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/*

 * 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 <linux/mutex.h>

#include <asm/semaphore.h>

#include <asm/uaccess.h>

static const struct super_operations cramfs_ops;

static const struct inode_operations cramfs_dir_inode_operations;

static const struct file_operations cramfs_directory_operations;

static const struct address_space_operations cramfs_aops;

static DEFINE_MUTEX(read_mutex);

/* These two macros may change in future, to provide better st_ino

   semantics. */

#define CRAMINO(x)      (((x)->offset && (x)->size)?(x)->offset<<2:1)

#define OFFSET(x)       ((x)->i_ino)

static int cramfs_iget5_test(struct inode *inode, void *opaque)

{

        struct cramfs_inode *cramfs_inode = opaque;

        if (inode->i_ino != CRAMINO(cramfs_inode))

                return 0; /* does not match */

        if (inode->i_ino != 1)

                return 1;

        /* all empty directories, char, block, pipe, and sock, share inode #1 */

        if ((inode->i_mode != cramfs_inode->mode) ||

            (inode->i_gid != cramfs_inode->gid) ||

            (inode->i_uid != cramfs_inode->uid))

                return 0; /* does not match */

        if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&

            (inode->i_rdev != old_decode_dev(cramfs_inode->size)))

                return 0; /* does not match */

        return 1; /* matches */

}

static int cramfs_iget5_set(struct inode *inode, void *opaque)

{

        static struct timespec zerotime;

        struct cramfs_inode *cramfs_inode = opaque;

        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_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. */

        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 0;

}

static struct inode *get_cramfs_inode(struct super_block *sb,

                                struct cramfs_inode * cramfs_inode)

{

        struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),

                                            cramfs_iget5_test, cramfs_iget5_set,

                                            cramfs_inode);

        if (inode && (inode->i_state & I_NEW)) {

                unlock_new_inode(inode);

        }

        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;

        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. */

        for (i = 0; i < BLKS_PER_BUF; i++) {

                struct page *page = NULL;

                if (blocknr + i < devsize) {

                        page = read_mapping_page_async(mapping, blocknr + i,

                                                                        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 = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);

        if (!sbi)

                return -ENOMEM;

        sb->s_fs_info = sbi;

        /* Invalidate the read buffers on mount: think disk change.. */

        mutex_lock(&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));

        mutex_unlock(&read_mutex);

        /* Do sanity checks on the superblock */

        if (super.magic != CRAMFS_MAGIC) {

                /* check for wrong endianess */

                if (super.magic == CRAMFS_MAGIC_WEND) {

                        if (!silent)

                                printk(KERN_ERR "cramfs: wrong endianess\n");

                        goto out;

                }

                /* check at 512 byte offset */

                mutex_lock(&read_mutex);

                memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));

                mutex_unlock(&read_mutex);

                if (super.magic != CRAMFS_MAGIC) {

                        if (super.magic == CRAMFS_MAGIC_WEND && !silent)

                                printk(KERN_ERR "cramfs: wrong endianess\n");

                        else 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 dentry *dentry, struct kstatfs *buf)

{

        struct super_block *sb = dentry->d_sb;

        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_path.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(CRAMFS_MAXPATHLEN, 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;

                mutex_lock(&read_mutex);

                de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);

                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;

                mutex_unlock(&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;

        mutex_lock(&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)+CRAMFS_MAXPATHLEN);

                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) {

                                mutex_unlock(&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;

                        mutex_unlock(&read_mutex);

                        d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));

                        return NULL;

                }

                /* else (retval < 0) */

                if (sorted)

                        break;

        }

        mutex_unlock(&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;

                mutex_lock(&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);

                mutex_unlock(&read_mutex);

                pgdata = kmap(page);

                if (compr_len == 0)

                        ; /* hole */

                else if (compr_len > (PAGE_CACHE_SIZE << 1))

                        printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);

                else {

                        mutex_lock(&read_mutex);

                        bytes_filled = cramfs_uncompress_block(pgdata,

                                 PAGE_CACHE_SIZE,

                                 cramfs_read(sb, start_offset, compr_len),

                                 compr_len);

                        mutex_unlock(&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 const struct address_space_operations cramfs_aops = {

        .readpage = cramfs_readpage

};

/*

 * Our operations:

 */

/*

 * A directory can only readdir

 */

static const struct file_operations cramfs_directory_operations = {

        .llseek         = generic_file_llseek,

        .read           = generic_read_dir,

        .readdir        = cramfs_readdir,

};

static const struct inode_operations cramfs_dir_inode_operations = {

        .lookup         = cramfs_lookup,

};

static const struct super_operations cramfs_ops = {

        .put_super      = cramfs_put_super,

        .remount_fs     = cramfs_remount,

        .statfs         = cramfs_statfs,

};

static int cramfs_get_sb(struct file_system_type *fs_type,

        int flags, const char *dev_name, void *data, struct vfsmount *mnt)

{

        return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,

                           mnt);

}

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)

{

        int rv;

        rv = cramfs_uncompress_init();

        if (rv < 0)

                return rv;

        rv = register_filesystem(&cramfs_fs_type);

        if (rv < 0)

                cramfs_uncompress_exit();

        return rv;

}

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");