namei.c

基于linux1.0内核的linux源码

/*
 *  linux/fs/msdos/namei.c
 *
 *  Written 1992,1993 by Werner Almesberger
 */

#include <asm/segment.h>

#include <linux/sched.h>
#include <linux/msdos_fs.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>

/* MS-DOS "device special files" */

static char *reserved_names[] = {
    "CON     ","PRN     ","NUL     ","AUX     ",
    "LPT1    ","LPT2    ","LPT3    ","LPT4    ",
    "COM1    ","COM2    ","COM3    ","COM4    ",
    NULL };


/* Characters that are undesirable in an MS-DOS file name */
  
static char bad_chars[] = "*?<>|\"";
static char bad_if_strict[] = "+=,; ";


/* Formats an MS-DOS file name. Rejects invalid names. */

static int msdos_format_name(char conv,const char *name,int len,char *res,
  int dot_dirs)
{
	char *walk,**reserved;
	unsigned char c;
	int space;

	if (IS_FREE(name)) return -EINVAL;
	if (name[0] == '.' && (len == 1 || (len == 2 && name[1] == '.'))) {
		if (!dot_dirs) return -EEXIST;
		memset(res+1,' ',10);
		while (len--) *res++ = '.';
		return 0;
	}
	space = 1; /* disallow names starting with a dot */
	c = 0;
	for (walk = res; len && walk-res < 8; walk++) {
	    	c = *name++;
		len--;
		if (conv != 'r' && strchr(bad_chars,c)) return -EINVAL;
		if (conv == 's' && strchr(bad_if_strict,c)) return -EINVAL;
  		if (c >= 'A' && c <= 'Z' && conv == 's') return -EINVAL;
		if (c < ' ' || c == ':' || c == '\\') return -EINVAL;
		if (c == '.') break;
		space = c == ' ';
		*walk = c >= 'a' && c <= 'z' ? c-32 : c;
	}
	if (space) return -EINVAL;
	if (conv == 's' && len && c != '.') {
		c = *name++;
		len--;
		if (c != '.') return -EINVAL;
	}
	while (c != '.' && len--) c = *name++;
	if (c == '.') {
		while (walk-res < 8) *walk++ = ' ';
		while (len > 0 && walk-res < MSDOS_NAME) {
			c = *name++;
			len--;
			if (conv != 'r' && strchr(bad_chars,c)) return -EINVAL;
			if (conv == 's' && strchr(bad_if_strict,c))
				return -EINVAL;
			if (c < ' ' || c == ':' || c == '\\' || c == '.')
				return -EINVAL;
			if (c >= 'A' && c <= 'Z' && conv == 's') return -EINVAL;
			space = c == ' ';
			*walk++ = c >= 'a' && c <= 'z' ? c-32 : c;
		}
		if (space) return -EINVAL;
		if (conv == 's' && len) return -EINVAL;
	}
	while (walk-res < MSDOS_NAME) *walk++ = ' ';
	for (reserved = reserved_names; *reserved; reserved++)
		if (!strncmp(res,*reserved,8)) return -EINVAL;
	return 0;
}


/* Locates a directory entry. */

static int msdos_find(struct inode *dir,const char *name,int len,
    struct buffer_head **bh,struct msdos_dir_entry **de,int *ino)
{
	char msdos_name[MSDOS_NAME];
	int res;

	if ((res = msdos_format_name(MSDOS_SB(dir->i_sb)->name_check,name,len,
	    msdos_name,1)) < 0) return res;
	return msdos_scan(dir,msdos_name,bh,de,ino);
}


int msdos_lookup(struct inode *dir,const char *name,int len,
    struct inode **result)
{
	int ino,res;
	struct msdos_dir_entry *de;
	struct buffer_head *bh;
	struct inode *next;

	*result = NULL;
	if (!dir) return -ENOENT;
	if (!S_ISDIR(dir->i_mode)) {
		iput(dir);
		return -ENOENT;
	}
	if (len == 1 && name[0] == '.') {
		*result = dir;
		return 0;
	}
	if (len == 2 && name[0] == '.' && name[1] == '.') {
		ino = msdos_parent_ino(dir,0);
		iput(dir);
		if (ino < 0) return ino;
		if (!(*result = iget(dir->i_sb,ino))) return -EACCES;
		return 0;
	}
	if ((res = msdos_find(dir,name,len,&bh,&de,&ino)) < 0) {
		iput(dir);
		return res;
	}
	if (bh) brelse(bh);
/* printk("lookup: ino=%d\n",ino); */
	if (!(*result = iget(dir->i_sb,ino))) {
		iput(dir);
		return -EACCES;
	}
	if (MSDOS_I(*result)->i_busy) { /* mkdir in progress */
		iput(*result);
		iput(dir);
		return -ENOENT;
	}
	while (MSDOS_I(*result)->i_old) {
		next = MSDOS_I(*result)->i_old;
		iput(*result);
		if (!(*result = iget(next->i_sb,next->i_ino))) {
			fs_panic(dir->i_sb,"msdos_lookup: Can't happen");
			iput(dir);
			return -ENOENT;
		}
	}
	iput(dir);
	return 0;
}


/* Creates a directory entry (name is already formatted). */

static int msdos_create_entry(struct inode *dir,char *name,int is_dir,
    struct inode **result)
{
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	int res,ino;

	if ((res = msdos_scan(dir,NULL,&bh,&de,&ino)) < 0) {
		if (res != -ENOENT) return res;
		if (dir->i_ino == MSDOS_ROOT_INO) return -ENOSPC;
		if ((res = msdos_add_cluster(dir)) < 0) return res;
		if ((res = msdos_scan(dir,NULL,&bh,&de,&ino)) < 0) return res;
	}
	/*
	 * XXX all times should be set by caller upon successful completion.
	 */
	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	dir->i_dirt = 1;
	memcpy(de->name,name,MSDOS_NAME);
	de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
	de->start = 0;
	date_unix2dos(dir->i_mtime,&de->time,&de->date);
	de->size = 0;
	bh->b_dirt = 1;
	if ((*result = iget(dir->i_sb,ino)) != NULL)
		msdos_read_inode(*result);
	brelse(bh);
	if (!*result) return -EIO;
	(*result)->i_mtime = (*result)->i_atime = (*result)->i_ctime =
	    CURRENT_TIME;
	(*result)->i_dirt = 1;
	return 0;
}


int msdos_create(struct inode *dir,const char *name,int len,int mode,
	struct inode **result)
{
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	char msdos_name[MSDOS_NAME];
	int ino,res;

	if (!dir) return -ENOENT;
	if ((res = msdos_format_name(MSDOS_SB(dir->i_sb)->name_check,name,len,
	    msdos_name,0)) < 0) {
		iput(dir);
		return res;
	}
	lock_creation();
	if (msdos_scan(dir,msdos_name,&bh,&de,&ino) >= 0) {
		unlock_creation();
		brelse(bh);
		iput(dir);
		return -EEXIST;
 	}
	res = msdos_create_entry(dir,msdos_name,S_ISDIR(mode),result);
	unlock_creation();
	iput(dir);
	return res;
}


#ifdef DEBUG

static void dump_fat(struct super_block *sb,int start)
{
	printk("[");
	while (start) {
		printk("%d ",start);
        	start = fat_access(sb,start,-1);
		if (!start) {
			printk("ERROR");
			break;
		}
		if (start == -1) break;
	}
	printk("]\n");
}

#endif


int msdos_mkdir(struct inode *dir,const char *name,int len,int mode)
{
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	struct inode *inode,*dot;
	char msdos_name[MSDOS_NAME];
	int ino,res;

	if ((res = msdos_format_name(MSDOS_SB(dir->i_sb)->name_check,name,len,
	    msdos_name,0)) < 0) {
		iput(dir);
		return res;
	}
	lock_creation();
	if (msdos_scan(dir,msdos_name,&bh,&de,&ino) >= 0) {
		unlock_creation();
		brelse(bh);
		iput(dir);
		return -EEXIST;
 	}
	if ((res = msdos_create_entry(dir,msdos_name,1,&inode)) < 0) {
		unlock_creation();
		iput(dir);
		return res;
	}
	dir->i_nlink++;
	inode->i_nlink = 2; /* no need to mark them dirty */
	MSDOS_I(inode)->i_busy = 1; /* prevent lookups */
	if ((res = msdos_add_cluster(inode)) < 0) goto mkdir_error;
	if ((res = msdos_create_entry(inode,MSDOS_DOT,1,&dot)) < 0)
		goto mkdir_error;
	dot->i_size = inode->i_size; /* doesn't grow in the 2nd create_entry */
	MSDOS_I(dot)->i_start = MSDOS_I(inode)->i_start;
	dot->i_nlink = inode->i_nlink;
	dot->i_dirt = 1;
	iput(dot);
	if ((res = msdos_create_entry(inode,MSDOS_DOTDOT,1,&dot)) < 0)
		goto mkdir_error;
	unlock_creation();
	dot->i_size = dir->i_size;
	MSDOS_I(dot)->i_start = MSDOS_I(dir)->i_start;
	dot->i_nlink = dir->i_nlink;
	dot->i_dirt = 1;
	MSDOS_I(inode)->i_busy = 0;
	iput(dot);
	iput(inode);
	iput(dir);
	return 0;
mkdir_error:
	iput(inode);
	if (msdos_rmdir(dir,name,len) < 0)
		fs_panic(dir->i_sb,"rmdir in mkdir failed");
	unlock_creation();
	return res;