Hi all,
I have some questions concerning to the file storage gadget (g_file_storage) and its
compilation as built-in driver: AFAIK, the driver initialization fails cause the file
system is not available when the driver tries to init the backing file (please correct me
if I'm wrong). Now, for solving this issue I have used a notifier-chain that informs about
the availability of the root file system (see below patch). This implementation works when
the driver is compiled as loadable module too.
Now to my questions: Do you see any disavantages in my proposed solution? Do you expect
any problems when using a notifier in that way? Or do you have a better idea for solving
the mentioned issue?
Thanks in advance, and sorry for the possible silly questions,
Luis
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index c4e62a6..63daf2f 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -4132,7 +4132,7 @@ static int __init fsg_alloc(void)
}
-static int __init fsg_init(void)
+static int __init fsg_init_rootfs(void)
{
int rc;
struct fsg_dev *fsg;
@@ -4144,6 +4144,24 @@ static int __init fsg_init(void)
kref_put(&fsg->ref, fsg_release);
return rc;
}
+
+static int mount_rootfs_notifier_event(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ int ret;
+ ret = fsg_init_rootfs();
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block mount_rootfs_fsg_notifier = {
+ .notifier_call = mount_rootfs_notifier_event,
+};
+
+static int __init fsg_init(void)
+{
+ return mount_rootfs_register_notifier(&mount_rootfs_fsg_notifier);
+}
+
module_init(fsg_init);
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index b86fa2f..9443a8b 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -151,6 +151,21 @@ extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
unsigned long val, void *v, int nr_to_call, int *nr_calls);
+extern int __mount_rootfs_register_notifier(struct notifier_block *nb);
+extern int __mount_rootfs_unregister_notifier(struct notifier_block *nb);
+
+#if defined(MODULE)
+static inline int mount_rootfs_register_notifier(struct notifier_block *nb)
+{
+ int ret = -EINVAL;
+ if (nb->notifier_call)
+ ret = nb->notifier_call(nb, 0, NULL);
+ return ret;
+}
+#else
+# define mount_rootfs_register_notifier(nb) __mount_rootfs_register_notifier(nb)
+#endif
+
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
diff --git a/init/do_mounts.c b/init/do_mounts.c
index d055b19..33a16e2 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -29,6 +29,10 @@ static int __initdata root_wait;
dev_t ROOT_DEV;
+/* Internal variables for the mounted rootfs notification */
+static struct work_struct mount_rootfs_worker;
+static RAW_NOTIFIER_HEAD(mount_rootfs_chain);
+
static int __init load_ramdisk(char *str)
{
rd_doload = simple_strtol(str,NULL,0) & 3;
@@ -212,6 +216,24 @@ static void __init get_fs_names(char *page)
*s = '\0';
}
+static void mount_rootfs_notifier_work_func(struct work_struct *work)
+{
+ raw_notifier_call_chain(&mount_rootfs_chain, 0, NULL);
+}
+
+int __mount_rootfs_register_notifier(struct notifier_block *nb)
+{
+ return raw_notifier_chain_register(&mount_rootfs_chain, nb);
+}
+
+int __mount_rootfs_unregister_notifier(struct notifier_block *nb)
+{
+ return raw_notifier_chain_unregister(&mount_rootfs_chain, nb);
+}
+
+EXPORT_SYMBOL(__mount_rootfs_register_notifier);
+EXPORT_SYMBOL(__mount_rootfs_unregister_notifier);
+
static int __init do_mount_root(char *name, char *fs, int flags, void *data)
{
int err = sys_mount(name, "/root", fs, flags, data);
@@ -224,6 +246,11 @@ static int __init do_mount_root(char *name, char *fs, int flags, void
*data)
current->fs->pwd.mnt->mnt_sb->s_type->name,
current->fs->pwd.mnt->mnt_sb->s_flags & MS_RDONLY ?
" readonly" : "");
+
+ /* Init the data for the rootfs notifier */
+ INIT_WORK(&mount_rootfs_worker, mount_rootfs_notifier_work_func);
+ schedule_work(&mount_rootfs_worker);
+
return 0;
}
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