namei.c

elinux jffs初始版本 具体了解JFFS的文件系统！

/*
 *  linux/fs/affs/namei.c
 *
 *  (c) 1996  Hans-Joachim Widmaier - Rewritten
 *
 *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 */

#include <linux/sched.h>
#include <linux/affs_fs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/locks.h>
#include <linux/amigaffs.h>
#include <asm/segment.h>

#include <linux/errno.h>

/* Simple toupper() for DOS\1 */

static inline unsigned int
affs_toupper(unsigned int ch)
{
	return ch >= 'a' && ch <= 'z' ? ch -= ('a' - 'A') : ch;
}

/* International toupper() for DOS\3 */

static inline unsigned int
affs_intl_toupper(unsigned int ch)
{
	return (ch >= 'a' && ch <= 'z') || (ch >= 0xE0
		&& ch <= 0xFE && ch != 0xF7) ?
		ch - ('a' - 'A') : ch;
}

/*
 * NOTE! unlike strncmp, affs_match returns 1 for success, 0 for failure.
 */

static int
affs_match(const char *name, int len, const char *compare, int dlen, int intl)
{
	if (!compare)
		return 0;

	if (len > 30)
		len = 30;
	if (dlen > 30)
		dlen = 30;

	/* "" means "." ---> so paths like "/usr/lib//libc.a" work */
	if (!len && dlen == 1 && compare[0] == '.')
		return 1;
	if (dlen != len)
		return 0;
	if (intl) {
		while (dlen--) {
			if (affs_intl_toupper(*name & 0xFF) != affs_intl_toupper(*compare & 0xFF))
				return 0;
			name++;
			compare++;
		}
	} else {
		while (dlen--) {
			if (affs_toupper(*name & 0xFF) != affs_toupper(*compare & 0xFF))
				return 0;
			name++;
			compare++;
		}
	}
	return 1;
}

int
affs_hash_name(const char *name, int len, int intl, int hashsize)
{
	unsigned int i, x;

	if (len > 30)
		len = 30;

	x = len;
	for (i = 0; i < len; i++)
		if (intl)
			x = (x * 13 + affs_intl_toupper(name[i] & 0xFF)) & 0x7ff;
		else
			x = (x * 13 + affs_toupper(name[i] & 0xFF)) & 0x7ff;

	return x % hashsize;
}

static struct buffer_head *
affs_find_entry(struct inode *dir, const char *name, int namelen,
		unsigned long *ino)
{
	struct buffer_head *bh;
	int	 intl;
	int	 key;

	pr_debug("AFFS: find_entry(%.*s)=\n",namelen,name);

	intl = AFFS_I2FSTYPE(dir);
	bh   = affs_bread(dir->i_dev,dir->i_ino,AFFS_I2BSIZE(dir));
	if (!bh)
		return NULL;

	if (affs_match(name,namelen,".",1,intl)) {
		*ino = dir->i_ino;
		return bh;
	}
	if (affs_match(name,namelen,"..",2,intl)) {
		*ino = affs_parent_ino(dir);
		return bh;
	}

	key = AFFS_GET_HASHENTRY(bh->b_data,affs_hash_name(name,namelen,intl,AFFS_I2HSIZE(dir)));

	for (;;) {
		char *cname;
		int cnamelen;

		affs_brelse(bh);
		if (key == 0) {
			bh = NULL;
			break;
		}
		bh = affs_bread(dir->i_dev,key,AFFS_I2BSIZE(dir));
		if (!bh)
			break;
		cnamelen = affs_get_file_name(AFFS_I2BSIZE(dir),bh->b_data,&cname);
		if (affs_match(name,namelen,cname,cnamelen,intl))
			break;
		key = htonl(FILE_END(bh->b_data,dir)->hash_chain);
	}
	*ino = key;
	return bh;
}

int
affs_lookup(struct inode *dir, const char *name, int len, struct inode **result)
{
	int res;
	unsigned long ino;
	struct buffer_head *bh;

	pr_debug("AFFS: lookup(%.*s)\n",len,name);

	*result = NULL;
	if (!dir)
		return -ENOENT;

	res = -ENOENT;
	if (S_ISDIR(dir->i_mode)) {
		if ((bh = affs_find_entry(dir,name,len,&ino))) {
			if (FILE_END(bh->b_data,dir)->original)
				ino = htonl(FILE_END(bh->b_data,dir)->original);
			affs_brelse(bh);
			if ((*result = iget(dir->i_sb,ino))) 
				res = 0;
			else
				res = -EACCES;
		}
	}
	iput(dir);
	return res;
}

int
affs_unlink(struct inode *dir, const char *name, int len)
{
	int			 retval;
	struct buffer_head	*bh;
	unsigned long		 ino;
	struct inode		*inode;

	pr_debug("AFFS: unlink(dir=%ld,\"%.*s\")\n",dir->i_ino,len,name);

	bh      = NULL;
	inode   = NULL;
	retval  = -ENOENT;
	if (!(bh = affs_find_entry(dir,name,len,&ino))) {
		goto unlink_done;
	}
	if (!(inode = iget(dir->i_sb,ino))) {
		goto unlink_done;
	}
	if (S_ISDIR(inode->i_mode)) {
		retval = -EPERM;
		goto unlink_done;
	}

	if ((retval = affs_fix_hash_pred(dir,affs_hash_name(name,len,AFFS_I2FSTYPE(dir),
					 AFFS_I2HSIZE(dir)) + 6,ino,
					 FILE_END(bh->b_data,dir)->hash_chain)))
		goto unlink_done;

	if ((retval = affs_fixup(bh,inode)))
		goto unlink_done;

	inode->i_nlink=0;
	inode->i_dirt=1;
	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	dir->i_version = ++event;
	dir->i_dirt=1;
unlink_done:
	affs_brelse(bh);
	iput(inode);
	iput(dir);
	return retval;
}

int
affs_create(struct inode *dir, const char *name, int len, int mode, struct inode **result)
{
	struct inode	*inode;
	int		 error;
	
	pr_debug("AFFS: create(%lu,\"%.*s\",0%o)\n",dir->i_ino,len,name,mode);


	*result = NULL;

	if (!dir || !dir->i_sb) {
		iput(dir);
		return -EINVAL;
	}
	inode = affs_new_inode(dir);
	if (!inode) {
		iput (dir);
		return -ENOSPC;
	}
	inode->i_mode = mode;
	if (dir->i_sb->u.affs_sb.s_flags & SF_OFS)
		inode->i_op = &affs_file_inode_operations_ofs;
	else
		inode->i_op = &affs_file_inode_operations;

	error = affs_add_entry(dir,NULL,inode,name,len,ST_FILE);
	if (error) {
		iput(dir);
		inode->i_nlink = 0;
		inode->i_dirt  = 1;
		iput(inode);
		return -ENOSPC;
	}
	inode->u.affs_i.i_protect = mode_to_prot(inode->i_mode);

	iput(dir);
	*result = inode;

	return 0;
}

int
affs_mkdir(struct inode *dir, const char *name, int len, int mode)
{
	struct inode		*inode;
	struct buffer_head	*bh;
	unsigned long		 i;
	int			 error;
	
	pr_debug("AFFS: mkdir(%lu,\"%.*s\",0%o)\n",dir->i_ino,len,name,mode);

	if (!dir || !dir->i_sb) {
		iput(dir);
		return -EINVAL;
	}
	bh = affs_find_entry(dir,name,len,&i);
	if (bh) {
		affs_brelse(bh);
		iput(dir);
		return -EEXIST;
	}
	inode = affs_new_inode(dir);
	if (!inode) {
		iput (dir);
		return -ENOSPC;
	}
	inode->i_op = &affs_dir_inode_operations;
	error       = affs_add_entry(dir,NULL,inode,name,len,ST_USERDIR);
	if (error) {
		iput(dir);
		inode->i_nlink = 0;
		inode->i_dirt  = 1;
		iput(inode);
		return error;
	}
	inode->i_mode = S_IFDIR | (mode & 0777 & ~current->fs->umask);
	inode->u.affs_i.i_protect = mode_to_prot(inode->i_mode);

	iput(dir);
	iput(inode);

	return 0;
}

static int
empty_dir(struct buffer_head *bh, int hashsize)
{
	while (--hashsize >= 0) {
		if (((struct dir_front *)bh->b_data)->hashtable[hashsize])
			return 0;
	}
	return 1;
}

int
affs_rmdir(struct inode *dir, const char *name, int len)
{
	int			 retval;
	unsigned long		 ino;
	struct inode		*inode;
	struct buffer_head	*bh;

	pr_debug("AFFS: rmdir(dir=%lu,\"%.*s\")\n",dir->i_ino,len,name);

	inode  = NULL;
	retval = -ENOENT;
	if (!(bh = affs_find_entry(dir,name,len,&ino))) {
		goto rmdir_done;
	}
	if (!(inode = iget(dir->i_sb,ino))) {
		goto rmdir_done;
	}
	retval = -EPERM;
        if (!fsuser() && current->fsuid != inode->i_uid &&
            current->fsuid != dir->i_uid)
		goto rmdir_done;
	if (inode->i_dev != dir->i_dev)
		goto rmdir_done;
	if (inode == dir)	/* we may not delete ".", but "../dir" is ok */
		goto rmdir_done;
	if (!S_ISDIR(inode->i_mode)) {
		retval = -ENOTDIR;
		goto rmdir_done;
	}
	if (!empty_dir(bh,AFFS_I2HSIZE(inode))) {
		retval = -ENOTEMPTY;
		goto rmdir_done;
	}
	if (inode->i_count > 1) {
		retval = -EBUSY;
		goto rmdir_done;
	}
	if ((retval = affs_fix_hash_pred(dir,affs_hash_name(name,len,AFFS_I2FSTYPE(dir),
					 AFFS_I2HSIZE(dir)) + 6,ino,
					 FILE_END(bh->b_data,dir)->hash_chain)))
		goto rmdir_done;

	if ((retval = affs_fixup(bh,inode)))
		goto rmdir_done;

	inode->i_nlink=0;
	inode->i_dirt=1;
	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	dir->i_version = ++event;
	dir->i_dirt=1;
rmdir_done:
	iput(dir);
	iput(inode);
	affs_brelse(bh);
	return retval;
}

int
affs_symlink(struct inode *dir, const char *name, int len, const char *symname)