[ALSA] Handle file operations during snd_card disconnects using static file->f_op

Alsa used to kmalloc one file->f_op per file per disconnecting snd_card.
This led to oopses sometimes when file->f_op was freed before __fput()
finished.
Patch adds a virtual device for disconnect: VDD.
VDD consists of:
	LIST_HEAD(shutdown_files)
	    protected by DEFINE_SPINLOCK(shutdown_mutex)
	static struct file_operations snd_shutdown_f_ops
	    and functions assigned to it
	Additions to struct snd_monitor_file
	    to specify if instance is hidden by VDD or not.
A VDD's instance is
	created in snd_card_disconnect() under the card->files_lock.
	cleaned up in snd_card_file_remove() under the card->files_lock.

Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/sound/core.h b/include/sound/core.h
index b056ea925ecf..fa1ca0127bab 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -89,10 +89,10 @@ struct snd_device {
 struct snd_monitor_file {
         struct file *file;
         struct snd_monitor_file *next;
+        const struct file_operations *disconnected_f_op;
+        struct list_head shutdown_list;
 };
 
-struct snd_shutdown_f_ops;      /* define it later in init.c */
-
 /* main structure for soundcard */
 
 struct snd_card {