namei.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

/*
 *  Linux/fs/xiafs/namei.c
 *
 *  Copyright (C) Q. Frank Xia, 1993.
 *  
 *  Based on Linus' minix/namei.c
 *  Copyright (C) Linus Torvalds, 1991, 1992.
 * 
 *  This software may be redistributed per Linux Copyright.
 */

#include <linux/sched.h>
#include <linux/xia_fs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/errno.h>
#include <asm/segment.h>

#include "xiafs_mac.h"

#define RNDUP4(x)	((3+(u_long)(x)) & ~3)
/*
 * ok, we cannot use strncmp, as the name is not in our data space.
 * Thus we'll have to use xiafs_match. No big problem. Match also makes
 * some sanity tests.
 *
 * NOTE! unlike strncmp, xiafs_match returns 1 for success, 0 for failure.
 */
static int xiafs_match(int len, const char * name, struct xiafs_direct * dep)
{
    int i;

    if (!dep || !dep->d_ino || len > _XIAFS_NAME_LEN)
        return 0;
    /* "" means "." ---> so paths like "/usr/lib//libc.a" work */
    if (!len && (dep->d_name[0]=='.') && (dep->d_name[1]=='\0'))
        return 1;
    if (len != dep->d_name_len)
        return 0;
    for (i=0; i < len; i++)
        if (*name++ != dep->d_name[i])
	    return 0;
    return 1;
}

/*
 *	xiafs_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the cache buffer in which the entry was found, and the entry
 * itself (as a parameter - res_dir). It does NOT read the inode of the
 * entry - you'll have to do that yourself if you want to.
 */
static struct buffer_head * 
xiafs_find_entry(struct inode * inode, const char * name, int namelen, 
	       struct xiafs_direct ** res_dir, struct xiafs_direct ** res_pre)
{
    int i, zones, pos;
    struct buffer_head * bh;
    struct xiafs_direct * dep, * dep_pre;

    *res_dir = NULL;
    if (!inode)
        return NULL;
    if (namelen > _XIAFS_NAME_LEN)
        return NULL;

    if (inode->i_size & (XIAFS_ZSIZE(inode->i_sb) - 1)) {
        printk("XIA-FS: bad dir size (%s %d)\n", WHERE_ERR);
	return NULL;
    }
    zones=inode->i_size >> XIAFS_ZSIZE_BITS(inode->i_sb);
    for (i=0; i < zones; i++ ) {
        bh = xiafs_bread(inode, i, 0);
	if (!bh)
	    continue;
	dep_pre=dep=(struct xiafs_direct *)bh->b_data;
	if (!i && (dep->d_rec_len != 12 || !dep->d_ino || 
		   dep->d_name_len != 1 || strcmp(dep->d_name, "."))) {
	    printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
	    brelse(bh);
	    return NULL;
	}
	pos = 0;
	while ( pos < XIAFS_ZSIZE(inode->i_sb) ) {
	    if (dep->d_ino > inode->i_sb->u.xiafs_sb.s_ninodes ||
		dep->d_rec_len < 12 || 
		dep->d_rec_len+(char *)dep > bh->b_data+XIAFS_ZSIZE(inode->i_sb) ||
		dep->d_name_len + 8 > dep->d_rec_len || dep->d_name_len <= 0 ||
		dep->d_name[dep->d_name_len] ) {
	        brelse(bh);
		return NULL;
	    }
	    if (xiafs_match(namelen, name, dep)) {
	        *res_dir=dep;
		if (res_pre) 
		    *res_pre=dep_pre;
		return bh;
	    }
	    pos += dep->d_rec_len;
	    dep_pre=dep;
	    dep=(struct xiafs_direct *)(bh->b_data + pos);
	}
	brelse(bh);
	if (pos > XIAFS_ZSIZE(inode->i_sb)) {
	    printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
	    return NULL;
	}
    }
    return NULL;
}

int xiafs_lookup(struct inode * dir, const char * name, int len,
	       struct inode ** result)
{
    int ino;
    struct xiafs_direct * dep;
    struct buffer_head * bh;

    *result = NULL;
    if (!dir)
        return -ENOENT;
    if (!S_ISDIR(dir->i_mode)) {
        iput(dir);
	return -ENOENT;
    }
    if (!(bh = xiafs_find_entry(dir, name, len, &dep, NULL))) {
        iput(dir);
	return -ENOENT;
    }
    ino = dep->d_ino;
    brelse(bh);
    if (!(*result = iget(dir->i_sb, ino))) {
        iput(dir);
	return -EACCES;
    }
    iput(dir);
    return 0;
}

/*
 *	xiafs_add_entry()
 *
 * adds a file entry to the specified directory, using the same
 * semantics as xiafs_find_entry(). It returns NULL if it failed.
 *
 * NOTE!! The inode part of 'de' is left at 0 - which means you
 * may not sleep between calling this and putting something into
 * the entry, as someone else might have used it while you slept.
 */
static struct buffer_head * xiafs_add_entry(struct inode * dir,
	const char * name, int namelen, struct xiafs_direct ** res_dir, 
	struct xiafs_direct ** res_pre)
{
    int i, pos, offset;
    struct buffer_head * bh;
    struct xiafs_direct * de, * de_pre;

    *res_dir = NULL;
    if (!dir || !namelen || namelen > _XIAFS_NAME_LEN)
        return NULL;

    if (dir->i_size & (XIAFS_ZSIZE(dir->i_sb) - 1)) {
        printk("XIA-FS: bad dir size (%s %d)\n", WHERE_ERR);
	return NULL;
    }
    pos=0;
    for ( ; ; ) {
        bh =  xiafs_bread(dir, pos >> XIAFS_ZSIZE_BITS(dir->i_sb), pos ? 1:0);
	if (!bh)
	    return NULL;
	de_pre=de=(struct xiafs_direct *)bh->b_data;
	if (!pos) {
	    if (de->d_rec_len != 12 || !de->d_ino || de->d_name_len != 1 ||
		strcmp(de->d_name, ".")) {
	        printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
		brelse(bh);
		return NULL;
	    }
	    offset = 12;
	    de_pre=de=(struct xiafs_direct *)(bh->b_data+12);
	} else
	    offset = 0;
	while (offset < XIAFS_ZSIZE(dir->i_sb)) {
	    if (pos >= dir->i_size) {
	        de->d_ino=0;
		de->d_name_len=0;
		de->d_name[0]=0;
		de->d_rec_len=XIAFS_ZSIZE(dir->i_sb);
		dir->i_size += XIAFS_ZSIZE(dir->i_sb);
		dir->i_dirt = 1;
	    } else {
	        if (de->d_ino > dir->i_sb->u.xiafs_sb.s_ninodes ||
		    de->d_rec_len < 12 || 
		    (char *)de+de->d_rec_len > bh->b_data+XIAFS_ZSIZE(dir->i_sb) ||
		    de->d_name_len + 8 > de->d_rec_len ||
		    de->d_name[de->d_name_len]) {
		    printk("XIA-FS: bad directory entry (%s %d)\n", WHERE_ERR);
		    brelse(bh);
		    return NULL;
		}
		if (de->d_ino &&
		    RNDUP4(de->d_name_len)+RNDUP4(namelen)+16<=de->d_rec_len) {
		    i=RNDUP4(de->d_name_len)+8;
		    de_pre=de;
		    de=(struct xiafs_direct *)(i+(u_char *)de_pre);
		    de->d_ino=0;
		    de->d_rec_len=de_pre->d_rec_len-i;
		    de_pre->d_rec_len=i;
		}
	    }
	    if (!de->d_ino && RNDUP4(namelen)+8 <= de->d_rec_len) {
		/*
		 * 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->d_name, name, namelen);
		de->d_name[namelen]=0;
		de->d_name_len=namelen;
		bh->b_dirt = 1;
		*res_dir = de;
		if (res_pre)
		    *res_pre = de_pre;
		return bh;
	    }
	    offset+=de->d_rec_len;
	    de_pre=de;
	    de=(struct xiafs_direct *)(bh->b_data+offset);
	}
	brelse(bh);
	if (offset > XIAFS_ZSIZE(dir->i_sb)) {
	    printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
	    return NULL;
	}
	pos+=XIAFS_ZSIZE(dir->i_sb);
    }
    return NULL;
}

int xiafs_create(struct inode * dir, const char * name, int len, int mode,
	struct inode ** result)
{
    struct inode * inode;
    struct buffer_head * bh;
    struct xiafs_direct * de;

    *result = NULL;
    if (!dir)
        return -ENOENT;
    inode = xiafs_new_inode(dir);
    if (!inode) {
        iput(dir);
	return -ENOSPC;
    }
    inode->i_op = &xiafs_file_inode_operations;
    inode->i_mode = mode;
    inode->i_dirt = 1;
    bh = xiafs_add_entry(dir, name, len, &de, NULL);
    if (!bh) {
        inode->i_nlink--;
	inode->i_dirt = 1;
	iput(inode);
	iput(dir);
	return -ENOSPC;
    }
    de->d_ino = inode->i_ino;
    bh->b_dirt = 1;
    brelse(bh);
    iput(dir);
    *result = inode;
    return 0;
}

int xiafs_mknod(struct inode *dir, const char *name, int len, int mode, int rdev)
{
    struct inode * inode;
    struct buffer_head * bh;
    struct xiafs_direct * de;

    if (!dir)
        return -ENOENT;
    bh = xiafs_find_entry(dir,name,len,&de, NULL);
    if (bh) {
        brelse(bh);
	iput(dir);
	return -EEXIST;
    }
    inode = xiafs_new_inode(dir);
    if (!inode) {
        iput(dir);
	return -ENOSPC;
    }
    inode->i_uid = current->euid;
    inode->i_mode = mode;
    inode->i_op = NULL;
    if (S_ISREG(inode->i_mode))
        inode->i_op = &xiafs_file_inode_operations;
    else if (S_ISDIR(inode->i_mode)) {
        inode->i_op = &xiafs_dir_inode_operations;
	if (dir->i_mode & S_ISGID)
	    inode->i_mode |= S_ISGID;
    }
    else if (S_ISLNK(inode->i_mode))
        inode->i_op = &xiafs_symlink_inode_operations;
    else if (S_ISCHR(inode->i_mode))
        inode->i_op = &chrdev_inode_operations;
    else if (S_ISBLK(inode->i_mode))
        inode->i_op = &blkdev_inode_operations;
    else if (S_ISFIFO(inode->i_mode))
    	init_fifo(inode);
    if (S_ISBLK(mode) || S_ISCHR(mode))
        inode->i_rdev = rdev;
    inode->i_atime = inode->i_ctime = inode->i_atime = CURRENT_TIME;
    inode->i_dirt = 1;
    bh = xiafs_add_entry(dir, name, len, &de, NULL);
    if (!bh) {
        inode->i_nlink--;
	inode->i_dirt = 1;
	iput(inode);
	iput(dir);
	return -ENOSPC;
    }
    de->d_ino = inode->i_ino;
    bh->b_dirt = 1;
    brelse(bh);
    iput(dir);
    iput(inode);
    return 0;
}

int xiafs_mkdir(struct inode * dir, const char * name, int len, int mode)
{
    struct inode * inode;
    struct buffer_head * bh, *dir_block;
    struct xiafs_direct * de;
	
    bh = xiafs_find_entry(dir,name,len,&de, NULL);
    if (bh) {
        brelse(bh);
	iput(dir);
	return -EEXIST;
    }
    if (dir->i_nlink > 64000) {
        iput(dir);
        return -EMLINK;
    }
    inode = xiafs_new_inode(dir);
    if (!inode) {
        iput(dir);
	return -ENOSPC;
    }
    inode->i_op = &xiafs_dir_inode_operations;
    inode->i_size = XIAFS_ZSIZE(dir->i_sb);
    inode->i_atime = inode->i_ctime = inode->i_mtime = CURRENT_TIME;
    dir_block = xiafs_bread(inode,0,1);
    if (!dir_block) {
        iput(dir);
	inode->i_nlink--;
	inode->i_dirt = 1;
	iput(inode);
	return -ENOSPC;
    }
    de = (struct xiafs_direct *) dir_block->b_data;
    de->d_ino=inode->i_ino;
    strcpy(de->d_name,".");
    de->d_name_len=1;
    de->d_rec_len=12;
    de =(struct xiafs_direct *)(12 + dir_block->b_data);
    de->d_ino = dir->i_ino;
    strcpy(de->d_name,"..");
    de->d_name_len=2;
    de->d_rec_len=XIAFS_ZSIZE(dir->i_sb)-12;
    inode->i_nlink = 2;
    dir_block->b_dirt = 1;
    brelse(dir_block);
    inode->i_mode = S_IFDIR | (mode & S_IRWXUGO & ~current->umask);
    if (dir->i_mode & S_ISGID)
        inode->i_mode |= S_ISGID;
    inode->i_dirt = 1;
    bh = xiafs_add_entry(dir, name, len, &de, NULL);
    if (!bh) {
        iput(dir);
	inode->i_nlink=0;
	iput(inode);
	return -ENOSPC;
    }
    de->d_ino = inode->i_ino;
    bh->b_dirt = 1;
    dir->i_nlink++;
    dir->i_dirt = 1;
    iput(dir);
    iput(inode);
    brelse(bh);
    return 0;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
static int empty_dir(struct inode * inode)
{
    int i, zones, offset;
    struct buffer_head * bh;
    struct xiafs_direct * de;

    if (inode->i_size & (XIAFS_ZSIZE(inode->i_sb)-1) ) {
        printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
	return 1;
    }

    zones=inode->i_size >> XIAFS_ZSIZE_BITS(inode->i_sb);
    for (i=0; i < zones; i++) {
        bh =  xiafs_bread(inode, i, 0);
	if (!i) {
	    if (!bh) {
	        printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
		return 1;
	    }
	    de=(struct xiafs_direct *)bh->b_data;
	    if (de->d_ino != inode->i_ino || strcmp(".", de->d_name) ||