linux/fs/romfs/super.c at master · fabgithub/linux · GitHub

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/* Block- or MTD-based romfs

* Written by David Howells (dhowells@redhat.com)

* Derived from: ROMFS file system, Linux implementation

* Using parts of the minix filesystem

* and parts of the affs filesystem additionally

* Changes

* Changed for 2.1.19 modules

* Jan 1997 Initial release

* Jun 1997 2.1.43+ changes

* Proper page locking in readpage

* Changed to work with 2.1.45+ fs

* Jul 1997 Fixed follow_link

* 2.1.47

* lookup shouldn't return -ENOENT

* from Horst von Brand:

* fail on wrong checksum

* double unlock_super was possible

* correct namelen for statfs

* spotted by Bill Hawes:

* readlink shouldn't iput()

* Jun 1998 2.1.106 from Avery Pennarun: glibc scandir()

* exposed a problem in readdir

* 2.1.107 code-freeze spellchecker run

* Aug 1998 2.1.118+ VFS changes

* Sep 1998 2.1.122 another VFS change (follow_link)

* Apr 1999 2.2.7 no more EBADF checking in

* lookup/readdir, use ERR_PTR

* Jun 1999 2.3.6 d_alloc_root use changed

* 2.3.9 clean up usage of ENOENT/negative

* dentries in lookup

* clean up page flags setting

* (error, uptodate, locking) in

* in readpage

* use init_special_inode for

* fifos/sockets (and streamline) in

* read_inode, fix _ops table order

* Aug 1999 2.3.16 __initfunc() => __init change

* Oct 1999 2.3.24 page->owner hack obsoleted

* Nov 1999 2.3.27 2.3.25+ page->offset => index change

* This program is free software; you can redistribute it and/or

* modify it under the terms of the GNU General Public Licence

* as published by the Free Software Foundation; either version

* 2 of the Licence, or (at your option) any later version.

#include <linux/module.h>

#include <linux/string.h>

#include <linux/fs.h>

#include <linux/time.h>

#include <linux/slab.h>

#include <linux/init.h>

#include <linux/blkdev.h>

#include <linux/parser.h>

#include <linux/mount.h>

#include <linux/namei.h>

#include <linux/statfs.h>

#include <linux/mtd/super.h>

#include <linux/ctype.h>

#include <linux/highmem.h>

#include <linux/pagemap.h>

#include <linux/uaccess.h>

#include "internal.h"

static struct kmem_cache *romfs_inode_cachep;

static const umode_t romfs_modemap[8] = {

0, /* hard link */

S_IFDIR | 0644, /* directory */

S_IFREG | 0644, /* regular file */

S_IFLNK | 0777, /* symlink */

S_IFBLK | 0600, /* blockdev */

S_IFCHR | 0600, /* chardev */

S_IFSOCK | 0644, /* socket */

S_IFIFO | 0644 /* FIFO */

};

static const unsigned char romfs_dtype_table[] = {

DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO

};

static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);

* read a page worth of data from the image

static int romfs_readpage(struct file *file, struct page *page)

{

struct inode *inode = page->mapping->host;

loff_t offset, size;

unsigned long fillsize, pos;

void *buf;

int ret;

buf = kmap(page);

if (!buf)

return -ENOMEM;

/* 32 bit warning -- but not for us :) */

offset = page_offset(page);

size = i_size_read(inode);

fillsize = 0;

ret = 0;

if (offset < size) {

size -= offset;

fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;

pos = ROMFS_I(inode)->i_dataoffset + offset;

ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);

if (ret < 0) {

SetPageError(page);

fillsize = 0;

ret = -EIO;

}

if (fillsize < PAGE_SIZE)

memset(buf + fillsize, 0, PAGE_SIZE - fillsize);

if (ret == 0)

SetPageUptodate(page);

flush_dcache_page(page);

kunmap(page);

unlock_page(page);

return ret;

}

static const struct address_space_operations romfs_aops = {

.readpage = romfs_readpage

};

* read the entries from a directory

static int romfs_readdir(struct file *file, struct dir_context *ctx)

{

struct inode *i = file_inode(file);

struct romfs_inode ri;

unsigned long offset, maxoff;

int j, ino, nextfh;

char fsname[ROMFS_MAXFN]; /* XXX dynamic? */

int ret;

maxoff = romfs_maxsize(i->i_sb);

offset = ctx->pos;

if (!offset) {

offset = i->i_ino & ROMFH_MASK;

ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);

if (ret < 0)

goto out;

offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

}

/* Not really failsafe, but we are read-only... */

for (;;) {

if (!offset || offset >= maxoff) {

offset = maxoff;

ctx->pos = offset;

goto out;

}

ctx->pos = offset;

/* Fetch inode info */

ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);

if (ret < 0)

goto out;

j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,

sizeof(fsname) - 1);

if (j < 0)

goto out;

ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);

if (ret < 0)

goto out;

fsname[j] = '\0';

ino = offset;

nextfh = be32_to_cpu(ri.next);

if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)

ino = be32_to_cpu(ri.spec);

if (!dir_emit(ctx, fsname, j, ino,

romfs_dtype_table[nextfh & ROMFH_TYPE]))

goto out;

offset = nextfh & ROMFH_MASK;

}

out:

return 0;

}

* look up an entry in a directory

static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,

unsigned int flags)

{

unsigned long offset, maxoff;

struct inode *inode;

struct romfs_inode ri;

const char *name; /* got from dentry */

int len, ret;

offset = dir->i_ino & ROMFH_MASK;

ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);

if (ret < 0)

goto error;

/* search all the file entries in the list starting from the one

* pointed to by the directory's special data */

maxoff = romfs_maxsize(dir->i_sb);

offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

name = dentry->d_name.name;

len = dentry->d_name.len;

for (;;) {

if (!offset || offset >= maxoff)

goto out0;

ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));

if (ret < 0)

goto error;

/* try to match the first 16 bytes of name */

ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,

len);

if (ret < 0)

goto error;

if (ret == 1)

break;

/* next entry */

offset = be32_to_cpu(ri.next) & ROMFH_MASK;

}

/* Hard link handling */

if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)

offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

inode = romfs_iget(dir->i_sb, offset);

if (IS_ERR(inode)) {

ret = PTR_ERR(inode);

goto error;

}

goto outi;

* it's a bit funky, _lookup needs to return an error code

* (negative) or a NULL, both as a dentry. ENOENT should not

* be returned, instead we need to create a negative dentry by

* d_add(dentry, NULL); and return 0 as no error.

* (Although as I see, it only matters on writable file

* systems).

out0:

inode = NULL;

outi:

d_add(dentry, inode);

ret = 0;

error:

return ERR_PTR(ret);

}

static const struct file_operations romfs_dir_operations = {

.read = generic_read_dir,

.iterate = romfs_readdir,

.llseek = default_llseek,

};

static const struct inode_operations romfs_dir_inode_operations = {

.lookup = romfs_lookup,

};

* get a romfs inode based on its position in the image (which doubles as the

* inode number)

static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)

{

struct romfs_inode_info *inode;

struct romfs_inode ri;

struct inode *i;

unsigned long nlen;

unsigned nextfh;

int ret;

umode_t mode;

/* we might have to traverse a chain of "hard link" file entries to get

* to the actual file */

for (;;) {

ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));

if (ret < 0)

goto error;

/* XXX: do romfs_checksum here too (with name) */

nextfh = be32_to_cpu(ri.next);

if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)

break;

pos = be32_to_cpu(ri.spec) & ROMFH_MASK;

}

/* determine the length of the filename */

nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);

if (IS_ERR_VALUE(nlen))

goto eio;

/* get an inode for this image position */

i = iget_locked(sb, pos);

if (!i)

return ERR_PTR(-ENOMEM);

if (!(i->i_state & I_NEW))

return i;

/* precalculate the data offset */

inode = ROMFS_I(i);

inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;

inode->i_dataoffset = pos + inode->i_metasize;

set_nlink(i, 1); /* Hard to decide.. */

i->i_size = be32_to_cpu(ri.size);

i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;

i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;

/* set up mode and ops */

mode = romfs_modemap[nextfh & ROMFH_TYPE];

switch (nextfh & ROMFH_TYPE) {

case ROMFH_DIR:

i->i_size = ROMFS_I(i)->i_metasize;

i->i_op = &romfs_dir_inode_operations;

i->i_fop = &romfs_dir_operations;

if (nextfh & ROMFH_EXEC)

mode |= S_IXUGO;

break;

case ROMFH_REG:

i->i_fop = &romfs_ro_fops;

i->i_data.a_ops = &romfs_aops;

if (i->i_sb->s_mtd)

i->i_data.backing_dev_info =

i->i_sb->s_mtd->backing_dev_info;

if (nextfh & ROMFH_EXEC)

mode |= S_IXUGO;

break;

case ROMFH_SYM:

i->i_op = &page_symlink_inode_operations;

i->i_data.a_ops = &romfs_aops;

mode |= S_IRWXUGO;

break;

default:

/* depending on MBZ for sock/fifos */

nextfh = be32_to_cpu(ri.spec);

init_special_inode(i, mode, MKDEV(nextfh >> 16,

nextfh & 0xffff));

break;

}

i->i_mode = mode;

unlock_new_inode(i);

return i;

eio:

ret = -EIO;

error:

printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);

return ERR_PTR(ret);

}

* allocate a new inode

static struct inode *romfs_alloc_inode(struct super_block *sb)

{

struct romfs_inode_info *inode;

inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);

return inode ? &inode->vfs_inode : NULL;

}

* return a spent inode to the slab cache

static void romfs_i_callback(struct rcu_head *head)

{

struct inode *inode = container_of(head, struct inode, i_rcu);

kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));

}

static void romfs_destroy_inode(struct inode *inode)

{

call_rcu(&inode->i_rcu, romfs_i_callback);

}

* get filesystem statistics

static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)

{

struct super_block *sb = dentry->d_sb;

u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

buf->f_type = ROMFS_MAGIC;

buf->f_namelen = ROMFS_MAXFN;

buf->f_bsize = ROMBSIZE;

buf->f_bfree = buf->f_bavail = buf->f_ffree;

buf->f_blocks =

(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;

buf->f_fsid.val[0] = (u32)id;

buf->f_fsid.val[1] = (u32)(id >> 32);

return 0;

}

* remounting must involve read-only

static int romfs_remount(struct super_block *sb, int *flags, char *data)

{

*flags |= MS_RDONLY;

return 0;

}

static const struct super_operations romfs_super_ops = {

.alloc_inode = romfs_alloc_inode,

.destroy_inode = romfs_destroy_inode,

.statfs = romfs_statfs,

.remount_fs = romfs_remount,

};

* checksum check on part of a romfs filesystem

static __u32 romfs_checksum(const void *data, int size)

{

const __be32 *ptr = data;

__u32 sum;

sum = 0;

size >>= 2;

while (size > 0) {

sum += be32_to_cpu(*ptr++);

size--;

}

return sum;

}

* fill in the superblock

static int romfs_fill_super(struct super_block *sb, void *data, int silent)

{

struct romfs_super_block *rsb;

struct inode *root;

unsigned long pos, img_size;

const char *storage;

size_t len;

int ret;

#ifdef CONFIG_BLOCK

if (!sb->s_mtd) {

sb_set_blocksize(sb, ROMBSIZE);

} else {

sb->s_blocksize = ROMBSIZE;

sb->s_blocksize_bits = blksize_bits(ROMBSIZE);

}

#endif

sb->s_maxbytes = 0xFFFFFFFF;

sb->s_magic = ROMFS_MAGIC;

sb->s_flags |= MS_RDONLY | MS_NOATIME;

sb->s_op = &romfs_super_ops;

/* read the image superblock and check it */

rsb = kmalloc(512, GFP_KERNEL);

if (!rsb)

return -ENOMEM;

sb->s_fs_info = (void *) 512;

ret = romfs_dev_read(sb, 0, rsb, 512);

if (ret < 0)

goto error_rsb;

img_size = be32_to_cpu(rsb->size);

if (sb->s_mtd && img_size > sb->s_mtd->size)

goto error_rsb_inval;

sb->s_fs_info = (void *) img_size;

if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||

img_size < ROMFH_SIZE) {

if (!silent)

printk(KERN_WARNING "VFS:"

" Can't find a romfs filesystem on dev %s.\n",

sb->s_id);

goto error_rsb_inval;

}

if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {

printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",

sb->s_id);

goto error_rsb_inval;

}

storage = sb->s_mtd ? "MTD" : "the block layer";

len = strnlen(rsb->name, ROMFS_MAXFN);

if (!silent)

printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",

(unsigned) len, (unsigned) len, rsb->name, storage);

kfree(rsb);

rsb = NULL;

/* find the root directory */

pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;

root = romfs_iget(sb, pos);

if (IS_ERR(root))

goto error;

sb->s_root = d_make_root(root);

if (!sb->s_root)

goto error;

return 0;

error:

return -EINVAL;

error_rsb_inval:

ret = -EINVAL;

error_rsb:

kfree(rsb);

return ret;

}

* get a superblock for mounting

static struct dentry *romfs_mount(struct file_system_type *fs_type,

int flags, const char *dev_name,

void *data)

{

struct dentry *ret = ERR_PTR(-EINVAL);

#ifdef CONFIG_ROMFS_ON_MTD

ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);

#endif

#ifdef CONFIG_ROMFS_ON_BLOCK

if (ret == ERR_PTR(-EINVAL))

ret = mount_bdev(fs_type, flags, dev_name, data,

romfs_fill_super);

#endif

return ret;

}

* destroy a romfs superblock in the appropriate manner

static void romfs_kill_sb(struct super_block *sb)

{

#ifdef CONFIG_ROMFS_ON_MTD

if (sb->s_mtd) {

kill_mtd_super(sb);

return;

}

#endif

#ifdef CONFIG_ROMFS_ON_BLOCK

if (sb->s_bdev) {

kill_block_super(sb);

return;

}

#endif

}

static struct file_system_type romfs_fs_type = {

.owner = THIS_MODULE,

.name = "romfs",

.mount = romfs_mount,

.kill_sb = romfs_kill_sb,

.fs_flags = FS_REQUIRES_DEV,

};

MODULE_ALIAS_FS("romfs");

* inode storage initialiser

static void romfs_i_init_once(void *_inode)

{

struct romfs_inode_info *inode = _inode;

inode_init_once(&inode->vfs_inode);

}

* romfs module initialisation

static int __init init_romfs_fs(void)

{

int ret;

romfs_inode_cachep =

kmem_cache_create("romfs_i",

sizeof(struct romfs_inode_info), 0,

SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,

romfs_i_init_once);

if (!romfs_inode_cachep) {

printk(KERN_ERR

"ROMFS error: Failed to initialise inode cache\n");

return -ENOMEM;

}

ret = register_filesystem(&romfs_fs_type);

if (ret) {

printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");

goto error_register;

}

return 0;

error_register:

kmem_cache_destroy(romfs_inode_cachep);

return ret;

}

* romfs module removal

static void __exit exit_romfs_fs(void)

{

unregister_filesystem(&romfs_fs_type);

* Make sure all delayed rcu free inodes are flushed before we

* destroy cache.

rcu_barrier();

kmem_cache_destroy(romfs_inode_cachep);

}

module_init(init_romfs_fs);

module_exit(exit_romfs_fs);

MODULE_DESCRIPTION("Direct-MTD Capable RomFS");

MODULE_AUTHOR("Red Hat, Inc.");

MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */

linux/fs/romfs/super.c at master · fabgithub/linux · GitHub

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