[PATCH] drivers/block/initrd.c removal

From: viro@parcelfarce.linux.theplanet.co.uk

* drivers/block/initrd.c gone

* chunk of memory where the current tree would look for intird image is
  checked for being a valid initramfs image first; then, it is either
  unpacked (in addition to normal built-in image) or, if it wasn't a valid
  image, copied into a regular file on rootfs called /dev/initrd.  Then
  memory is freed.

Result:

a) we can put initramfs image in place of initrd one and kernel will DTRT.

b) initrd images still work as usual; code that shoves the thing to
   ramdisk, etc.  doesn't care whether it reads from a block device or
   regular file.

c) initrd.c is gone, so is fake block device and a lot of irregularities
   with it.

It has been in -mm for almost two weeks with no reported problems.

drivers/block/Makefile

@@ -28,7 +28,6 @@ obj-$(CONFIG_ATARI_ACSI)	+= acsi.o
 obj-$(CONFIG_ATARI_SLM)		+= acsi_slm.o
 obj-$(CONFIG_AMIGA_Z2RAM)	+= z2ram.o
 obj-$(CONFIG_BLK_DEV_RAM)	+= rd.o
-obj-$(CONFIG_BLK_DEV_INITRD)	+= initrd.o
 obj-$(CONFIG_BLK_DEV_LOOP)	+= loop.o
 obj-$(CONFIG_BLK_DEV_PS2)	+= ps2esdi.o
 obj-$(CONFIG_BLK_DEV_XD)	+= xd.o

drivers/block/initrd.c

-
-#include <linux/blkdev.h>
-#include <linux/genhd.h>
-#include <linux/initrd.h>
-#include <linux/init.h>
-#include <linux/major.h>
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <asm/uaccess.h>
-
-
-unsigned long initrd_start, initrd_end;
-int initrd_below_start_ok;
-
-static int initrd_users;
-static spinlock_t initrd_users_lock = SPIN_LOCK_UNLOCKED;
-
-static struct gendisk *initrd_disk;
-
-static ssize_t initrd_read(struct file *file, char *buf,
-			   size_t count, loff_t *ppos)
-{
-	int left = initrd_end - initrd_start - *ppos;
-
-	if (count > left)
-		count = left;
-	if (count == 0)
-		return 0;
-	if (copy_to_user(buf, (char *)initrd_start + *ppos, count))
-		return -EFAULT;
-
-	*ppos += count;
-	return count;
-}
-
-static int initrd_release(struct inode *inode,struct file *file)
-{
-
-	blkdev_put(inode->i_bdev, BDEV_FILE);
-
-	spin_lock(&initrd_users_lock);
-	if (!--initrd_users) {
-		spin_unlock(&initrd_users_lock);
-		del_gendisk(initrd_disk);
-		free_initrd_mem(initrd_start, initrd_end);
-		initrd_start = 0;
-	} else
-		spin_unlock(&initrd_users_lock);
-
-	return 0;
-}
-
-static struct file_operations initrd_fops = {
-	.read =		initrd_read,
-	.release =	initrd_release,
-};
-
-static int initrd_open(struct inode *inode, struct file *filp)
-{
-	if (!initrd_start) 
-		return -ENODEV;
-
-	spin_lock(&initrd_users_lock);
-	initrd_users++;
-	spin_unlock(&initrd_users_lock);
-
-	filp->f_op = &initrd_fops;
-	return 0;
-}
-
-static struct block_device_operations initrd_bdops = {
-	.owner =	THIS_MODULE,
-	.open =		initrd_open,
-};
-
-static int __init initrd_init(void)
-{
-	initrd_disk = alloc_disk(1);
-	if (!initrd_disk)
-		return -ENOMEM;
-
-	initrd_disk->major = RAMDISK_MAJOR;
-	initrd_disk->first_minor = INITRD_MINOR;
-	initrd_disk->fops = &initrd_bdops;	
-
-	sprintf(initrd_disk->disk_name, "initrd");
-	sprintf(initrd_disk->devfs_name, "rd/initrd");
-
-	set_capacity(initrd_disk, (initrd_end-initrd_start+511) >> 9);
-	add_disk(initrd_disk);
-	return 0;
-}
-
-static void __exit initrd_exit(void)
-{
-	put_disk(initrd_disk);
-}
-
-module_init(initrd_init);
-module_exit(initrd_exit);

init/do_mounts_initrd.c

@@ -9,6 +9,8 @@
 
 #include "do_mounts.h"
 
+unsigned long initrd_start, initrd_end;
+int initrd_below_start_ok;
 unsigned int real_root_dev;	/* do_proc_dointvec cannot handle kdev_t */
 static int __initdata old_fd, root_fd;
 static int __initdata mount_initrd = 1;
@@ -99,18 +101,20 @@ static void __init handle_initrd(void)
 
 int __init initrd_load(void)
 {
-	if (!mount_initrd)
-		return 0;
-
-	create_dev("/dev/ram", MKDEV(RAMDISK_MAJOR, 0), NULL);
-	create_dev("/dev/initrd", MKDEV(RAMDISK_MAJOR, INITRD_MINOR), NULL);
-	/* 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. */
-	if (rd_load_image("/dev/initrd") && ROOT_DEV != Root_RAM0) {
-		handle_initrd();
-		return 1;
+	if (mount_initrd) {
+		create_dev("/dev/ram", Root_RAM0, NULL);
+		/*
+		 * 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.
+		 */
+		if (rd_load_image("/dev/initrd") && ROOT_DEV != Root_RAM0) {
+			sys_unlink("/dev/initrd");
+			handle_initrd();
+			return 1;
+		}
 	}
+	sys_unlink("/dev/initrd");
 	return 0;
 }

init/initramfs.c

@@ -8,9 +8,11 @@
 #include <linux/delay.h>
 #include <linux/string.h>
 
+static __initdata char *message;
 static void __init error(char *x)
 {
-	panic("populate_root: %s\n", x);
+	if (!message)
+		message = x;
 }
 
 static void __init *malloc(int size)
@@ -63,7 +65,7 @@ static char __init *find_link(int major, int minor, int ino, char *name)
 	}
 	q = (struct hash *)malloc(sizeof(struct hash));
 	if (!q)
-		error("can't allocate link hash entry");
+		panic("can't allocate link hash entry");
 	q->ino = ino;
 	q->minor = minor;
 	q->major = major;
@@ -119,7 +121,7 @@ static void __init parse_header(char *s)
 
 /* FSM */
 
-enum state {
+static __initdata enum state {
 	Start,
 	Collect,
 	GotHeader,
@@ -130,9 +132,11 @@ enum state {
 	Reset
 } state, next_state;
 
-char *victim;
-unsigned count;
-loff_t this_header, next_header;
+static __initdata char *victim;
+static __initdata unsigned count;
+static __initdata loff_t this_header, next_header;
+
+static __initdata int dry_run;
 
 static inline void eat(unsigned n)
 {
@@ -185,23 +189,30 @@ static int __init do_collect(void)
 
 static int __init do_header(void)
 {
+	if (memcmp(collected, "070701", 6)) {
+		error("no cpio magic");
+		return 1;
+	}
 	parse_header(collected);
 	next_header = this_header + N_ALIGN(name_len) + body_len;
 	next_header = (next_header + 3) & ~3;
+	if (dry_run) {
+		read_into(name_buf, N_ALIGN(name_len), GotName);
+		return 0;
+	}
+	state = SkipIt;
 	if (name_len <= 0 || name_len > PATH_MAX)
-		state = SkipIt;
-	else if (S_ISLNK(mode)) {
+		return 0;
+	if (S_ISLNK(mode)) {
 		if (body_len > PATH_MAX)
-			state = SkipIt;
-		else {
-			collect = collected = symlink_buf;
-			remains = N_ALIGN(name_len) + body_len;
-			next_state = GotSymlink;
-			state = Collect;
-		}
-	} else if (body_len && !S_ISREG(mode))
-		state = SkipIt;
-	else
+			return 0;
+		collect = collected = symlink_buf;
+		remains = N_ALIGN(name_len) + body_len;
+		next_state = GotSymlink;
+		state = Collect;
+		return 0;
+	}
+	if (S_ISREG(mode) || !body_len)
 		read_into(name_buf, N_ALIGN(name_len), GotName);
 	return 0;
 }
@@ -248,6 +259,8 @@ static int __init do_name(void)
 		next_state = Reset;
 		return 0;
 	}
+	if (dry_run)
+		return 0;
 	if (S_ISREG(mode)) {
 		if (maybe_link() >= 0) {
 			wfd = sys_open(collected, O_WRONLY|O_CREAT, mode);
@@ -268,8 +281,7 @@ static int __init do_name(void)
 			sys_chown(collected, uid, gid);
 			sys_chmod(collected, mode);
 		}
-	} else
-		panic("populate_root: bogus mode: %o\n", mode);
+	}
 	return 0;
 }
 
@@ -323,13 +335,14 @@ static int __init write_buffer(char *buf, unsigned len)
 static void __init flush_buffer(char *buf, unsigned len)
 {
 	int written;
-	while ((written = write_buffer(buf, len)) < len) {
+	if (message)
+		return;
+	while ((written = write_buffer(buf, len)) < len && !message) {
 		char c = buf[written];
 		if (c == '0') {
 			buf += written;
 			len -= written;
 			state = Start;
-			continue;
 		} else
 			error("junk in compressed archive");
 	}
@@ -408,18 +421,20 @@ static void __init flush_window(void)
 	outcnt = 0;
 }
 
-static void __init unpack_to_rootfs(char *buf, unsigned len)
+char * __init unpack_to_rootfs(char *buf, unsigned len, int check_only)
 {
 	int written;
+	dry_run = check_only;
 	header_buf = malloc(110);
 	symlink_buf = malloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1);
 	name_buf = malloc(N_ALIGN(PATH_MAX));
 	window = malloc(WSIZE);
 	if (!window || !header_buf || !symlink_buf || !name_buf)
-		error("can't allocate buffers");
+		panic("can't allocate buffers");
 	state = Start;
 	this_header = 0;
-	while (len) {
+	message = NULL;
+	while (!message && len) {
 		loff_t saved_offset = this_header;
 		if (*buf == '0' && !(this_header & 3)) {
 			state = Start;
@@ -427,7 +442,8 @@ static void __init unpack_to_rootfs(char *buf, unsigned len)
 			buf += written;
 			len -= written;
 			continue;
-		} else if (!*buf) {
+		}
+		if (!*buf) {
 			buf++;
 			len--;
 			this_header++;
@@ -442,7 +458,7 @@ static void __init unpack_to_rootfs(char *buf, unsigned len)
 		crc = (ulg)0xffffffffL; /* shift register contents */
 		makecrc();
 		if (gunzip())
-			error("ungzip failed");
+			message = "ungzip failed";
 		if (state != Reset)
 			error("junk in gzipped archive");
 		this_header = saved_offset + inptr;
@@ -453,12 +469,41 @@ static void __init unpack_to_rootfs(char *buf, unsigned len)
 	free(name_buf);
 	free(symlink_buf);
 	free(header_buf);
+	return message;
 }
 
 extern char __initramfs_start, __initramfs_end;
+#ifdef CONFIG_BLK_DEV_INITRD
+#include <linux/initrd.h>
+#endif
 
 void __init populate_rootfs(void)
 {
-	unpack_to_rootfs(&__initramfs_start,
-			 &__initramfs_end - &__initramfs_start);
+	char *err = unpack_to_rootfs(&__initramfs_start,
+			 &__initramfs_end - &__initramfs_start, 0);
+	if (err)
+		panic(err);
+#ifdef CONFIG_BLK_DEV_INITRD
+	if (initrd_start) {
+		int fd;
+		printk(KERN_INFO "checking if image is initramfs...");
+		err = unpack_to_rootfs((char *)initrd_start,
+			initrd_end - initrd_start, 1);
+		if (!err) {
+			printk(" it is\n");
+			unpack_to_rootfs((char *)initrd_start,
+				initrd_end - initrd_start, 0);
+			free_initrd_mem(initrd_start, initrd_end);
+			return;
+		}
+		printk("it isn't (%s); looks like an initrd\n", err);
+		fd = sys_open("/dev/initrd", O_WRONLY|O_CREAT, 700);
+		if (fd >= 0) {
+			sys_write(fd, (char *)initrd_start,
+					initrd_end - initrd_start);
+			sys_close(fd);
+			free_initrd_mem(initrd_start, initrd_end);
+		}
+	}
+#endif
 }