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    Subject[PATCH 03/17] fs: icache lock inode hash
    Date
    From: Nick Piggin <npiggin@suse.de>

    Currently the inode hash lists are protected by the inode_lock. To
    allow removal of the inode_lock, we need to protect the inode hash
    table lists with a new lock. Nest the new inode_hash_lock inside the
    inode_lock to protect the hash lists.

    Signed-off-by: Nick Piggin <npiggin@suse.de>
    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    ---
    fs/inode.c | 33 ++++++++++++++++++++++++++++++++-
    include/linux/writeback.h | 1 +
    2 files changed, 33 insertions(+), 1 deletions(-)

    diff --git a/fs/inode.c b/fs/inode.c
    index ca98254..9d7ffb1 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -29,10 +29,14 @@
    * Usage:
    * sb_inode_list_lock protects:
    * s_inodes, i_sb_list
    + * inode_hash_lock protects:
    + * inode hash table, i_hash
    *
    * Ordering:
    * inode_lock
    * sb_inode_list_lock
    + * inode_lock
    + * inode_hash_lock
    */
    /*
    * This is needed for the following functions:
    @@ -93,6 +97,7 @@ static struct hlist_head *inode_hashtable __read_mostly;
    */
    DEFINE_SPINLOCK(inode_lock);
    DEFINE_SPINLOCK(sb_inode_list_lock);
    +DEFINE_SPINLOCK(inode_hash_lock);

    /*
    * iprune_sem provides exclusion between the kswapd or try_to_free_pages
    @@ -348,7 +353,9 @@ static void dispose_list(struct list_head *head)
    evict(inode);

    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_del_init(&inode->i_hash);
    + spin_unlock(&inode_hash_lock);
    spin_lock(&sb_inode_list_lock);
    list_del_init(&inode->i_sb_list);
    spin_unlock(&sb_inode_list_lock);
    @@ -557,17 +564,20 @@ static struct inode *find_inode(struct super_block *sb,
    struct inode *inode = NULL;

    repeat:
    + spin_lock(&inode_hash_lock);
    hlist_for_each_entry(inode, node, head, i_hash) {
    if (inode->i_sb != sb)
    continue;
    if (!test(inode, data))
    continue;
    if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
    + spin_unlock(&inode_hash_lock);
    __wait_on_freeing_inode(inode);
    goto repeat;
    }
    break;
    }
    + spin_unlock(&inode_hash_lock);
    return node ? inode : NULL;
    }

    @@ -582,17 +592,20 @@ static struct inode *find_inode_fast(struct super_block *sb,
    struct inode *inode = NULL;

    repeat:
    + spin_lock(&inode_hash_lock);
    hlist_for_each_entry(inode, node, head, i_hash) {
    if (inode->i_ino != ino)
    continue;
    if (inode->i_sb != sb)
    continue;
    if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
    + spin_unlock(&inode_hash_lock);
    __wait_on_freeing_inode(inode);
    goto repeat;
    }
    break;
    }
    + spin_unlock(&inode_hash_lock);
    return node ? inode : NULL;
    }

    @@ -615,8 +628,11 @@ __inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
    spin_lock(&sb_inode_list_lock);
    list_add(&inode->i_sb_list, &sb->s_inodes);
    spin_unlock(&sb_inode_list_lock);
    - if (head)
    + if (head) {
    + spin_lock(&inode_hash_lock);
    hlist_add_head(&inode->i_hash, head);
    + spin_unlock(&inode_hash_lock);
    + }
    }

    /**
    @@ -1094,7 +1110,9 @@ int insert_inode_locked(struct inode *inode)
    while (1) {
    struct hlist_node *node;
    struct inode *old = NULL;
    +
    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_for_each_entry(old, node, head, i_hash) {
    if (old->i_ino != ino)
    continue;
    @@ -1106,9 +1124,11 @@ int insert_inode_locked(struct inode *inode)
    }
    if (likely(!node)) {
    hlist_add_head(&inode->i_hash, head);
    + spin_unlock(&inode_hash_lock);
    spin_unlock(&inode_lock);
    return 0;
    }
    + spin_unlock(&inode_hash_lock);
    __iget(old);
    spin_unlock(&inode_lock);
    wait_on_inode(old);
    @@ -1134,6 +1154,7 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
    struct inode *old = NULL;

    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_for_each_entry(old, node, head, i_hash) {
    if (old->i_sb != sb)
    continue;
    @@ -1145,9 +1166,11 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
    }
    if (likely(!node)) {
    hlist_add_head(&inode->i_hash, head);
    + spin_unlock(&inode_hash_lock);
    spin_unlock(&inode_lock);
    return 0;
    }
    + spin_unlock(&inode_hash_lock);
    __iget(old);
    spin_unlock(&inode_lock);
    wait_on_inode(old);
    @@ -1172,7 +1195,9 @@ void __insert_inode_hash(struct inode *inode, unsigned long hashval)
    {
    struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_add_head(&inode->i_hash, head);
    + spin_unlock(&inode_hash_lock);
    spin_unlock(&inode_lock);
    }
    EXPORT_SYMBOL(__insert_inode_hash);
    @@ -1186,7 +1211,9 @@ EXPORT_SYMBOL(__insert_inode_hash);
    void remove_inode_hash(struct inode *inode)
    {
    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_del_init(&inode->i_hash);
    + spin_unlock(&inode_hash_lock);
    spin_unlock(&inode_lock);
    }
    EXPORT_SYMBOL(remove_inode_hash);
    @@ -1245,7 +1272,9 @@ static void iput_final(struct inode *inode)
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state &= ~I_WILL_FREE;
    inodes_stat.nr_unused--;
    + spin_lock(&inode_hash_lock);
    hlist_del_init(&inode->i_hash);
    + spin_unlock(&inode_hash_lock);
    }
    list_del_init(&inode->i_list);
    spin_lock(&sb_inode_list_lock);
    @@ -1257,7 +1286,9 @@ static void iput_final(struct inode *inode)
    spin_unlock(&inode_lock);
    evict(inode);
    spin_lock(&inode_lock);
    + spin_lock(&inode_hash_lock);
    hlist_del_init(&inode->i_hash);
    + spin_unlock(&inode_hash_lock);
    spin_unlock(&inode_lock);
    wake_up_inode(inode);
    BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
    diff --git a/include/linux/writeback.h b/include/linux/writeback.h
    index 9974edb..35d6e81 100644
    --- a/include/linux/writeback.h
    +++ b/include/linux/writeback.h
    @@ -11,6 +11,7 @@ struct backing_dev_info;

    extern spinlock_t inode_lock;
    extern spinlock_t sb_inode_list_lock;
    +extern spinlock_t inode_hash_lock;
    extern struct list_head inode_in_use;
    extern struct list_head inode_unused;

    --
    1.7.1


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