[patch] unpacking early userspace onto tmpfs

tmpfs.diff (text/plain), 4.17 KB, created by Vlad on 2007-10-23 13:25:22 UTC

diff -ur linux-2.6.14.orig/fs/Kconfig linux-2.6.14/fs/Kconfig
--- linux-2.6.14.orig/fs/Kconfig	2005-09-11 03:19:07.000000000 +0000
+++ linux-2.6.14/fs/Kconfig	2005-09-11 03:19:42.000000000 +0000
@@ -805,6 +805,18 @@
 
 	  See <file:Documentation/filesystems/tmpfs.txt> for details.
 
+config EARLYUSERSPACE_ON_TMPFS
+	bool "Unpack the early userspace onto tmpfs"
+	depends TMPFS
+	default y
+	help
+	  Use this to have your early userspace placed (decompressed)
+	  onto tmpfs as opposed ramfs. This will allow you to
+	  restrict the size of your root-filesystem and it will also
+	  be swappable.
+   
+	  If unsure, say Y.
+
 config HUGETLBFS
 	bool "HugeTLB file system support"
 	depends X86 || IA64 || PPC64 || SPARC64 || SUPERH || X86_64 || BROKEN
Only in linux-2.6.14/fs: Kconfig.orig
diff -ur linux-2.6.14.orig/init/initramfs.c linux-2.6.14/init/initramfs.c
--- linux-2.6.14.orig/init/initramfs.c	2005-08-28 23:41:01.000000000 +0000
+++ linux-2.6.14/init/initramfs.c	2005-09-11 03:19:42.000000000 +0000
@@ -6,6 +6,7 @@
 #include <linux/delay.h>
 #include <linux/string.h>
 #include <linux/syscalls.h>
+#include <asm/uaccess.h>
 
 static __initdata char *message;
 static void __init error(char *x)
@@ -463,6 +464,49 @@
 	return message;
 }
 
+/* If we want the rootfs on initramfs so we mount initramfs over the
+ * rootfs before we unpack it. The little dance we do by creating a
+ * pivot point and moving the root to that is in fact necessary
+ * because lookups of "." don't resolve mountpoints.
+ */
+static inline void __init overmount_rootfs(void)
+   {
+#ifdef CONFIG_EARLYUSERSPACE_ON_TMPFS
+    int init_tmpfs(void);
+    int (*initfunc)(void) = init_tmpfs;
+    mm_segment_t oldfs;
+    char pivot[] = "/pivot";
+   
+    /* Explicitly go and init the overmount fs early (long-term
+     * the need for this will probably go away. */
+   
+    if (initfunc())
+    goto err;
+   
+    oldfs = get_fs();
+    set_fs(KERNEL_DS);
+   
+    if (sys_mkdir(pivot, 0700) < 0)
+    goto err;
+    if (sys_mount("tmpfs", pivot, "tmpfs", 0, "size=90%"))
+    goto err;
+   
+    /* Below here errors are unlikely and icky to deal with. */
+    sys_chdir(pivot);
+    sys_mount(".", "/", NULL, MS_MOVE, NULL);
+    sys_chdir(".");
+    sys_chroot(".");
+    printk(KERN_INFO "Overmounted tmpfs\n");
+    goto out;
+   
+    err:
+    printk(KERN_ERR "Overmount error\n");
+   
+    out:
+    set_fs(oldfs);
+#endif /* CONFIG_EARLYUSERSPACE_ON_TMPFS */
+}
+
 extern char __initramfs_start[], __initramfs_end[];
 #ifdef CONFIG_BLK_DEV_INITRD
 #include <linux/initrd.h>
@@ -482,6 +526,9 @@
 			initrd_end - initrd_start, 1);
 		if (!err) {
 			printk(" it is\n");
+#ifdef CONFIG_EARLYUSERSPACE_ON_TMPFS
+                        overmount_rootfs();
+#endif /* CONFIG_EARLYUSERSPACE_ON_TMPFS */
 			unpack_to_rootfs((char *)initrd_start,
 				initrd_end - initrd_start, 0);
 			free_initrd_mem(initrd_start, initrd_end);
diff -ur linux-2.6.14.orig/init/main.c linux-2.6.14/init/main.c
--- linux-2.6.14.orig/init/main.c	2005-09-11 03:19:07.000000000 +0000
+++ linux-2.6.14/init/main.c	2005-09-11 03:22:43.000000000 +0000
@@ -701,6 +701,11 @@
 	if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
 		ramdisk_execute_command = NULL;
 		prepare_namespace();
+#ifdef CONFIG_EARLYUSERSPACE_ON_TMPFS
+                int init_tmpfs(void);
+                int (*initfunc)(void) = init_tmpfs;
+                initfunc();
+#endif /* CONFIG_EARLYUSERSPACE_ON_TMPFS */
 	}
 
 	/*
diff -ur linux-2.6.14.orig/mm/shmem.c linux-2.6.14/mm/shmem.c
--- linux-2.6.14.orig/mm/shmem.c	2005-09-11 03:19:07.000000000 +0000
+++ linux-2.6.14/mm/shmem.c	2005-09-11 03:19:42.000000000 +0000
@@ -2136,7 +2136,7 @@
 };
 static struct vfsmount *shm_mnt;
 
-static int __init init_tmpfs(void)
+int __init init_tmpfs(void)
 {
 	int error;
 
@@ -2169,7 +2169,12 @@
 	shm_mnt = ERR_PTR(error);
 	return error;
 }
+/* Don't do this if we are calling it early explicity */
+#ifndef CONFIG_EARLYUSERSPACE_ON_TMPFS
+/* If CONFIG_EARLYUSERSPACE_ON_TMPFS is set then we will interpose
+ * ramfs so this will get called explicitly and early */
 module_init(init_tmpfs)
+#endif /* !CONFIG_EARLYUSERSPACE_ON_TMPFS */
 
 /*
  * shmem_file_setup - get an unlinked file living in tmpfs