init: remove /proc/sys/kernel/real-root-dev

It is not used anymore.

Signed-off-by: Askar Safin <safinaskar@gmail.com>
Link: https://patch.msgid.link/20251119222407.3333257-4-safinaskar@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Askar Safin

Documentation/admin-guide/sysctl/kernel.rst

@@ -1235,12 +1235,6 @@ that support this feature.
 ==  ===========================================================================
 
 
-real-root-dev
-=============
-
-See Documentation/admin-guide/initrd.rst.
-
-
 reboot-cmd (SPARC only)
 =======================
 

include/uapi/linux/sysctl.h

@@ -92,7 +92,6 @@ enum
 	KERN_DOMAINNAME=8,	/* string: domainname */
 
 	KERN_PANIC=15,		/* int: panic timeout */
-	KERN_REALROOTDEV=16,	/* real root device to mount after initrd */
 
 	KERN_SPARC_REBOOT=21,	/* reboot command on Sparc */
 	KERN_CTLALTDEL=22,	/* int: allow ctl-alt-del to reboot */

init/do_mounts_initrd.c

@@ -8,31 +8,11 @@
 
 unsigned long initrd_start, initrd_end;
 int initrd_below_start_ok;
-static unsigned int real_root_dev;	/* do_proc_dointvec cannot handle kdev_t */
 static int __initdata mount_initrd = 1;
 
 phys_addr_t phys_initrd_start __initdata;
 unsigned long phys_initrd_size __initdata;
 
-#ifdef CONFIG_SYSCTL
-static const struct ctl_table kern_do_mounts_initrd_table[] = {
-	{
-		.procname       = "real-root-dev",
-		.data           = &real_root_dev,
-		.maxlen         = sizeof(int),
-		.mode           = 0644,
-		.proc_handler   = proc_dointvec,
-	},
-};
-
-static __init int kernel_do_mounts_initrd_sysctls_init(void)
-{
-	register_sysctl_init("kernel", kern_do_mounts_initrd_table);
-	return 0;
-}
-late_initcall(kernel_do_mounts_initrd_sysctls_init);
-#endif /* CONFIG_SYSCTL */
-
 static int __init no_initrd(char *str)
 {
 	pr_warn("noinitrd option is deprecated and will be removed soon\n");