tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private
Change remove_event_file_dir() to clear ->i_private for every file we are going to remove. We need to check file->dir != NULL because event_create_dir() can fail. debugfs_remove_recursive(NULL) is fine but the patch moves it under the same check anyway for readability. spin_lock(d_lock) and "d_inode != NULL" check are not needed afaics, but I do not understand this code enough. tracing_open_generic_file() and tracing_release_generic_file() can go away, ftrace_enable_fops and ftrace_event_filter_fops() use tracing_open_generic() but only to check tracing_disabled. This fixes all races with event_remove() or instance_delete(). f_op->read/write/whatever can never use the freed file/call, all event/* files were changed to check and use ->i_private under event_mutex. Note: this doesn't not fix other problems, event_remove() can destroy the active ftrace_event_call, we need more changes but those changes are completely orthogonal. Link: http://lkml.kernel.org/r/20130728183527.GB16723@redhat.com Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -428,41 +428,25 @@ static void *event_file_data(struct file *filp)
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static void remove_event_file_dir(struct ftrace_event_file *file)
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{
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struct dentry *dir = file->dir;
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struct dentry *child;
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if (dir) {
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spin_lock(&dir->d_lock); /* probably unneeded */
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list_for_each_entry(child, &dir->d_subdirs, d_u.d_child) {
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if (child->d_inode) /* probably unneeded */
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child->d_inode->i_private = NULL;
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}
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spin_unlock(&dir->d_lock);
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debugfs_remove_recursive(dir);
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}
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list_del(&file->list);
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debugfs_remove_recursive(file->dir);
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remove_subsystem(file->system);
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kmem_cache_free(file_cachep, file);
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}
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/*
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* Open and update trace_array ref count.
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* Must have the current trace_array passed to it.
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*/
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static int tracing_open_generic_file(struct inode *inode, struct file *filp)
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{
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struct ftrace_event_file *file = inode->i_private;
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struct trace_array *tr = file->tr;
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int ret;
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if (trace_array_get(tr) < 0)
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return -ENODEV;
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ret = tracing_open_generic(inode, filp);
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if (ret < 0)
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trace_array_put(tr);
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return ret;
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}
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static int tracing_release_generic_file(struct inode *inode, struct file *filp)
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{
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struct ftrace_event_file *file = inode->i_private;
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struct trace_array *tr = file->tr;
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trace_array_put(tr);
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return 0;
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}
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/*
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* __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
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*/
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@ -1281,10 +1265,9 @@ static const struct file_operations ftrace_set_event_fops = {
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};
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static const struct file_operations ftrace_enable_fops = {
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.open = tracing_open_generic_file,
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.open = tracing_open_generic,
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.read = event_enable_read,
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.write = event_enable_write,
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.release = tracing_release_generic_file,
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.llseek = default_llseek,
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};
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