ALSA: core - Define llseek fops

Set no_llseek to llseek file ops of each sound component (but for hwdep).
This avoids the implicit BKL invocation via generic_file_llseek() used
as default when fops.llseek is NULL.

Also call nonseekable_open() at each open ops to ensure the file flags
have no seek bit.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/mixer_oss.c

@@ -43,6 +43,10 @@ static int snd_mixer_oss_open(struct inode *inode, struct file *file)
 	struct snd_mixer_oss_file *fmixer;
 	int err;
 
+	err = nonseekable_open(inode, file);
+	if (err < 0)
+		return err;
+
 	card = snd_lookup_oss_minor_data(iminor(inode),
 					 SNDRV_OSS_DEVICE_TYPE_MIXER);
 	if (card == NULL)
@@ -397,6 +401,7 @@ static const struct file_operations snd_mixer_oss_f_ops =
 	.owner =	THIS_MODULE,
 	.open =		snd_mixer_oss_open,
 	.release =	snd_mixer_oss_release,
+	.llseek =	no_llseek,
 	.unlocked_ioctl =	snd_mixer_oss_ioctl,
 	.compat_ioctl =	snd_mixer_oss_ioctl_compat,
 };