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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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612 lines
14 KiB
C
612 lines
14 KiB
C
/*
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* Compressed rom filesystem for Linux.
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*
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* Copyright (C) 1999 Linus Torvalds.
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*
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* This file is released under the GPL.
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*/
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/*
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* These are the VFS interfaces to the compressed rom filesystem.
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* The actual compression is based on zlib, see the other files.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/string.h>
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#include <linux/blkdev.h>
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#include <linux/slab.h>
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#include <linux/vfs.h>
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#include <linux/mutex.h>
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#include <uapi/linux/cramfs_fs.h>
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#include <linux/uaccess.h>
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#include "internal.h"
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/*
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* cramfs super-block data in memory
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*/
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struct cramfs_sb_info {
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unsigned long magic;
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unsigned long size;
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unsigned long blocks;
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unsigned long files;
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unsigned long flags;
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};
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static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
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{
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return sb->s_fs_info;
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}
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static const struct super_operations cramfs_ops;
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static const struct inode_operations cramfs_dir_inode_operations;
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static const struct file_operations cramfs_directory_operations;
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static const struct address_space_operations cramfs_aops;
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static DEFINE_MUTEX(read_mutex);
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/* These macros may change in future, to provide better st_ino semantics. */
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#define OFFSET(x) ((x)->i_ino)
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static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
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{
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if (!cino->offset)
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return offset + 1;
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if (!cino->size)
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return offset + 1;
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/*
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* The file mode test fixes buggy mkcramfs implementations where
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* cramfs_inode->offset is set to a non zero value for entries
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* which did not contain data, like devices node and fifos.
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*/
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switch (cino->mode & S_IFMT) {
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case S_IFREG:
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case S_IFDIR:
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case S_IFLNK:
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return cino->offset << 2;
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default:
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break;
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}
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return offset + 1;
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}
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static struct inode *get_cramfs_inode(struct super_block *sb,
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const struct cramfs_inode *cramfs_inode, unsigned int offset)
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{
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struct inode *inode;
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static struct timespec zerotime;
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inode = iget_locked(sb, cramino(cramfs_inode, offset));
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if (!inode)
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return ERR_PTR(-ENOMEM);
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if (!(inode->i_state & I_NEW))
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return inode;
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switch (cramfs_inode->mode & S_IFMT) {
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case S_IFREG:
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inode->i_fop = &generic_ro_fops;
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inode->i_data.a_ops = &cramfs_aops;
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break;
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case S_IFDIR:
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inode->i_op = &cramfs_dir_inode_operations;
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inode->i_fop = &cramfs_directory_operations;
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break;
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case S_IFLNK:
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inode->i_op = &page_symlink_inode_operations;
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inode_nohighmem(inode);
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inode->i_data.a_ops = &cramfs_aops;
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break;
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default:
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init_special_inode(inode, cramfs_inode->mode,
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old_decode_dev(cramfs_inode->size));
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}
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inode->i_mode = cramfs_inode->mode;
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i_uid_write(inode, cramfs_inode->uid);
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i_gid_write(inode, cramfs_inode->gid);
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/* if the lower 2 bits are zero, the inode contains data */
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if (!(inode->i_ino & 3)) {
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inode->i_size = cramfs_inode->size;
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inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
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}
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/* Struct copy intentional */
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inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
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/* inode->i_nlink is left 1 - arguably wrong for directories,
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but it's the best we can do without reading the directory
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contents. 1 yields the right result in GNU find, even
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without -noleaf option. */
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unlock_new_inode(inode);
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return inode;
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}
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/*
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* We have our own block cache: don't fill up the buffer cache
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* with the rom-image, because the way the filesystem is set
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* up the accesses should be fairly regular and cached in the
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* page cache and dentry tree anyway..
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*
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* This also acts as a way to guarantee contiguous areas of up to
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* BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
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* worry about end-of-buffer issues even when decompressing a full
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* page cache.
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*/
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#define READ_BUFFERS (2)
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/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
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#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
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/*
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* BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
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* data that takes up more space than the original and with unlucky
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* alignment.
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*/
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#define BLKS_PER_BUF_SHIFT (2)
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#define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
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#define BUFFER_SIZE (BLKS_PER_BUF*PAGE_SIZE)
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static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
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static unsigned buffer_blocknr[READ_BUFFERS];
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static struct super_block *buffer_dev[READ_BUFFERS];
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static int next_buffer;
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/*
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* Returns a pointer to a buffer containing at least LEN bytes of
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* filesystem starting at byte offset OFFSET into the filesystem.
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*/
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static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
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{
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struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
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struct page *pages[BLKS_PER_BUF];
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unsigned i, blocknr, buffer;
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unsigned long devsize;
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char *data;
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if (!len)
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return NULL;
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blocknr = offset >> PAGE_SHIFT;
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offset &= PAGE_SIZE - 1;
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/* Check if an existing buffer already has the data.. */
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for (i = 0; i < READ_BUFFERS; i++) {
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unsigned int blk_offset;
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if (buffer_dev[i] != sb)
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continue;
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if (blocknr < buffer_blocknr[i])
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continue;
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blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
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blk_offset += offset;
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if (blk_offset + len > BUFFER_SIZE)
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continue;
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return read_buffers[i] + blk_offset;
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}
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devsize = mapping->host->i_size >> PAGE_SHIFT;
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/* Ok, read in BLKS_PER_BUF pages completely first. */
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for (i = 0; i < BLKS_PER_BUF; i++) {
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struct page *page = NULL;
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if (blocknr + i < devsize) {
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page = read_mapping_page(mapping, blocknr + i, NULL);
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/* synchronous error? */
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if (IS_ERR(page))
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page = NULL;
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}
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pages[i] = page;
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}
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for (i = 0; i < BLKS_PER_BUF; i++) {
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struct page *page = pages[i];
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if (page) {
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wait_on_page_locked(page);
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if (!PageUptodate(page)) {
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/* asynchronous error */
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put_page(page);
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pages[i] = NULL;
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}
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}
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}
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buffer = next_buffer;
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next_buffer = NEXT_BUFFER(buffer);
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buffer_blocknr[buffer] = blocknr;
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buffer_dev[buffer] = sb;
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data = read_buffers[buffer];
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for (i = 0; i < BLKS_PER_BUF; i++) {
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struct page *page = pages[i];
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if (page) {
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memcpy(data, kmap(page), PAGE_SIZE);
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kunmap(page);
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put_page(page);
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} else
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memset(data, 0, PAGE_SIZE);
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data += PAGE_SIZE;
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}
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return read_buffers[buffer] + offset;
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}
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static void cramfs_kill_sb(struct super_block *sb)
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{
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struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
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kill_block_super(sb);
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kfree(sbi);
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}
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static int cramfs_remount(struct super_block *sb, int *flags, char *data)
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{
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sync_filesystem(sb);
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*flags |= MS_RDONLY;
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return 0;
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}
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static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
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{
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int i;
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struct cramfs_super super;
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unsigned long root_offset;
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struct cramfs_sb_info *sbi;
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struct inode *root;
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sb->s_flags |= MS_RDONLY;
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sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
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if (!sbi)
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return -ENOMEM;
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sb->s_fs_info = sbi;
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/* Invalidate the read buffers on mount: think disk change.. */
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mutex_lock(&read_mutex);
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for (i = 0; i < READ_BUFFERS; i++)
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buffer_blocknr[i] = -1;
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/* Read the first block and get the superblock from it */
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memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
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mutex_unlock(&read_mutex);
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/* Do sanity checks on the superblock */
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if (super.magic != CRAMFS_MAGIC) {
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/* check for wrong endianness */
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if (super.magic == CRAMFS_MAGIC_WEND) {
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if (!silent)
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pr_err("wrong endianness\n");
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return -EINVAL;
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}
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/* check at 512 byte offset */
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mutex_lock(&read_mutex);
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memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
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mutex_unlock(&read_mutex);
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if (super.magic != CRAMFS_MAGIC) {
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if (super.magic == CRAMFS_MAGIC_WEND && !silent)
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pr_err("wrong endianness\n");
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else if (!silent)
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pr_err("wrong magic\n");
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return -EINVAL;
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}
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}
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/* get feature flags first */
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if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
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pr_err("unsupported filesystem features\n");
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return -EINVAL;
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}
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/* Check that the root inode is in a sane state */
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if (!S_ISDIR(super.root.mode)) {
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pr_err("root is not a directory\n");
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return -EINVAL;
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}
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/* correct strange, hard-coded permissions of mkcramfs */
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super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
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root_offset = super.root.offset << 2;
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if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
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sbi->size = super.size;
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sbi->blocks = super.fsid.blocks;
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sbi->files = super.fsid.files;
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} else {
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sbi->size = 1<<28;
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sbi->blocks = 0;
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sbi->files = 0;
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}
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sbi->magic = super.magic;
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sbi->flags = super.flags;
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if (root_offset == 0)
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pr_info("empty filesystem");
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else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
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((root_offset != sizeof(struct cramfs_super)) &&
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(root_offset != 512 + sizeof(struct cramfs_super))))
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{
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pr_err("bad root offset %lu\n", root_offset);
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return -EINVAL;
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}
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/* Set it all up.. */
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sb->s_op = &cramfs_ops;
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root = get_cramfs_inode(sb, &super.root, 0);
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if (IS_ERR(root))
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return PTR_ERR(root);
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sb->s_root = d_make_root(root);
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if (!sb->s_root)
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return -ENOMEM;
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return 0;
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}
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static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
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{
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struct super_block *sb = dentry->d_sb;
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u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
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buf->f_type = CRAMFS_MAGIC;
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buf->f_bsize = PAGE_SIZE;
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buf->f_blocks = CRAMFS_SB(sb)->blocks;
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buf->f_bfree = 0;
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buf->f_bavail = 0;
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buf->f_files = CRAMFS_SB(sb)->files;
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buf->f_ffree = 0;
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buf->f_fsid.val[0] = (u32)id;
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buf->f_fsid.val[1] = (u32)(id >> 32);
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buf->f_namelen = CRAMFS_MAXPATHLEN;
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return 0;
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}
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/*
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* Read a cramfs directory entry.
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*/
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static int cramfs_readdir(struct file *file, struct dir_context *ctx)
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{
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struct inode *inode = file_inode(file);
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struct super_block *sb = inode->i_sb;
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char *buf;
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unsigned int offset;
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/* Offset within the thing. */
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if (ctx->pos >= inode->i_size)
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return 0;
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offset = ctx->pos;
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/* Directory entries are always 4-byte aligned */
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if (offset & 3)
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return -EINVAL;
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buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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while (offset < inode->i_size) {
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struct cramfs_inode *de;
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unsigned long nextoffset;
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char *name;
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ino_t ino;
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umode_t mode;
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int namelen;
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mutex_lock(&read_mutex);
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de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
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name = (char *)(de+1);
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/*
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* Namelengths on disk are shifted by two
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* and the name padded out to 4-byte boundaries
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* with zeroes.
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*/
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namelen = de->namelen << 2;
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memcpy(buf, name, namelen);
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ino = cramino(de, OFFSET(inode) + offset);
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mode = de->mode;
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mutex_unlock(&read_mutex);
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nextoffset = offset + sizeof(*de) + namelen;
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for (;;) {
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if (!namelen) {
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kfree(buf);
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return -EIO;
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}
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if (buf[namelen-1])
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break;
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namelen--;
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}
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if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
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break;
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ctx->pos = offset = nextoffset;
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}
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kfree(buf);
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return 0;
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}
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/*
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* Lookup and fill in the inode data..
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*/
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static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
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{
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unsigned int offset = 0;
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struct inode *inode = NULL;
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int sorted;
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mutex_lock(&read_mutex);
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sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
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while (offset < dir->i_size) {
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struct cramfs_inode *de;
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char *name;
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int namelen, retval;
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int dir_off = OFFSET(dir) + offset;
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de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
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name = (char *)(de+1);
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/* Try to take advantage of sorted directories */
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if (sorted && (dentry->d_name.name[0] < name[0]))
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break;
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namelen = de->namelen << 2;
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offset += sizeof(*de) + namelen;
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/* Quick check that the name is roughly the right length */
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if (((dentry->d_name.len + 3) & ~3) != namelen)
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continue;
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for (;;) {
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if (!namelen) {
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inode = ERR_PTR(-EIO);
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goto out;
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}
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if (name[namelen-1])
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break;
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namelen--;
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}
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if (namelen != dentry->d_name.len)
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continue;
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retval = memcmp(dentry->d_name.name, name, namelen);
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if (retval > 0)
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continue;
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if (!retval) {
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inode = get_cramfs_inode(dir->i_sb, de, dir_off);
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break;
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}
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/* else (retval < 0) */
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if (sorted)
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break;
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}
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out:
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mutex_unlock(&read_mutex);
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if (IS_ERR(inode))
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return ERR_CAST(inode);
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d_add(dentry, inode);
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return NULL;
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}
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static int cramfs_readpage(struct file *file, struct page *page)
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{
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struct inode *inode = page->mapping->host;
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u32 maxblock;
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int bytes_filled;
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void *pgdata;
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maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
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bytes_filled = 0;
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pgdata = kmap(page);
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if (page->index < maxblock) {
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struct super_block *sb = inode->i_sb;
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u32 blkptr_offset = OFFSET(inode) + page->index*4;
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u32 start_offset, compr_len;
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start_offset = OFFSET(inode) + maxblock*4;
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mutex_lock(&read_mutex);
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if (page->index)
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start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
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4);
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compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
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start_offset);
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mutex_unlock(&read_mutex);
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if (compr_len == 0)
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; /* hole */
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else if (unlikely(compr_len > (PAGE_SIZE << 1))) {
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pr_err("bad compressed blocksize %u\n",
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compr_len);
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goto err;
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} else {
|
|
mutex_lock(&read_mutex);
|
|
bytes_filled = cramfs_uncompress_block(pgdata,
|
|
PAGE_SIZE,
|
|
cramfs_read(sb, start_offset, compr_len),
|
|
compr_len);
|
|
mutex_unlock(&read_mutex);
|
|
if (unlikely(bytes_filled < 0))
|
|
goto err;
|
|
}
|
|
}
|
|
|
|
memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
|
|
flush_dcache_page(page);
|
|
kunmap(page);
|
|
SetPageUptodate(page);
|
|
unlock_page(page);
|
|
return 0;
|
|
|
|
err:
|
|
kunmap(page);
|
|
ClearPageUptodate(page);
|
|
SetPageError(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,
|
|
.iterate_shared = cramfs_readdir,
|
|
};
|
|
|
|
static const struct inode_operations cramfs_dir_inode_operations = {
|
|
.lookup = cramfs_lookup,
|
|
};
|
|
|
|
static const struct super_operations cramfs_ops = {
|
|
.remount_fs = cramfs_remount,
|
|
.statfs = cramfs_statfs,
|
|
};
|
|
|
|
static struct dentry *cramfs_mount(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data)
|
|
{
|
|
return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
|
|
}
|
|
|
|
static struct file_system_type cramfs_fs_type = {
|
|
.owner = THIS_MODULE,
|
|
.name = "cramfs",
|
|
.mount = cramfs_mount,
|
|
.kill_sb = cramfs_kill_sb,
|
|
.fs_flags = FS_REQUIRES_DEV,
|
|
};
|
|
MODULE_ALIAS_FS("cramfs");
|
|
|
|
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");
|