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    Subject[patch 18/35] fs: avoid inode RCU freeing for pseudo fs
    Pseudo filesystems that don't put inode on RCU list or reachable by
    rcu-walk dentries do not need to RCU free their inodes.

    Signed-off-by: Nick Piggin <npiggin@kernel.dk>

    ---
    fs/inode.c | 6 ++++++
    fs/pipe.c | 6 +++++-
    include/linux/fs.h | 1 +
    include/linux/net.h | 1 +
    net/socket.c | 17 +++++++++--------
    5 files changed, 22 insertions(+), 9 deletions(-)

    Index: linux-2.6/net/socket.c
    ===================================================================
    --- linux-2.6.orig/net/socket.c 2010-10-19 14:18:59.000000000 +1100
    +++ linux-2.6/net/socket.c 2010-10-19 14:19:22.000000000 +1100
    @@ -262,20 +262,21 @@
    }


    -static void sock_free_rcu(struct rcu_head *head)
    +
    +static void wq_free_rcu(struct rcu_head *head)
    {
    - struct inode *inode = container_of(head, struct inode, i_rcu);
    - struct socket_alloc *ei = container_of(inode, struct socket_alloc,
    - vfs_inode);
    + struct socket_wq *wq = container_of(head, struct socket_wq, rcu);

    - kfree(ei->socket.wq);
    - INIT_LIST_HEAD(&inode->i_dentry);
    - kmem_cache_free(sock_inode_cachep, ei);
    + kfree(wq);
    }

    static void sock_destroy_inode(struct inode *inode)
    {
    - call_rcu(&inode->i_rcu, sock_free_rcu);
    + struct socket_alloc *ei;
    +
    + ei = container_of(inode, struct socket_alloc, vfs_inode);
    + call_rcu(&ei->socket.wq->rcu, wq_free_rcu);
    + kmem_cache_free(sock_inode_cachep, ei);
    }

    static void init_once(void *foo)
    Index: linux-2.6/fs/inode.c
    ===================================================================
    --- linux-2.6.orig/fs/inode.c 2010-10-19 14:18:59.000000000 +1100
    +++ linux-2.6/fs/inode.c 2010-10-19 14:19:25.000000000 +1100
    @@ -263,6 +263,12 @@
    return inode;
    }

    +void free_inode_nonrcu(struct inode *inode)
    +{
    + kmem_cache_free(inode_cachep, inode);
    +}
    +EXPORT_SYMBOL(free_inode_nonrcu);
    +
    void __destroy_inode(struct inode *inode)
    {
    BUG_ON(inode_has_buffers(inode));
    Index: linux-2.6/fs/pipe.c
    ===================================================================
    --- linux-2.6.orig/fs/pipe.c 2010-10-19 14:17:18.000000000 +1100
    +++ linux-2.6/fs/pipe.c 2010-10-19 14:19:22.000000000 +1100
    @@ -1239,6 +1239,10 @@
    return ret;
    }

    +static const struct super_operations pipefs_ops = {
    + .destroy_inode = free_inode_nonrcu,
    +};
    +
    /*
    * pipefs should _never_ be mounted by userland - too much of security hassle,
    * no real gain from having the whole whorehouse mounted. So we don't need
    @@ -1249,7 +1253,7 @@
    int flags, const char *dev_name, void *data,
    struct vfsmount *mnt)
    {
    - return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
    + return get_sb_pseudo(fs_type, "pipe:", &pipefs_ops, PIPEFS_MAGIC, mnt);
    }

    static struct file_system_type pipe_fs_type = {
    Index: linux-2.6/include/linux/fs.h
    ===================================================================
    --- linux-2.6.orig/include/linux/fs.h 2010-10-19 14:18:59.000000000 +1100
    +++ linux-2.6/include/linux/fs.h 2010-10-19 14:19:24.000000000 +1100
    @@ -2196,6 +2196,7 @@
    extern void destroy_inode(struct inode *);
    extern void __destroy_inode(struct inode *);
    extern struct inode *new_inode(struct super_block *);
    +extern void free_inode_nonrcu(struct inode *inode);
    extern int should_remove_suid(struct dentry *);
    extern int file_remove_suid(struct file *);

    Index: linux-2.6/include/linux/net.h
    ===================================================================
    --- linux-2.6.orig/include/linux/net.h 2010-10-19 14:18:59.000000000 +1100
    +++ linux-2.6/include/linux/net.h 2010-10-19 14:18:59.000000000 +1100
    @@ -120,6 +120,7 @@
    struct socket_wq {
    wait_queue_head_t wait;
    struct fasync_struct *fasync_list;
    + struct rcu_head rcu;
    } ____cacheline_aligned_in_smp;

    /**



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