linux-kernel - [PATCH] cachefiles: allocate static minor for /dev/cachefiles

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Date:   Thu, 15 Jun 2023 18:08:06 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     linux-cachefs@...hat.com, linux-kernel@...r.kernel.org
Cc:     dhowells@...hat.com, arnd@...db.de, gregkh@...uxfoundation.org
Subject: [PATCH] cachefiles: allocate static minor for /dev/cachefiles

The cachefiles misc character device uses MISC_DYNAMIC_MINOR and thus
doesn't support module auto-loading. Assign a static minor number for it
and provide appropriate module aliases for it. This is enough for kmod to
create the /dev/cachefiles device node on startup and facility module
auto-loading.

Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
---
 Documentation/admin-guide/devices.txt | 3 ++-
 fs/cachefiles/main.c                  | 4 +++-
 include/linux/miscdevice.h            | 1 +
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index 06c525e01ea5..21b2dda10006 100644
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -376,8 +376,9 @@
 		240 = /dev/userio	Serio driver testing device
 		241 = /dev/vhost-vsock	Host kernel driver for virtio vsock
 		242 = /dev/rfkill	Turning off radio transmissions (rfkill)
+		243 = /dev/cachefiles	Filesystem caching on files
 
-		243-254			Reserved for local use
+		244-254			Reserved for local use
 		255			Reserved for MISC_DYNAMIC_MINOR
 
   11 char	Raw keyboard device	(Linux/SPARC only)
diff --git a/fs/cachefiles/main.c b/fs/cachefiles/main.c
index 3f369c6f816d..eead7b5016a7 100644
--- a/fs/cachefiles/main.c
+++ b/fs/cachefiles/main.c
@@ -30,11 +30,13 @@ MODULE_PARM_DESC(cachefiles_debug, "CacheFiles debugging mask");
 MODULE_DESCRIPTION("Mounted-filesystem based cache");
 MODULE_AUTHOR("Red Hat, Inc.");
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("devname:cachefiles");
+MODULE_ALIAS_MISCDEV(CACHEFILES_MINOR);
 
 struct kmem_cache *cachefiles_object_jar;
 
 static struct miscdevice cachefiles_dev = {
-	.minor	= MISC_DYNAMIC_MINOR,
+	.minor	= CACHEFILES_MINOR,
 	.name	= "cachefiles",
 	.fops	= &cachefiles_daemon_fops,
 };
diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index c0fea6ca5076..d7f989f593b0 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -71,6 +71,7 @@
 #define USERIO_MINOR		240
 #define VHOST_VSOCK_MINOR	241
 #define RFKILL_MINOR		242
+#define CACHEFILES_MINOR	243
 #define MISC_DYNAMIC_MINOR	255
 
 struct device;
-- 
2.40.1