    * shrink_icache_memory() away.
    */
    cond_resched_lock(&inode_lock);
    + cond_resched_lock(&sb->s_inodes_lock);

    next = next->next;
    if (tmp == head)
    @@ -562,8 +577,10 @@ int invalidate_inodes(struct super_block *sb)

    down_write(&iprune_sem);
    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    fsnotify_unmount_inodes(&sb->s_inodes);
    - busy = invalidate_list(&sb->s_inodes, &throw_away);
    + busy = invalidate_list(sb, &sb->s_inodes, &throw_away);
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);

    dispose_list(&throw_away);
    diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
    index 1a4c117..4ed0e43 100644
    --- a/fs/notify/inode_mark.c
    +++ b/fs/notify/inode_mark.c
    @@ -242,6 +242,7 @@ void fsnotify_unmount_inodes(struct list_head *list)

    list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
    struct inode *need_iput_tmp;
    + struct super_block *sb = inode->i_sb;

    /*
    * We cannot iref() an inode in state I_FREEING,
    @@ -290,6 +291,7 @@ void fsnotify_unmount_inodes(struct list_head *list)
    * will be added since the umount has begun. Finally,
    * iprune_mutex keeps shrink_icache_memory() away.
    */
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);

    if (need_iput_tmp)
    @@ -303,5 +305,6 @@ void fsnotify_unmount_inodes(struct list_head *list)
    iput(inode);

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    }
    }
    diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
    index 326df72..7ef5411 100644
    --- a/fs/quota/dquot.c
    +++ b/fs/quota/dquot.c
    @@ -897,6 +897,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
    #endif

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
    continue;
    @@ -912,6 +913,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
    spin_lock(&inode->i_lock);
    inode->i_ref++;
    spin_unlock(&inode->i_lock);
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);

    iput(old_inode);
    @@ -923,7 +925,9 @@ static void add_dquot_ref(struct super_block *sb, int type)
    * keep the reference and iput it later. */
    old_inode = inode;
    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    }
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    iput(old_inode);

    @@ -1006,6 +1010,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
    int reserved = 0;

    spin_lock(&inode_lock);
    + spin_lock(&sb->s_inodes_lock);
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    /*
    * We have to scan also I_NEW inodes because they can already
    @@ -1019,6 +1024,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
    remove_inode_dquot_ref(inode, type, tofree_head);
    }
    }
    + spin_unlock(&sb->s_inodes_lock);
    spin_unlock(&inode_lock);
    #ifdef CONFIG_QUOTA_DEBUG
    if (reserved) {
    diff --git a/fs/super.c b/fs/super.c
    index 8819e3a..c5332e5 100644
    --- a/fs/super.c
    +++ b/fs/super.c
    @@ -76,6 +76,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
    INIT_LIST_HEAD(&s->s_dentry_lru);
    init_rwsem(&s->s_umount);
    mutex_init(&s->s_lock);
    + spin_lock_init(&s->s_inodes_lock);
    lockdep_set_class(&s->s_umount, &type->s_umount_key);
    /*
    * The locking rules for s_lock are up to the
    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index adcbfb9..f222ce8 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -1347,6 +1347,7 @@ struct super_block {
    #endif
    const struct xattr_handler **s_xattr;

    + spinlock_t s_inodes_lock; /* lock for s_inodes */
    struct list_head s_inodes; /* all inodes */
    struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
    #ifdef CONFIG_SMP
    --
    1.7.1


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