Inspired by the situation from [0]. The roots of choosing tmpfs/ramfs backend for rootfs go far back in history, and it's unclear at all why it was decided to select full-blown tmpfs when "root=" is not specified and feature-poor ramfs otherwise. There are several cases when "root=" is not needed at all to work, and it doesn't break anything or make any [negative] sense. On the other hand, such separation is rather counter-intuitive and makes debugging more difficult. Simply always use tmpfs when it's available -- just like devtmpfs does [for over a decade]. [0] https://lore.kernel.org/kernel-hardening/20210701234807.50453-1-alobakin@xxxxx/ Signed-off-by: Alexander Lobakin <alobakin@xxxxx> --- fs/namespace.c | 2 -- include/linux/init.h | 1 - init/do_mounts.c | 26 +++++++------------------- 3 files changed, 7 insertions(+), 22 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index ab4174a3c802..310ab44fdbe7 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -17,7 +17,6 @@ #include <linux/security.h> #include <linux/cred.h> #include <linux/idr.h> -#include <linux/init.h> /* init_rootfs */ #include <linux/fs_struct.h> /* get_fs_root et.al. */ #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ #include <linux/file.h> @@ -4248,7 +4247,6 @@ void __init mnt_init(void) if (!fs_kobj) printk(KERN_WARNING "%s: kobj create error\n", __func__); shmem_init(); - init_rootfs(); init_mount_tree(); } diff --git a/include/linux/init.h b/include/linux/init.h index d82b4b2e1d25..10839922a1d3 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -148,7 +148,6 @@ extern unsigned int reset_devices; /* used by init/main.c */ void setup_arch(char **); void prepare_namespace(void); -void __init init_rootfs(void); extern struct file_system_type rootfs_fs_type; #if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX) diff --git a/init/do_mounts.c b/init/do_mounts.c index 74aede860de7..c00b05015a66 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -611,24 +611,12 @@ void __init prepare_namespace(void) init_chroot("."); } -static bool is_tmpfs; -static int rootfs_init_fs_context(struct fs_context *fc) -{ - if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs) - return shmem_init_fs_context(fc); - - return ramfs_init_fs_context(fc); -} - struct file_system_type rootfs_fs_type = { - .name = "rootfs", - .init_fs_context = rootfs_init_fs_context, - .kill_sb = kill_litter_super, + .name = "rootfs", +#ifdef CONFIG_TMPFS + .init_fs_context = shmem_init_fs_context, +#else + .init_fs_context = ramfs_init_fs_context, +#endif + .kill_sb = kill_litter_super, }; - -void __init init_rootfs(void) -{ - if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && - (!root_fs_names || strstr(root_fs_names, "tmpfs"))) - is_tmpfs = true; -} -- 2.32.0
