inode.c

嵌入式系统设计与实验教材二源码linux内核移植与编译

/*
 *  linux/fs/fat/inode.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *  VFAT extensions by Gordon Chaffee, merged with msdos fs by Henrik Storner
 *  Rewritten for the constant inumbers support by Al Viro
 *
 *  Fixes:
 *
 *  	Max Cohan: Fixed invalid FSINFO offset when info_sector is 0
 */

#include <linux/module.h>
#include <linux/msdos_fs.h>
#include <linux/nls.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/bitops.h>
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/locks.h>
#include <linux/fat_cvf.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>
#include <asm/unaligned.h>

extern struct cvf_format default_cvf;

/* #define FAT_PARANOIA 1 */
#define DEBUG_LEVEL 0
#ifdef FAT_DEBUG
#  define PRINTK(x) printk x
#else
#  define PRINTK(x)
#endif
#if (DEBUG_LEVEL >= 1)
#  define PRINTK1(x) printk x
#else
#  define PRINTK1(x)
#endif

/*
 * New FAT inode stuff. We do the following:
 *	a) i_ino is constant and has nothing with on-disk location.
 *	b) FAT manages its own cache of directory entries.
 *	c) *This* cache is indexed by on-disk location.
 *	d) inode has an associated directory entry, all right, but
 *		it may be unhashed.
 *	e) currently entries are stored within struct inode. That should
 *		change.
 *	f) we deal with races in the following way:
 *		1. readdir() and lookup() do FAT-dir-cache lookup.
 *		2. rename() unhashes the F-d-c entry and rehashes it in
 *			a new place.
 *		3. unlink() and rmdir() unhash F-d-c entry.
 *		4. fat_write_inode() checks whether the thing is unhashed.
 *			If it is we silently return. If it isn't we do bread(),
 *			check if the location is still valid and retry if it
 *			isn't. Otherwise we do changes.
 *		5. Spinlock is used to protect hash/unhash/location check/lookup
 *		6. fat_clear_inode() unhashes the F-d-c entry.
 *		7. lookup() and readdir() do igrab() if they find a F-d-c entry
 *			and consider negative result as cache miss.
 */

#define FAT_HASH_BITS	8
#define FAT_HASH_SIZE	(1UL << FAT_HASH_BITS)
#define FAT_HASH_MASK	(FAT_HASH_SIZE-1)
static struct list_head fat_inode_hashtable[FAT_HASH_SIZE];
spinlock_t fat_inode_lock = SPIN_LOCK_UNLOCKED;

void fat_hash_init(void)
{
	int i;
	for(i = 0; i < FAT_HASH_SIZE; i++) {
		INIT_LIST_HEAD(&fat_inode_hashtable[i]);
	}
}

static inline unsigned long fat_hash(struct super_block *sb, int i_pos)
{
	unsigned long tmp = (unsigned long)i_pos | (unsigned long) sb;
	tmp = tmp + (tmp >> FAT_HASH_BITS) + (tmp >> FAT_HASH_BITS * 2);
	return tmp & FAT_HASH_MASK;
}

void fat_attach(struct inode *inode, int i_pos)
{
	spin_lock(&fat_inode_lock);
	MSDOS_I(inode)->i_location = i_pos;
	list_add(&MSDOS_I(inode)->i_fat_hash,
		fat_inode_hashtable + fat_hash(inode->i_sb, i_pos));
	spin_unlock(&fat_inode_lock);
}

void fat_detach(struct inode *inode)
{
	spin_lock(&fat_inode_lock);
	MSDOS_I(inode)->i_location = 0;
	list_del(&MSDOS_I(inode)->i_fat_hash);
	INIT_LIST_HEAD(&MSDOS_I(inode)->i_fat_hash);
	spin_unlock(&fat_inode_lock);
}

struct inode *fat_iget(struct super_block *sb, int i_pos)
{
	struct list_head *p = fat_inode_hashtable + fat_hash(sb, i_pos);
	struct list_head *walk;
	struct msdos_inode_info *i;
	struct inode *inode = NULL;

	spin_lock(&fat_inode_lock);
	list_for_each(walk, p) {
		i = list_entry(walk, struct msdos_inode_info, i_fat_hash);
		if (i->i_fat_inode->i_sb != sb)
			continue;
		if (i->i_location != i_pos)
			continue;
		inode = igrab(i->i_fat_inode);
		if (inode)
			break;
	}
	spin_unlock(&fat_inode_lock);
	return inode;
}

static void fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de);

struct inode *fat_build_inode(struct super_block *sb,
				struct msdos_dir_entry *de, int ino, int *res)
{
	struct inode *inode;
	*res = 0;
	inode = fat_iget(sb, ino);
	if (inode)
		goto out;
	inode = new_inode(sb);
	*res = -ENOMEM;
	if (!inode)
		goto out;
	*res = 0;
	inode->i_ino = iunique(sb, MSDOS_ROOT_INO);
	fat_fill_inode(inode, de);
	fat_attach(inode, ino);
	insert_inode_hash(inode);
out:
	return inode;
}

void fat_delete_inode(struct inode *inode)
{
	if (!is_bad_inode(inode)) {
		lock_kernel();
		inode->i_size = 0;
		fat_truncate(inode);
		unlock_kernel();
	}
	clear_inode(inode);
}

void fat_clear_inode(struct inode *inode)
{
	if (is_bad_inode(inode))
		return;
	lock_kernel();
	spin_lock(&fat_inode_lock);
	fat_cache_inval_inode(inode);
	list_del(&MSDOS_I(inode)->i_fat_hash);
	spin_unlock(&fat_inode_lock);
	unlock_kernel();
}

void fat_put_super(struct super_block *sb)
{
	if (MSDOS_SB(sb)->cvf_format->cvf_version) {
		dec_cvf_format_use_count_by_version(MSDOS_SB(sb)->cvf_format->cvf_version);
		MSDOS_SB(sb)->cvf_format->unmount_cvf(sb);
	}
	if (MSDOS_SB(sb)->fat_bits == 32) {
		fat_clusters_flush(sb);
	}
	fat_cache_inval_dev(sb->s_dev);
	set_blocksize (sb->s_dev,BLOCK_SIZE);
	if (MSDOS_SB(sb)->nls_disk) {
		unload_nls(MSDOS_SB(sb)->nls_disk);
		MSDOS_SB(sb)->nls_disk = NULL;
		MSDOS_SB(sb)->options.codepage = 0;
	}
	if (MSDOS_SB(sb)->nls_io) {
		unload_nls(MSDOS_SB(sb)->nls_io);
		MSDOS_SB(sb)->nls_io = NULL;
	}
	/*
	 * Note: the iocharset option might have been specified
	 * without enabling nls_io, so check for it here.
	 */
	if (MSDOS_SB(sb)->options.iocharset) {
		kfree(MSDOS_SB(sb)->options.iocharset);
		MSDOS_SB(sb)->options.iocharset = NULL;
	}
}


static int parse_options(char *options,int *fat, int *debug,
			 struct fat_mount_options *opts,
			 char *cvf_format, char *cvf_options)
{
	char *this_char,*value,save,*savep;
	char *p;
	int ret = 1, len;

	opts->name_check = 'n';
	opts->conversion = 'b';
	opts->fs_uid = current->uid;
	opts->fs_gid = current->gid;
	opts->fs_umask = current->fs->umask;
	opts->quiet = opts->sys_immutable = opts->dotsOK = opts->showexec = 0;
	opts->codepage = 0;
	opts->nocase = 0;
	opts->shortname = 0;
	opts->utf8 = 0;
	opts->iocharset = NULL;
	*debug = *fat = 0;

	if (!options)
		goto out;
	save = 0;
	savep = NULL;
	for (this_char = strtok(options,","); this_char;
	     this_char = strtok(NULL,",")) {
		if ((value = strchr(this_char,'=')) != NULL) {
			save = *value;
			savep = value;
			*value++ = 0;
		}
		if (!strcmp(this_char,"check") && value) {
			if (value[0] && !value[1] && strchr("rns",*value))
				opts->name_check = *value;
			else if (!strcmp(value,"relaxed"))
				opts->name_check = 'r';
			else if (!strcmp(value,"normal"))
				opts->name_check = 'n';
			else if (!strcmp(value,"strict"))
				opts->name_check = 's';
			else ret = 0;
		}
		else if (!strcmp(this_char,"conv") && value) {
			if (value[0] && !value[1] && strchr("bta",*value))
				opts->conversion = *value;
			else if (!strcmp(value,"binary"))
				opts->conversion = 'b';
			else if (!strcmp(value,"text"))
				opts->conversion = 't';
			else if (!strcmp(value,"auto"))
				opts->conversion = 'a';
			else ret = 0;
		}
		else if (!strcmp(this_char,"dots")) {
			opts->dotsOK = 1;
		}
		else if (!strcmp(this_char,"nocase")) {
			opts->nocase = 1;
		}
		else if (!strcmp(this_char,"nodots")) {
			opts->dotsOK = 0;
		}
		else if (!strcmp(this_char,"showexec")) {
			opts->showexec = 1;
		}
		else if (!strcmp(this_char,"dotsOK") && value) {
			if (!strcmp(value,"yes")) opts->dotsOK = 1;
			else if (!strcmp(value,"no")) opts->dotsOK = 0;
			else ret = 0;
		}
		else if (!strcmp(this_char,"uid")) {
			if (!value || !*value) ret = 0;
			else {
				opts->fs_uid = simple_strtoul(value,&value,0);
				if (*value) ret = 0;
			}
		}
		else if (!strcmp(this_char,"gid")) {
			if (!value || !*value) ret= 0;
			else {
				opts->fs_gid = simple_strtoul(value,&value,0);
				if (*value) ret = 0;
			}
		}
		else if (!strcmp(this_char,"umask")) {
			if (!value || !*value) ret = 0;
			else {
				opts->fs_umask = simple_strtoul(value,&value,8);
				if (*value) ret = 0;
			}
		}
		else if (!strcmp(this_char,"debug")) {
			if (value) ret = 0;
			else *debug = 1;
		}
		else if (!strcmp(this_char,"fat")) {
			if (!value || !*value) ret = 0;
			else {
				*fat = simple_strtoul(value,&value,0);
				if (*value || (*fat != 12 && *fat != 16 &&
					       *fat != 32)) 
					ret = 0;
			}
		}
		else if (!strcmp(this_char,"quiet")) {
			if (value) ret = 0;
			else opts->quiet = 1;
		}
		else if (!strcmp(this_char,"blocksize")) {
			printk("FAT: blocksize option is obsolete, "
			       "not supported now\n");
		}
		else if (!strcmp(this_char,"sys_immutable")) {
			if (value) ret = 0;
			else opts->sys_immutable = 1;
		}
		else if (!strcmp(this_char,"codepage") && value) {
			opts->codepage = simple_strtoul(value,&value,0);
			if (*value) ret = 0;
			else printk ("MSDOS FS: Using codepage %d\n",
					opts->codepage);
		}
		else if (!strcmp(this_char,"iocharset") && value) {
			p = value;
			while (*value && *value != ',')
				value++;
			len = value - p;
			if (len) {
				char *buffer;

				if (opts->iocharset != NULL) {
					kfree(opts->iocharset);
					opts->iocharset = NULL;
				}
				buffer = kmalloc(len + 1, GFP_KERNEL);
				if (buffer != NULL) {
					opts->iocharset = buffer;
					memcpy(buffer, p, len);
					buffer[len] = 0;
					printk("MSDOS FS: IO charset %s\n", buffer);
				} else
					ret = 0;
			}
		}
		else if (!strcmp(this_char,"cvf_format")) {
			if (!value)
				return 0;
			strncpy(cvf_format,value,20);
		}
		else if (!strcmp(this_char,"cvf_options")) {
			if (!value)
				return 0;
			strncpy(cvf_options,value,100);
		}

		if (this_char != options) *(this_char-1) = ',';
		if (value) *savep = save;
		if (ret == 0)
			break;
	}
out:
	return ret;
}

static void fat_read_root(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int nr;

	INIT_LIST_HEAD(&MSDOS_I(inode)->i_fat_hash);
	MSDOS_I(inode)->i_location = 0;
	MSDOS_I(inode)->i_fat_inode = inode;
	inode->i_uid = sbi->options.fs_uid;
	inode->i_gid = sbi->options.fs_gid;
	inode->i_version = ++event;
	inode->i_generation = 0;
	inode->i_mode = (S_IRWXUGO & ~sbi->options.fs_umask) | S_IFDIR;
	inode->i_op = sbi->dir_ops;
	inode->i_fop = &fat_dir_operations;
	if (sbi->fat_bits == 32) {
		MSDOS_I(inode)->i_start = sbi->root_cluster;
		if ((nr = MSDOS_I(inode)->i_start) != 0) {
			while (nr != -1) {
				inode->i_size += 1 << sbi->cluster_bits;
				if (!(nr = fat_access(sb, nr, -1))) {
					printk("Directory %ld: bad FAT\n",
					       inode->i_ino);
					break;
				}
			}
		}
	} else {
		MSDOS_I(inode)->i_start = 0;
		inode->i_size = sbi->dir_entries * sizeof(struct msdos_dir_entry);
	}
	inode->i_blksize = 1 << sbi->cluster_bits;
	inode->i_blocks = ((inode->i_size + inode->i_blksize - 1)
			   & ~(inode->i_blksize - 1)) >> 9;
	MSDOS_I(inode)->i_logstart = 0;
	MSDOS_I(inode)->mmu_private = inode->i_size;

	MSDOS_I(inode)->i_attrs = 0;
	inode->i_mtime = inode->i_atime = inode->i_ctime = 0;
	MSDOS_I(inode)->i_ctime_ms = 0;
	inode->i_nlink = fat_subdirs(inode)+2;
}

/*
 * a FAT file handle with fhtype 3 is
 *  0/  i_ino - for fast, reliable lookup if still in the cache
 *  1/  i_generation - to see if i_ino is still valid
 *          bit 0 == 0 iff directory
 *  2/  i_location - if ino has changed, but still in cache
 *  3/  i_logstart - to semi-verify inode found at i_location
 *  4/  parent->i_logstart - maybe used to hunt for the file on disc
 *
 */
struct dentry *fat_fh_to_dentry(struct super_block *sb, __u32 *fh,
				int len, int fhtype, int parent)
{
	struct inode *inode = NULL;
	struct list_head *lp;
	struct dentry *result;

	if (fhtype != 3)
		return NULL;
	if (len < 5)
		return NULL;
	if (parent)
		return NULL; /* We cannot find the parent,
				It better just *be* there */

	inode = iget(sb, fh[0]);
	if (!inode || is_bad_inode(inode) ||
	    inode->i_generation != fh[1]) {
		if (inode) iput(inode);
		inode = NULL;
	}
	if (!inode) {
		/* try 2 - see if i_location is in F-d-c
		 * require i_logstart to be the same
		 * Will fail if you truncate and then re-write
		 */

		inode = fat_iget(sb, fh[2]);
		if (inode && MSDOS_I(inode)->i_logstart != fh[3]) {
			iput(inode);
			inode = NULL;
		}
	}
	if (!inode) {
		/* For now, do nothing
		 * What we could do is:
		 * follow the file starting at fh[4], and record
		 * the ".." entry, and the name of the fh[2] entry.
		 * The follow the ".." file finding the next step up.
		 * This way we build a path to the root of
		 * the tree. If this works, we lookup the path and so
		 * get this inode into the cache.
		 * Finally try the fat_iget lookup again
		 * If that fails, then weare totally out of luck
		 * But all that is for another day
		 */
	}
	if (!inode)
		return ERR_PTR(-ESTALE);

	
	/* now to find a dentry.
	 * If possible, get a well-connected one
	 *
	 * Given the way that we found the inode, it *MUST* be
	 * well-connected, but it is easiest to just copy the
	 * code.
	 */
	spin_lock(&dcache_lock);
	for (lp = inode->i_dentry.next; lp != &inode->i_dentry ; lp=lp->next) {
		result = list_entry(lp,struct dentry, d_alias);
		if (! (result->d_flags & DCACHE_NFSD_DISCONNECTED)) {
			dget_locked(result);
			result->d_vfs_flags |= DCACHE_REFERENCED;
			spin_unlock(&dcache_lock);
			iput(inode);
			return result;
		}
	}
	spin_unlock(&dcache_lock);
	result = d_alloc_root(inode);
	if (result == NULL) {
		iput(inode);
		return ERR_PTR(-ENOMEM);
	}
	result->d_flags |= DCACHE_NFSD_DISCONNECTED;
	return result;

		
}

int fat_dentry_to_fh(struct dentry *de, __u32 *fh, int *lenp, int needparent)
{
	int len = *lenp;
	struct inode *inode =  de->d_inode;
	
	if (len < 5)
		return 255; /* no room */
	*lenp = 5;
	fh[0] = inode->i_ino;
	fh[1] = inode->i_generation;
	fh[2] = MSDOS_I(inode)->i_location;
	fh[3] = MSDOS_I(inode)->i_logstart;
	fh[4] = MSDOS_I(de->d_parent->d_inode)->i_logstart;
	return 3;
}

static struct super_operations fat_sops = { 
	write_inode:	fat_write_inode,
	delete_inode:	fat_delete_inode,
	put_super:	fat_put_super,
	statfs:		fat_statfs,
	clear_inode:	fat_clear_inode,