[PATCH] proper lseek locking in ALSA, take 3

The attached patch implements proper locking in ALSA lseek methods.
Note ALSA has 3 lseek implementations, but only:

	sound/core/info.c :: snd_info_entry_llseek()

requires locking.  I wrapped the function in the BKL.  According to
Jaroslav Kysela the gus_mem_proc method is only called from above.  The
third lseek, in hwdep.c, clearly doesn't need locking.  Without this
patch, the above lseek is not safe.

	Robert Love

sound/core/info.c

@@ -29,6 +29,7 @@
 #include <sound/info.h>
 #include <sound/version.h>
 #include <linux/proc_fs.h>
+#include <linux/smp_lock.h>
 #ifdef CONFIG_DEVFS_FS
 #include <linux/devfs_fs_kernel.h>
 #endif
@@ -162,31 +163,40 @@ static loff_t snd_info_entry_llseek(struct file *file, loff_t offset, int orig)
 {
 	snd_info_private_data_t *data;
 	struct snd_info_entry *entry;
+	int ret = -EINVAL;
 
 	data = snd_magic_cast(snd_info_private_data_t, file->private_data, return -ENXIO);
 	entry = data->entry;
+	lock_kernel();
 	switch (entry->content) {
 	case SNDRV_INFO_CONTENT_TEXT:
 		switch (orig) {
 		case 0:	/* SEEK_SET */
 			file->f_pos = offset;
-			return file->f_pos;
+			ret = file->f_pos;
+			goto out;
 		case 1:	/* SEEK_CUR */
 			file->f_pos += offset;
-			return file->f_pos;
+			ret = file->f_pos;
+			goto out;
 		case 2:	/* SEEK_END */
 		default:
-			return -EINVAL;
+			goto out;
 		}
 		break;
 	case SNDRV_INFO_CONTENT_DATA:
-		if (entry->c.ops->llseek)
-			return entry->c.ops->llseek(entry,
+		if (entry->c.ops->llseek) {
+			ret = entry->c.ops->llseek(entry,
 						    data->file_private_data,
 						    file, offset, orig);
+			goto out;
+		}
 		break;
 	}
-	return -ENXIO;
+	ret = -ENXIO;
+out:
+	unlock_kernel();
+	return ret;
 }
 
 static ssize_t snd_info_entry_read(struct file *file, char *buffer,