4 files changed, 777 insertions, 0 deletions

diff --git a/fs/cramfs/Makefile b/fs/cramfs/Makefile
new file mode 100644
index 000000000000..92ebb464a725
--- /dev/null
+++ b/fs/cramfs/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for the linux cramfs routines.
+#
+
+obj-$(CONFIG_CRAMFS) += cramfs.o
+
+cramfs-objs := inode.o uncompress.o
diff --git a/fs/cramfs/README b/fs/cramfs/README
new file mode 100644
index 000000000000..445d1c2d7646
--- /dev/null
+++ b/fs/cramfs/README
@@ -0,0 +1,168 @@
+Notes on Filesystem Layout
+--------------------------
+
+These notes describe what mkcramfs generates.  Kernel requirements are
+a bit looser, e.g. it doesn't care if the <file_data> items are
+swapped around (though it does care that directory entries (inodes) in
+a given directory are contiguous, as this is used by readdir).
+
+All data is currently in host-endian format; neither mkcramfs nor the
+kernel ever do swabbing.  (See section `Block Size' below.)
+
+<filesystem>:
+        <superblock>
+        <directory_structure>
+        <data>
+
+<superblock>: struct cramfs_super (see cramfs_fs.h).
+
+<directory_structure>:
+        For each file:
+                struct cramfs_inode (see cramfs_fs.h).
+                Filename.  Not generally null-terminated, but it is
+                 null-padded to a multiple of 4 bytes.
+
+The order of inode traversal is described as "width-first" (not to be
+confused with breadth-first); i.e. like depth-first but listing all of
+a directory's entries before recursing down its subdirectories: the
+same order as `ls -AUR' (but without the /^\..*:$/ directory header
+lines); put another way, the same order as `find -type d -exec
+ls -AU1 {} \;'.
+
+Beginning in 2.4.7, directory entries are sorted.  This optimization
+allows cramfs_lookup to return more quickly when a filename does not
+exist, speeds up user-space directory sorts, etc.
+
+<data>:
+        One <file_data> for each file that's either a symlink or a
+         regular file of non-zero st_size.
+
+<file_data>:
+        nblocks * <block_pointer>
+         (where nblocks = (st_size - 1) / blksize + 1)
+        nblocks * <block>
+        padding to multiple of 4 bytes
+
+The i'th <block_pointer> for a file stores the byte offset of the
+*end* of the i'th <block> (i.e. one past the last byte, which is the
+same as the start of the (i+1)'th <block> if there is one).  The first
+<block> immediately follows the last <block_pointer> for the file.
+<block_pointer>s are each 32 bits long.
+
+The order of <file_data>'s is a depth-first descent of the directory
+tree, i.e. the same order as `find -size +0 \( -type f -o -type l \)
+-print'.
+
+
+<block>: The i'th <block> is the output of zlib's compress function
+applied to the i'th blksize-sized chunk of the input data.
+(For the last <block> of the file, the input may of course be smaller.)
+Each <block> may be a different size.  (See <block_pointer> above.)
+<block>s are merely byte-aligned, not generally u32-aligned.
+
+
+Holes
+-----
+
+This kernel supports cramfs holes (i.e. [efficient representation of]
+blocks in uncompressed data consisting entirely of NUL bytes), but by
+default mkcramfs doesn't test for & create holes, since cramfs in
+kernels up to at least 2.3.39 didn't support holes.  Run mkcramfs
+with -z if you want it to create files that can have holes in them.
+
+
+Tools
+-----
+
+The cramfs user-space tools, including mkcramfs and cramfsck, are
+located at <http://sourceforge.net/projects/cramfs/>.
+
+
+Future Development
+==================
+
+Block Size
+----------
+
+(Block size in cramfs refers to the size of input data that is
+compressed at a time.  It's intended to be somewhere around
+PAGE_CACHE_SIZE for cramfs_readpage's convenience.)
+
+The superblock ought to indicate the block size that the fs was
+written for, since comments in <linux/pagemap.h> indicate that
+PAGE_CACHE_SIZE may grow in future (if I interpret the comment
+correctly).
+
+Currently, mkcramfs #define's PAGE_CACHE_SIZE as 4096 and uses that
+for blksize, whereas Linux-2.3.39 uses its PAGE_CACHE_SIZE, which in
+turn is defined as PAGE_SIZE (which can be as large as 32KB on arm).
+This discrepancy is a bug, though it's not clear which should be
+changed.
+
+One option is to change mkcramfs to take its PAGE_CACHE_SIZE from
+<asm/page.h>.  Personally I don't like this option, but it does
+require the least amount of change: just change `#define
+PAGE_CACHE_SIZE (4096)' to `#include <asm/page.h>'.  The disadvantage
+is that the generated cramfs cannot always be shared between different
+kernels, not even necessarily kernels of the same architecture if
+PAGE_CACHE_SIZE is subject to change between kernel versions
+(currently possible with arm and ia64).
+
+The remaining options try to make cramfs more sharable.
+
+One part of that is addressing endianness.  The two options here are
+`always use little-endian' (like ext2fs) or `writer chooses
+endianness; kernel adapts at runtime'.  Little-endian wins because of
+code simplicity and little CPU overhead even on big-endian machines.
+
+The cost of swabbing is changing the code to use the le32_to_cpu
+etc. macros as used by ext2fs.  We don't need to swab the compressed
+data, only the superblock, inodes and block pointers.
+
+
+The other part of making cramfs more sharable is choosing a block
+size.  The options are:
+
+  1. Always 4096 bytes.
+
+  2. Writer chooses blocksize; kernel adapts but rejects blocksize >
+     PAGE_CACHE_SIZE.
+
+  3. Writer chooses blocksize; kernel adapts even to blocksize >
+     PAGE_CACHE_SIZE.
+
+It's easy enough to change the kernel to use a smaller value than
+PAGE_CACHE_SIZE: just make cramfs_readpage read multiple blocks.
+
+The cost of option 1 is that kernels with a larger PAGE_CACHE_SIZE
+value don't get as good compression as they can.
+
+The cost of option 2 relative to option 1 is that the code uses
+variables instead of #define'd constants.  The gain is that people
+with kernels having larger PAGE_CACHE_SIZE can make use of that if
+they don't mind their cramfs being inaccessible to kernels with
+smaller PAGE_CACHE_SIZE values.
+
+Option 3 is easy to implement if we don't mind being CPU-inefficient:
+e.g. get readpage to decompress to a buffer of size MAX_BLKSIZE (which
+must be no larger than 32KB) and discard what it doesn't need.
+Getting readpage to read into all the covered pages is harder.
+
+The main advantage of option 3 over 1, 2, is better compression.  The
+cost is greater complexity.  Probably not worth it, but I hope someone
+will disagree.  (If it is implemented, then I'll re-use that code in
+e2compr.)
+
+
+Another cost of 2 and 3 over 1 is making mkcramfs use a different
+block size, but that just means adding and parsing a -b option.
+
+
+Inode Size
+----------
+
+Given that cramfs will probably be used for CDs etc. as well as just
+silicon ROMs, it might make sense to expand the inode a little from
+its current 12 bytes.  Inodes other than the root inode are followed
+by filename, so the expansion doesn't even have to be a multiple of 4
+bytes.
diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
new file mode 100644
index 000000000000..6c285efa2004
--- /dev/null
+++ b/fs/cramfs/inode.c
@@ -0,0 +1,525 @@
+/*
+ * Compressed rom filesystem for Linux.
+ *
+ * Copyright (C) 1999 Linus Torvalds.
+ *
+ * This file is released under the GPL.
+ */
+
+/*
+ * These are the VFS interfaces to the compressed rom filesystem.
+ * The actual compression is based on zlib, see the other files.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/blkdev.h>
+#include <linux/cramfs_fs.h>
+#include <linux/slab.h>
+#include <linux/cramfs_fs_sb.h>
+#include <linux/buffer_head.h>
+#include <linux/vfs.h>
+#include <asm/semaphore.h>
+
+#include <asm/uaccess.h>
+
+static struct super_operations cramfs_ops;
+static struct inode_operations cramfs_dir_inode_operations;
+static struct file_operations cramfs_directory_operations;
+static struct address_space_operations cramfs_aops;
+
+static DECLARE_MUTEX(read_mutex);
+
+
+/* These two macros may change in future, to provide better st_ino
+   semantics. */
+#define CRAMINO(x)      ((x)->offset?(x)->offset<<2:1)
+#define OFFSET(x)       ((x)->i_ino)
+
+static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inode * cramfs_inode)
+{
+        struct inode * inode = new_inode(sb);
+        static struct timespec zerotime;
+
+        if (inode) {
+                inode->i_mode = cramfs_inode->mode;
+                inode->i_uid = cramfs_inode->uid;
+                inode->i_size = cramfs_inode->size;
+                inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
+                inode->i_blksize = PAGE_CACHE_SIZE;
+                inode->i_gid = cramfs_inode->gid;
+                /* Struct copy intentional */
+                inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
+                inode->i_ino = CRAMINO(cramfs_inode);
+                /* inode->i_nlink is left 1 - arguably wrong for directories,
+                   but it's the best we can do without reading the directory
+                   contents.  1 yields the right result in GNU find, even
+                   without -noleaf option. */
+                insert_inode_hash(inode);
+                if (S_ISREG(inode->i_mode)) {
+                        inode->i_fop = &generic_ro_fops;
+                        inode->i_data.a_ops = &cramfs_aops;
+                } else if (S_ISDIR(inode->i_mode)) {
+                        inode->i_op = &cramfs_dir_inode_operations;
+                        inode->i_fop = &cramfs_directory_operations;
+                } else if (S_ISLNK(inode->i_mode)) {
+                        inode->i_op = &page_symlink_inode_operations;
+                        inode->i_data.a_ops = &cramfs_aops;
+                } else {
+                        inode->i_size = 0;
+                        inode->i_blocks = 0;
+                        init_special_inode(inode, inode->i_mode,
+                                old_decode_dev(cramfs_inode->size));
+                }
+        }
+        return inode;
+}
+
+/*
+ * We have our own block cache: don't fill up the buffer cache
+ * with the rom-image, because the way the filesystem is set
+ * up the accesses should be fairly regular and cached in the
+ * page cache and dentry tree anyway..
+ *
+ * This also acts as a way to guarantee contiguous areas of up to
+ * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
+ * worry about end-of-buffer issues even when decompressing a full
+ * page cache.
+ */
+#define READ_BUFFERS (2)
+/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
+#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
+
+/*
+ * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
+ * data that takes up more space than the original and with unlucky
+ * alignment.
+ */
+#define BLKS_PER_BUF_SHIFT      (2)
+#define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
+#define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
+
+static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
+static unsigned buffer_blocknr[READ_BUFFERS];
+static struct super_block * buffer_dev[READ_BUFFERS];
+static int next_buffer;
+
+/*
+ * Returns a pointer to a buffer containing at least LEN bytes of
+ * filesystem starting at byte offset OFFSET into the filesystem.
+ */
+static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
+{
+        struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
+        struct page *pages[BLKS_PER_BUF];
+        unsigned i, blocknr, buffer, unread;
+        unsigned long devsize;
+        char *data;
+
+        if (!len)
+                return NULL;
+        blocknr = offset >> PAGE_CACHE_SHIFT;
+        offset &= PAGE_CACHE_SIZE - 1;
+
+        /* Check if an existing buffer already has the data.. */
+        for (i = 0; i < READ_BUFFERS; i++) {
+                unsigned int blk_offset;
+
+                if (buffer_dev[i] != sb)
+                        continue;
+                if (blocknr < buffer_blocknr[i])
+                        continue;
+                blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
+                blk_offset += offset;
+                if (blk_offset + len > BUFFER_SIZE)
+                        continue;
+                return read_buffers[i] + blk_offset;
+        }
+
+        devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
+
+        /* Ok, read in BLKS_PER_BUF pages completely first. */
+        unread = 0;
+        for (i = 0; i < BLKS_PER_BUF; i++) {
+                struct page *page = NULL;
+
+                if (blocknr + i < devsize) {
+                        page = read_cache_page(mapping, blocknr + i,
+                                (filler_t *)mapping->a_ops->readpage,
+                                NULL);
+                        /* synchronous error? */
+                        if (IS_ERR(page))
+                                page = NULL;
+                }
+                pages[i] = page;
+        }
+
+        for (i = 0; i < BLKS_PER_BUF; i++) {
+                struct page *page = pages[i];
+                if (page) {
+                        wait_on_page_locked(page);
+                        if (!PageUptodate(page)) {
+                                /* asynchronous error */
+                                page_cache_release(page);
+                                pages[i] = NULL;
+                        }
+                }
+        }
+
+        buffer = next_buffer;
+        next_buffer = NEXT_BUFFER(buffer);
+        buffer_blocknr[buffer] = blocknr;
+        buffer_dev[buffer] = sb;
+
+        data = read_buffers[buffer];
+        for (i = 0; i < BLKS_PER_BUF; i++) {
+                struct page *page = pages[i];
+                if (page) {
+                        memcpy(data, kmap(page), PAGE_CACHE_SIZE);
+                        kunmap(page);
+                        page_cache_release(page);
+                } else
+                        memset(data, 0, PAGE_CACHE_SIZE);
+                data += PAGE_CACHE_SIZE;
+        }
+        return read_buffers[buffer] + offset;
+}
+
+static void cramfs_put_super(struct super_block *sb)
+{
+        kfree(sb->s_fs_info);
+        sb->s_fs_info = NULL;
+}
+
+static int cramfs_remount(struct super_block *sb, int *flags, char *data)
+{
+        *flags |= MS_RDONLY;
+        return 0;
+}
+
+static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+        int i;
+        struct cramfs_super super;
+        unsigned long root_offset;
+        struct cramfs_sb_info *sbi;
+        struct inode *root;
+
+        sb->s_flags |= MS_RDONLY;
+
+        sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
+        if (!sbi)
+                return -ENOMEM;
+        sb->s_fs_info = sbi;
+        memset(sbi, 0, sizeof(struct cramfs_sb_info));
+
+        /* Invalidate the read buffers on mount: think disk change.. */
+        down(&read_mutex);
+        for (i = 0; i < READ_BUFFERS; i++)
+                buffer_blocknr[i] = -1;
+
+        /* Read the first block and get the superblock from it */
+        memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
+        up(&read_mutex);
+
+        /* Do sanity checks on the superblock */
+        if (super.magic != CRAMFS_MAGIC) {
+                /* check at 512 byte offset */
+                down(&read_mutex);
+                memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
+                up(&read_mutex);
+                if (super.magic != CRAMFS_MAGIC) {
+                        if (!silent)
+                                printk(KERN_ERR "cramfs: wrong magic\n");
+                        goto out;
+                }
+        }
+
+        /* get feature flags first */
+        if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
+                printk(KERN_ERR "cramfs: unsupported filesystem features\n");
+                goto out;
+        }
+
+        /* Check that the root inode is in a sane state */
+        if (!S_ISDIR(super.root.mode)) {
+                printk(KERN_ERR "cramfs: root is not a directory\n");
+                goto out;
+        }
+        root_offset = super.root.offset << 2;
+        if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
+                sbi->size=super.size;
+                sbi->blocks=super.fsid.blocks;
+                sbi->files=super.fsid.files;
+        } else {
+                sbi->size=1<<28;
+                sbi->blocks=0;
+                sbi->files=0;
+        }
+        sbi->magic=super.magic;
+        sbi->flags=super.flags;
+        if (root_offset == 0)
+                printk(KERN_INFO "cramfs: empty filesystem");
+        else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
+                 ((root_offset != sizeof(struct cramfs_super)) &&
+                  (root_offset != 512 + sizeof(struct cramfs_super))))
+        {
+                printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
+                goto out;
+        }
+
+        /* Set it all up.. */
+        sb->s_op = &cramfs_ops;
+        root = get_cramfs_inode(sb, &super.root);
+        if (!root)
+                goto out;
+        sb->s_root = d_alloc_root(root);
+        if (!sb->s_root) {
+                iput(root);
+                goto out;
+        }
+        return 0;
+out:
+        kfree(sbi);
+        sb->s_fs_info = NULL;
+        return -EINVAL;
+}
+
+static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf)
+{
+        buf->f_type = CRAMFS_MAGIC;
+        buf->f_bsize = PAGE_CACHE_SIZE;
+        buf->f_blocks = CRAMFS_SB(sb)->blocks;
+        buf->f_bfree = 0;
+        buf->f_bavail = 0;
+        buf->f_files = CRAMFS_SB(sb)->files;
+        buf->f_ffree = 0;
+        buf->f_namelen = CRAMFS_MAXPATHLEN;
+        return 0;
+}
+
+/*
+ * Read a cramfs directory entry.
+ */
+static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
+{
+        struct inode *inode = filp->f_dentry->d_inode;
+        struct super_block *sb = inode->i_sb;
+        char *buf;
+        unsigned int offset;
+        int copied;
+
+        /* Offset within the thing. */
+        offset = filp->f_pos;
+        if (offset >= inode->i_size)
+                return 0;
+        /* Directory entries are always 4-byte aligned */
+        if (offset & 3)
+                return -EINVAL;
+
+        buf = kmalloc(256, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+
+        copied = 0;
+        while (offset < inode->i_size) {
+                struct cramfs_inode *de;
+                unsigned long nextoffset;
+                char *name;
+                ino_t ino;
+                mode_t mode;
+                int namelen, error;
+
+                down(&read_mutex);
+                de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
+                name = (char *)(de+1);
+
+                /*
+                 * Namelengths on disk are shifted by two
+                 * and the name padded out to 4-byte boundaries
+                 * with zeroes.
+                 */
+                namelen = de->namelen << 2;
+                memcpy(buf, name, namelen);
+                ino = CRAMINO(de);
+                mode = de->mode;
+                up(&read_mutex);
+                nextoffset = offset + sizeof(*de) + namelen;
+                for (;;) {
+                        if (!namelen) {
+                                kfree(buf);
+                                return -EIO;
+                        }
+                        if (buf[namelen-1])
+                                break;
+                        namelen--;
+                }
+                error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
+                if (error)
+                        break;
+
+                offset = nextoffset;
+                filp->f_pos = offset;
+                copied++;
+        }
+        kfree(buf);
+        return 0;
+}
+
+/*
+ * Lookup and fill in the inode data..
+ */
+static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
+{
+        unsigned int offset = 0;
+        int sorted;
+
+        down(&read_mutex);
+        sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
+        while (offset < dir->i_size) {
+                struct cramfs_inode *de;
+                char *name;
+                int namelen, retval;
+
+                de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
+                name = (char *)(de+1);
+
+                /* Try to take advantage of sorted directories */
+                if (sorted && (dentry->d_name.name[0] < name[0]))
+                        break;
+
+                namelen = de->namelen << 2;
+                offset += sizeof(*de) + namelen;
+
+                /* Quick check that the name is roughly the right length */
+                if (((dentry->d_name.len + 3) & ~3) != namelen)
+                        continue;
+
+                for (;;) {
+                        if (!namelen) {
+                                up(&read_mutex);
+                                return ERR_PTR(-EIO);
+                        }
+                        if (name[namelen-1])
+                                break;
+                        namelen--;
+                }
+                if (namelen != dentry->d_name.len)
+                        continue;
+                retval = memcmp(dentry->d_name.name, name, namelen);
+                if (retval > 0)
+                        continue;
+                if (!retval) {
+                        struct cramfs_inode entry = *de;
+                        up(&read_mutex);
+                        d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
+                        return NULL;
+                }
+                /* else (retval < 0) */
+                if (sorted)
+                        break;
+        }
+        up(&read_mutex);
+        d_add(dentry, NULL);
+        return NULL;
+}
+
+static int cramfs_readpage(struct file *file, struct page * page)
+{
+        struct inode *inode = page->mapping->host;
+        u32 maxblock, bytes_filled;
+        void *pgdata;
+
+        maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+        bytes_filled = 0;
+        if (page->index < maxblock) {
+                struct super_block *sb = inode->i_sb;
+                u32 blkptr_offset = OFFSET(inode) + page->index*4;
+                u32 start_offset, compr_len;
+
+                start_offset = OFFSET(inode) + maxblock*4;
+                down(&read_mutex);
+                if (page->index)
+                        start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
+                compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
+                up(&read_mutex);
+                pgdata = kmap(page);
+                if (compr_len == 0)
+                        ; /* hole */
+                else {
+                        down(&read_mutex);
+                        bytes_filled = cramfs_uncompress_block(pgdata,
+                                 PAGE_CACHE_SIZE,
+                                 cramfs_read(sb, start_offset, compr_len),
+                                 compr_len);
+                        up(&read_mutex);
+                }
+        } else
+                pgdata = kmap(page);
+        memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
+        kunmap(page);
+        flush_dcache_page(page);
+        SetPageUptodate(page);
+        unlock_page(page);
+        return 0;
+}
+
+static struct address_space_operations cramfs_aops = {
+        .readpage = cramfs_readpage
+};
+
+/*
+ * Our operations:
+ */
+
+/*
+ * A directory can only readdir
+ */
+static struct file_operations cramfs_directory_operations = {
+        .llseek         = generic_file_llseek,
+        .read           = generic_read_dir,
+        .readdir        = cramfs_readdir,
+};
+
+static struct inode_operations cramfs_dir_inode_operations = {
+        .lookup         = cramfs_lookup,
+};
+
+static struct super_operations cramfs_ops = {
+        .put_super      = cramfs_put_super,
+        .remount_fs     = cramfs_remount,
+        .statfs         = cramfs_statfs,
+};
+
+static struct super_block *cramfs_get_sb(struct file_system_type *fs_type,
+        int flags, const char *dev_name, void *data)
+{
+        return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
+}
+
+static struct file_system_type cramfs_fs_type = {
+        .owner          = THIS_MODULE,
+        .name           = "cramfs",
+        .get_sb         = cramfs_get_sb,
+        .kill_sb        = kill_block_super,
+        .fs_flags       = FS_REQUIRES_DEV,
+};
+
+static int __init init_cramfs_fs(void)
+{
+        cramfs_uncompress_init();
+        return register_filesystem(&cramfs_fs_type);
+}
+
+static void __exit exit_cramfs_fs(void)
+{
+        cramfs_uncompress_exit();
+        unregister_filesystem(&cramfs_fs_type);
+}
+
+module_init(init_cramfs_fs)
+module_exit(exit_cramfs_fs)
+MODULE_LICENSE("GPL");
diff --git a/fs/cramfs/uncompress.c b/fs/cramfs/uncompress.c
new file mode 100644
index 000000000000..5034365b06a8
--- /dev/null
+++ b/fs/cramfs/uncompress.c
@@ -0,0 +1,77 @@
+/*
+ * uncompress.c
+ *
+ * (C) Copyright 1999 Linus Torvalds
+ *
+ * cramfs interfaces to the uncompression library. There's really just
+ * three entrypoints:
+ *
+ *  - cramfs_uncompress_init() - called to initialize the thing.
+ *  - cramfs_uncompress_exit() - tell me when you're done
+ *  - cramfs_uncompress_block() - uncompress a block.
+ *
+ * NOTE NOTE NOTE! The uncompression is entirely single-threaded. We
+ * only have one stream, and we'll initialize it only once even if it
+ * then is used by multiple filesystems.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/vmalloc.h>
+#include <linux/zlib.h>
+
+static z_stream stream;
+static int initialized;
+
+/* Returns length of decompressed data. */
+int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
+{
+        int err;
+
+        stream.next_in = src;
+        stream.avail_in = srclen;
+
+        stream.next_out = dst;
+        stream.avail_out = dstlen;
+
+        err = zlib_inflateReset(&stream);
+        if (err != Z_OK) {
+                printk("zlib_inflateReset error %d\n", err);
+                zlib_inflateEnd(&stream);
+                zlib_inflateInit(&stream);
+        }
+
+        err = zlib_inflate(&stream, Z_FINISH);
+        if (err != Z_STREAM_END)
+                goto err;
+        return stream.total_out;
+
+err:
+        printk("Error %d while decompressing!\n", err);
+        printk("%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
+        return 0;
+}
+
+int cramfs_uncompress_init(void)
+{
+        if (!initialized++) {
+                stream.workspace = vmalloc(zlib_inflate_workspacesize());
+                if ( !stream.workspace ) {
+                        initialized = 0;
+                        return -ENOMEM;
+                }
+                stream.next_in = NULL;
+                stream.avail_in = 0;
+                zlib_inflateInit(&stream);
+        }
+        return 0;
+}
+
+int cramfs_uncompress_exit(void)
+{
+        if (!--initialized) {
+                zlib_inflateEnd(&stream);
+                vfree(stream.workspace);
+        }
+        return 0;
+}