Merge tag 'vfs-7.0-rc1.initrd' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs initrd removal from Christian Brauner:
 "Remove the deprecated linuxrc-based initrd code path and related dead
  code. The linuxrc initrd path was deprecated in 2020 and this series
  completes its removal. If we see real-life regressions we'll revert.

  The core change removes handle_initrd() and init_linuxrc() — the
  entire flow that ran /linuxrc from an initrd, pivoted roots, and
  handed off to the real root filesystem. With that gone, initrd_load()
  becomes void (no longer short-circuits prepare_namespace()),
  rd_load_image() is simplified to always load /initrd.image instead of
  taking a path, and rd_load_disk() is deleted.

  The /proc/sys/kernel/real-root-dev sysctl and its backing variable are
  removed since they only existed for linuxrc to communicate the real
  root device back to the kernel.

  The no-op load_ramdisk= and prompt_ramdisk= parameters are dropped,
  and noinitrd and ramdisk_start= gain deprecation warnings.

  Initramfs is entirely unaffected. The non-linuxrc initrd path
  (root=/dev/ram0) is preserved but now carries a deprecation warning
  targeting January 2027 removal"

* tag 'vfs-7.0-rc1.initrd' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  init: remove /proc/sys/kernel/real-root-dev
  initrd: remove deprecated code path (linuxrc)
  init: remove deprecated "load_ramdisk" and "prompt_ramdisk" command line parameters

Author: torvalds

Documentation/admin-guide/kernel-parameters.txt

@@ -3477,8 +3477,6 @@ Kernel parameters
 			Enable Live Update Orchestrator (LUO).
 			Default: off.
 
-	load_ramdisk=	[RAM] [Deprecated]
-
 	lockd.nlm_grace_period=P  [NFS] Assign grace period.
 			Format: <integer>
 
@@ -4484,8 +4482,10 @@ Kernel parameters
 			Note that this argument takes precedence over
 			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
 
-	noinitrd	[RAM] Tells the kernel not to load any configured
-			initial RAM disk.
+	noinitrd	[Deprecated,RAM] Tells the kernel not to load any configured
+			initial RAM disk. Currently this parameter applies to
+			initrd only, not to initramfs. But it applies to both
+			in EFI mode.
 
 	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
 			remapping.
@@ -5442,8 +5442,6 @@ Kernel parameters
 			Param: <number> - step/bucket size as a power of 2 for
 				statistical time based profiling.
 
-	prompt_ramdisk=	[RAM] [Deprecated]
-
 	prot_virt=	[S390] enable hosting protected virtual machines
 			isolated from the hypervisor (if hardware supports
 			that). If enabled, the default kernel base address
@@ -5500,7 +5498,7 @@ Kernel parameters
 	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
 			See Documentation/admin-guide/blockdev/ramdisk.rst.
 
-	ramdisk_start=	[RAM] RAM disk image start address
+	ramdisk_start=	[Deprecated,RAM] RAM disk image start address
 
 	random.trust_cpu=off
 			[KNL,EARLY] Disable trusting the use of the CPU's

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)
 =======================
 

arch/arm/configs/neponset_defconfig

@@ -9,7 +9,7 @@ CONFIG_ASSABET_NEPONSET=y
 CONFIG_ZBOOT_ROM_TEXT=0x80000
 CONFIG_ZBOOT_ROM_BSS=0xc1000000
 CONFIG_ZBOOT_ROM=y
-CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) load_ramdisk=1 prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
+CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) mem=32M noinitrd initrd=0xc0800000,3M"
 CONFIG_FPE_NWFPE=y
 CONFIG_PM=y
 CONFIG_MODULES=y

include/linux/initrd.h

@@ -3,8 +3,6 @@
 #ifndef __LINUX_INITRD_H
 #define __LINUX_INITRD_H
 
-#define INITRD_MINOR 250 /* shouldn't collide with /dev/ram* too soon ... */
-
 /* starting block # of image */
 extern int rd_image_start;
 

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.c

@@ -34,13 +34,6 @@ static int root_wait;
 
 dev_t ROOT_DEV;
 
-static int __init load_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated load_ramdisk= option\n");
-	return 1;
-}
-__setup("load_ramdisk=", load_ramdisk);
-
 static int __init readonly(char *str)
 {
 	if (*str)
@@ -484,13 +477,11 @@ void __init prepare_namespace(void)
 	if (saved_root_name[0])
 		ROOT_DEV = parse_root_device(saved_root_name);
 
-	if (initrd_load(saved_root_name))
-		goto out;
+	initrd_load();
 
 	if (root_wait)
 		wait_for_root(saved_root_name);
 	mount_root(saved_root_name);
-out:
 	devtmpfs_mount();
 	init_mount(".", "/", NULL, MS_MOVE, NULL);
 	init_chroot(".");

init/do_mounts.h

@@ -23,25 +23,15 @@ static inline __init int create_dev(char *name, dev_t dev)
 }
 
 #ifdef CONFIG_BLK_DEV_RAM
-
-int __init rd_load_disk(int n);
-int __init rd_load_image(char *from);
-
+int __init rd_load_image(void);
 #else
-
-static inline int rd_load_disk(int n) { return 0; }
-static inline int rd_load_image(char *from) { return 0; }
-
+static inline int rd_load_image(void) { return 0; }
 #endif
 
 #ifdef CONFIG_BLK_DEV_INITRD
-bool __init initrd_load(char *root_device_name);
+void __init initrd_load(void);
 #else
-static inline bool initrd_load(char *root_device_name)
-{
-	return false;
-	}
-
+static inline void initrd_load(void) { }
 #endif
 
 /* Ensure that async file closing finished to prevent spurious errors. */

init/do_mounts_initrd.c

@@ -2,45 +2,20 @@
 #include <linux/unistd.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>
-#include <linux/minix_fs.h>
-#include <linux/romfs_fs.h>
 #include <linux/initrd.h>
-#include <linux/sched.h>
-#include <linux/freezer.h>
-#include <linux/kmod.h>
-#include <uapi/linux/mount.h>
 
 #include "do_mounts.h"
 
 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");
 	mount_initrd = 0;
 	return 1;
 }
@@ -70,85 +45,19 @@ static int __init early_initrd(char *p)
 }
 early_param("initrd", early_initrd);
 
-static int __init init_linuxrc(struct subprocess_info *info, struct cred *new)
-{
-	ksys_unshare(CLONE_FS | CLONE_FILES);
-	console_on_rootfs();
-	/* move initrd over / and chdir/chroot in initrd root */
-	init_chdir("/root");
-	init_mount(".", "/", NULL, MS_MOVE, NULL);
-	init_chroot(".");
-	ksys_setsid();
-	return 0;
-}
-
-static void __init handle_initrd(char *root_device_name)
-{
-	struct subprocess_info *info;
-	static char *argv[] = { "linuxrc", NULL, };
-	extern char *envp_init[];
-	int error;
-
-	pr_warn("using deprecated initrd support, will be removed soon.\n");
-
-	real_root_dev = new_encode_dev(ROOT_DEV);
-	create_dev("/dev/root.old", Root_RAM0);
-	/* mount initrd on rootfs' /root */
-	mount_root_generic("/dev/root.old", root_device_name,
-			   root_mountflags & ~MS_RDONLY);
-	init_mkdir("/old", 0700);
-	init_chdir("/old");
-
-	info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
-					 GFP_KERNEL, init_linuxrc, NULL, NULL);
-	if (!info)
-		return;
-	call_usermodehelper_exec(info, UMH_WAIT_PROC|UMH_FREEZABLE);
-
-	/* move initrd to rootfs' /old */
-	init_mount("..", ".", NULL, MS_MOVE, NULL);
-	/* switch root and cwd back to / of rootfs */
-	init_chroot("..");
-
-	if (new_decode_dev(real_root_dev) == Root_RAM0) {
-		init_chdir("/old");
-		return;
-	}
-
-	init_chdir("/");
-	ROOT_DEV = new_decode_dev(real_root_dev);
-	mount_root(root_device_name);
-
-	printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
-	error = init_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
-	if (!error)
-		printk("okay\n");
-	else {
-		if (error == -ENOENT)
-			printk("/initrd does not exist. Ignored.\n");
-		else
-			printk("failed\n");
-		printk(KERN_NOTICE "Unmounting old root\n");
-		init_umount("/old", MNT_DETACH);
-	}
-}
-
-bool __init initrd_load(char *root_device_name)
+void __init initrd_load(void)
 {
 	if (mount_initrd) {
 		create_dev("/dev/ram", Root_RAM0);
 		/*
-		 * Load the initrd data into /dev/ram0. Execute it as initrd
-		 * unless /dev/ram0 is supposed to be our actual root device,
-		 * in that case the ram disk is just set up here, and gets
-		 * mounted in the normal path.
+		 * Load the initrd data into /dev/ram0.
 		 */
-		if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
-			init_unlink("/initrd.image");
-			handle_initrd(root_device_name);
-			return true;
+		if (rd_load_image()) {
+			pr_warn("using deprecated initrd support, will be removed in January 2027; "
+				"use initramfs instead or (as a last resort) /sys/firmware/initrd; "
+				"see section \"Workaround\" in "
+				"https://lore.kernel.org/lkml/20251010094047.3111495-1-safinaskar@gmail.com\n");
 		}
 	}
 	init_unlink("/initrd.image");
-	return false;
 }

init/do_mounts_rd.c

@@ -18,17 +18,11 @@
 static struct file *in_file, *out_file;
 static loff_t in_pos, out_pos;
 
-static int __init prompt_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated prompt_ramdisk= option\n");
-	return 1;
-}
-__setup("prompt_ramdisk=", prompt_ramdisk);
-
 int __initdata rd_image_start;		/* starting block # of image */
 
 static int __init ramdisk_start_setup(char *str)
 {
+	pr_warn("ramdisk_start= option is deprecated and will be removed soon\n");
 	return kstrtoint(str, 0, &rd_image_start) == 0;
 }
 __setup("ramdisk_start=", ramdisk_start_setup);
@@ -183,7 +177,7 @@ static unsigned long nr_blocks(struct file *file)
 	return i_size_read(inode) >> 10;
 }
 
-int __init rd_load_image(char *from)
+int __init rd_load_image(void)
 {
 	int res = 0;
 	unsigned long rd_blocks, devblocks, nr_disks;
@@ -197,7 +191,7 @@ int __init rd_load_image(char *from)
 	if (IS_ERR(out_file))
 		goto out;
 
-	in_file = filp_open(from, O_RDONLY, 0);
+	in_file = filp_open("/initrd.image", O_RDONLY, 0);
 	if (IS_ERR(in_file))
 		goto noclose_input;
 
@@ -226,10 +220,7 @@ int __init rd_load_image(char *from)
 	/*
 	 * OK, time to copy in the data
 	 */
-	if (strcmp(from, "/initrd.image") == 0)
-		devblocks = nblocks;
-	else
-		devblocks = nr_blocks(in_file);
+	devblocks = nblocks;
 
 	if (devblocks == 0) {
 		printk(KERN_ERR "RAMDISK: could not determine device size\n");
@@ -273,13 +264,6 @@ int __init rd_load_image(char *from)
 	return res;
 }
 
-int __init rd_load_disk(int n)
-{
-	create_dev("/dev/root", ROOT_DEV);
-	create_dev("/dev/ram", MKDEV(RAMDISK_MAJOR, n));
-	return rd_load_image("/dev/root");
-}
-
 static int exit_code;
 static int decompress_error;