Fix: metadata stream should not reference session

[lttng-modules.git] / lttng-abi.c

diff --git a/lttng-abi.c b/lttng-abi.c
index 26a456ece13f7ed0a62b5e3b3e92d2cff942c17c..1be6802a0f3c511677048e578476b71785e113d4 100644 (file)
--- a/lttng-abi.c
+++ b/lttng-abi.c
@@ -553,10 +553,9 @@ int lttng_metadata_ring_buffer_ioctl_get_next_subbuf(struct file *filp,
        struct lttng_metadata_stream *stream = filp->private_data;
        struct lib_ring_buffer *buf = stream->priv;
        struct channel *chan = buf->backend.chan;
-       struct lttng_channel *lttng_chan = channel_get_private(chan);
        int ret;
 
-       ret = lttng_metadata_output_channel(lttng_chan, stream);
+       ret = lttng_metadata_output_channel(stream, chan);
        if (ret > 0) {
                lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
                ret = 0;
@@ -671,6 +670,10 @@ err:
 }
 #endif
 
+/*
+ * This is not used by anonymous file descriptors. This code is left
+ * there if we ever want to implement an inode with open() operation.
+ */
 static
 int lttng_metadata_ring_buffer_open(struct inode *inode, struct file *file)
 {
@@ -678,6 +681,14 @@ int lttng_metadata_ring_buffer_open(struct inode *inode, struct file *file)
        struct lib_ring_buffer *buf = stream->priv;
 
        file->private_data = buf;
+       /*
+        * Since life-time of metadata cache differs from that of
+        * session, we need to keep our own reference on the transport.
+        */
+       if (!try_module_get(stream->transport->owner)) {
+               printk(KERN_WARNING "LTT : Can't lock transport module.\n");
+               return -EBUSY;
+       }
        return lib_ring_buffer_open(inode, file, buf);
 }
 
@@ -686,12 +697,9 @@ int lttng_metadata_ring_buffer_release(struct inode *inode, struct file *file)
 {
        struct lttng_metadata_stream *stream = file->private_data;
        struct lib_ring_buffer *buf = stream->priv;
-       struct channel *chan = buf->backend.chan;
-       struct lttng_channel *lttng_chan = channel_get_private(chan);
 
        kref_put(&stream->metadata_cache->refcount, metadata_cache_destroy);
-       fput(lttng_chan->file);
-
+       module_put(stream->transport->owner);
        return lib_ring_buffer_release(inode, file, buf);
 }
 
@@ -811,24 +819,41 @@ int lttng_abi_open_metadata_stream(struct file *channel_file)
 
        metadata_stream = kzalloc(sizeof(struct lttng_metadata_stream),
                        GFP_KERNEL);
-       if (!metadata_stream)
-               return -ENOMEM;
+       if (!metadata_stream) {
+               ret = -ENOMEM;
+               goto nomem;
+       }
        metadata_stream->metadata_cache = session->metadata_cache;
        init_waitqueue_head(&metadata_stream->read_wait);
        metadata_stream->priv = buf;
        stream_priv = metadata_stream;
+       metadata_stream->transport = channel->transport;
+
+       /*
+        * Since life-time of metadata cache differs from that of
+        * session, we need to keep our own reference on the transport.
+        */
+       if (!try_module_get(metadata_stream->transport->owner)) {
+               printk(KERN_WARNING "LTT : Can't lock transport module.\n");
+               ret = -EINVAL;
+               goto notransport;
+       }
+
        ret = lttng_abi_create_stream_fd(channel_file, stream_priv,
                        &lttng_metadata_ring_buffer_file_operations);
        if (ret < 0)
                goto fd_error;
 
-       atomic_long_inc(&channel_file->f_count);
        kref_get(&session->metadata_cache->refcount);
        list_add(&metadata_stream->list,
                &session->metadata_cache->metadata_stream);
        return ret;
 
 fd_error:
+       module_put(metadata_stream->transport->owner);
+notransport:
+       kfree(metadata_stream);
+nomem:
        channel->ops->buffer_read_close(buf);
        return ret;
 }