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    Subject[PATCH 31/46] 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(-)

    diff --git a/fs/inode.c b/fs/inode.c
    index 26a8ac1..853e0c6 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -255,6 +255,12 @@ static struct inode *alloc_inode(struct super_block *sb)
    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));
    diff --git a/fs/pipe.c b/fs/pipe.c
    index a8012a9..4ae1d76 100644
    --- a/fs/pipe.c
    +++ b/fs/pipe.c
    @@ -1241,6 +1241,10 @@ out:
    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
    @@ -1250,7 +1254,7 @@ out:
    static struct dentry *pipefs_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
    {
    - return mount_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
    + return mount_pseudo(fs_type, "pipe:", &pipefs_ops, PIPEFS_MAGIC);
    }

    static struct file_system_type pipe_fs_type = {
    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index 280d11c..03937b7 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -2232,6 +2232,7 @@ extern void iget_failed(struct inode *);
    extern void end_writeback(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 *);

    diff --git a/include/linux/net.h b/include/linux/net.h
    index 06bde49..16faa13 100644
    --- a/include/linux/net.h
    +++ b/include/linux/net.h
    @@ -120,6 +120,7 @@ enum sock_shutdown_cmd {
    struct socket_wq {
    wait_queue_head_t wait;
    struct fasync_struct *fasync_list;
    + struct rcu_head rcu;
    } ____cacheline_aligned_in_smp;

    /**
    diff --git a/net/socket.c b/net/socket.c
    index d2504c6..425da53 100644
    --- a/net/socket.c
    +++ b/net/socket.c
    @@ -262,20 +262,21 @@ static struct inode *sock_alloc_inode(struct super_block *sb)
    }


    -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)
    --
    1.7.1


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