[PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Askar Safin <safinaskar@gmail.com>]

Remove linuxrc initrd code path, which was deprecated in 2020.

Initramfs and (non-initial) RAM disks (i. e. brd) still work.

Both built-in and bootloader-supplied initramfs still work.

Non-linuxrc initrd code path (i. e. using /dev/ram as final root
filesystem) still works, but I put deprecation message into it

Signed-off-by: Askar Safin <safinaskar@gmail.com>
---
 .../admin-guide/kernel-parameters.txt         |  4 +-
 fs/init.c                                     | 14 ---
 include/linux/init_syscalls.h                 |  1 -
 include/linux/initrd.h                        |  2 -
 init/do_mounts.c                              |  4 +-
 init/do_mounts.h                              | 18 +---
 init/do_mounts_initrd.c                       | 85 ++-----------------
 init/do_mounts_rd.c                           | 17 +---
 8 files changed, 17 insertions(+), 128 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 521ab3425504..24d8899d8a39 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4285,7 +4285,7 @@
 			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
+	noinitrd	[Deprecated,RAM] Tells the kernel not to load any configured
 			initial RAM disk.
 
 	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
@@ -5299,7 +5299,7 @@
 	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
diff --git a/fs/init.c b/fs/init.c
index 07f592ccdba8..60719494d9a0 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -27,20 +27,6 @@ int __init init_mount(const char *dev_name, const char *dir_name,
 	return ret;
 }
 
-int __init init_umount(const char *name, int flags)
-{
-	int lookup_flags = LOOKUP_MOUNTPOINT;
-	struct path path;
-	int ret;
-
-	if (!(flags & UMOUNT_NOFOLLOW))
-		lookup_flags |= LOOKUP_FOLLOW;
-	ret = kern_path(name, lookup_flags, &path);
-	if (ret)
-		return ret;
-	return path_umount(&path, flags);
-}
-
 int __init init_chdir(const char *filename)
 {
 	struct path path;
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
index 92045d18cbfc..0bdbc458a881 100644
--- a/include/linux/init_syscalls.h
+++ b/include/linux/init_syscalls.h
@@ -2,7 +2,6 @@
 
 int __init init_mount(const char *dev_name, const char *dir_name,
 		const char *type_page, unsigned long flags, void *data_page);
-int __init init_umount(const char *name, int flags);
 int __init init_chdir(const char *filename);
 int __init init_chroot(const char *filename);
 int __init init_chown(const char *filename, uid_t user, gid_t group, int flags);
diff --git a/include/linux/initrd.h b/include/linux/initrd.h
index f1a1f4c92ded..7e5d26c8136f 100644
--- a/include/linux/initrd.h
+++ b/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;
 
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 0f2f44e6250c..1054ad3c905a 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -476,13 +476,11 @@ 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(".");
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 6069ea3eb80d..a386ee5314c9 100644
--- a/init/do_mounts.h
+++ b/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. */
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index f6867bad0d78..d4f5f4c60a22 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -2,13 +2,7 @@
 #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"
 
@@ -41,6 +35,7 @@ late_initcall(kernel_do_mounts_initrd_sysctls_init);
 
 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 +65,17 @@ 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 September 2026; "
+				"use initramfs instead or (as a last resort) /sys/firmware/initrd.\n");
 		}
 	}
 	init_unlink("/initrd.image");
-	return false;
 }
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 5311f2d7edc8..0a021bbcd501 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -22,6 +22,7 @@ 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");
 	rd_image_start = simple_strtol(str,NULL,0);
 	return 1;
 }
@@ -177,7 +178,7 @@ 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;
@@ -191,7 +192,7 @@ 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;
 
@@ -220,10 +221,7 @@ 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");
@@ -267,13 +265,6 @@ 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;
 
-- 
2.47.3