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![Stefani Seibold](/assets/img/avatar_default.png)
Generate a unique inode numbers for any entries in the cram file system. For files which did not contain data's (device nodes, fifos and sockets) the offset of the directory entry inside the cramfs plus 1 will be used as inode number. The + 1 for the inode will it make possible to distinguish between a file which contains no data and files which has data, the later one has a inode value where the lower two bits are always 0. It also reimplements the behavior to set the size and the number of block to 0 for special file, which is the right value for empty files, devices, fifos and sockets As a little benefit it will be also more compatible which older mkcramfs, because it will never use the cramfs_inode->offset for creating a inode number for special files. [akpm@linux-foundation.org: trivial comment fix] [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Stefani Seibold <stefani@seibold.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
599 lines
14 KiB
C
599 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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#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/cramfs_fs.h>
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#include <linux/slab.h>
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#include <linux/cramfs_fs_sb.h>
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#include <linux/buffer_head.h>
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#include <linux/vfs.h>
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#include <linux/mutex.h>
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#include <asm/uaccess.h>
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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(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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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->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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inode->i_uid = cramfs_inode->uid;
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inode->i_gid = 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_CACHE_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_CACHE_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_CACHE_SHIFT;
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offset &= PAGE_CACHE_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_CACHE_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_CACHE_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_async(mapping, blocknr + i,
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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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page_cache_release(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_CACHE_SIZE);
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kunmap(page);
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page_cache_release(page);
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} else
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memset(data, 0, PAGE_CACHE_SIZE);
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data += PAGE_CACHE_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_put_super(struct super_block *sb)
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{
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kfree(sb->s_fs_info);
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sb->s_fs_info = NULL;
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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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*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 endianess */
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if (super.magic == CRAMFS_MAGIC_WEND) {
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if (!silent)
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printk(KERN_ERR "cramfs: wrong endianess\n");
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goto out;
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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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printk(KERN_ERR "cramfs: wrong endianess\n");
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else if (!silent)
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printk(KERN_ERR "cramfs: wrong magic\n");
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goto out;
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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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printk(KERN_ERR "cramfs: unsupported filesystem features\n");
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goto out;
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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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printk(KERN_ERR "cramfs: root is not a directory\n");
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goto out;
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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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printk(KERN_INFO "cramfs: 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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printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
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goto out;
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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 (!root)
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goto out;
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sb->s_root = d_alloc_root(root);
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if (!sb->s_root) {
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iput(root);
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goto out;
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}
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return 0;
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out:
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kfree(sbi);
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sb->s_fs_info = NULL;
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return -EINVAL;
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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_CACHE_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 *filp, void *dirent, filldir_t filldir)
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{
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struct inode *inode = filp->f_path.dentry->d_inode;
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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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int copied;
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/* Offset within the thing. */
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offset = filp->f_pos;
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if (offset >= inode->i_size)
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return 0;
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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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copied = 0;
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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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mode_t mode;
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int namelen, error;
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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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error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
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if (error)
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break;
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offset = nextoffset;
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filp->f_pos = offset;
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copied++;
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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, struct nameidata *nd)
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{
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unsigned int offset = 0;
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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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mutex_unlock(&read_mutex);
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return ERR_PTR(-EIO);
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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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struct cramfs_inode entry = *de;
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mutex_unlock(&read_mutex);
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d_add(dentry, get_cramfs_inode(dir->i_sb, &entry, dir_off));
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return NULL;
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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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mutex_unlock(&read_mutex);
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d_add(dentry, NULL);
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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_CACHE_SIZE - 1) >> PAGE_CACHE_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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|
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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);
|
|
|
|
if (compr_len == 0)
|
|
; /* hole */
|
|
else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
|
|
pr_err("cramfs: bad compressed blocksize %u\n",
|
|
compr_len);
|
|
goto err;
|
|
} 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);
|
|
if (unlikely(bytes_filled < 0))
|
|
goto err;
|
|
}
|
|
}
|
|
|
|
memset(pgdata + bytes_filled, 0, PAGE_CACHE_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,
|
|
.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 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 = 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");
|