add directory kernel

kernel/0.95/linux-0.95/fs/minix/namei.c

@@ -0,0 +1,795 @@
+/*
+ *  linux/fs/minix/namei.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <linux/sched.h>
+#include <linux/minix_fs.h>
+#include <linux/kernel.h>
+#include <asm/segment.h>
+
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <const.h>
+#include <sys/stat.h>
+
+extern int permission(struct inode * inode,int mask);
+extern struct inode * _namei(const char * filename, struct inode * base,
+	int follow_links);
+
+/*
+ * comment out this line if you want names > MINIX_NAME_LEN chars to be
+ * truncated. Else they will be disallowed.
+ */
+/* #define NO_TRUNCATE */
+
+/*
+ * ok, we cannot use strncmp, as the name is not in our data space.
+ * Thus we'll have to use minix_match. No big problem. Match also makes
+ * some sanity tests.
+ *
+ * NOTE! unlike strncmp, minix_match returns 1 for success, 0 for failure.
+ */
+static int minix_match(int len,const char * name,struct minix_dir_entry * de)
+{
+	register int same __asm__("ax");
+
+	if (!de || !de->inode || len > MINIX_NAME_LEN)
+		return 0;
+	/* "" means "." ---> so paths like "/usr/lib//libc.a" work */
+	if (!len && (de->name[0]=='.') && (de->name[1]=='\0'))
+		return 1;
+	if (len < MINIX_NAME_LEN && de->name[len])
+		return 0;
+	__asm__("cld\n\t"
+		"fs ; repe ; cmpsb\n\t"
+		"setz %%al"
+		:"=a" (same)
+		:"0" (0),"S" ((long) name),"D" ((long) de->name),"c" (len)
+		:"cx","di","si");
+	return same;
+}
+
+/*
+ *	minix_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 * minix_find_entry(struct inode * dir,
+	const char * name, int namelen, struct minix_dir_entry ** res_dir)
+{
+	int entries;
+	int block,i;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	*res_dir = NULL;
+	if (!dir)
+		return NULL;
+#ifdef NO_TRUNCATE
+	if (namelen > MINIX_NAME_LEN)
+		return NULL;
+#else
+	if (namelen > MINIX_NAME_LEN)
+		namelen = MINIX_NAME_LEN;
+#endif
+	entries = dir->i_size / (sizeof (struct minix_dir_entry));
+	if (!(block = dir->i_data[0]))
+		return NULL;
+	if (!(bh = bread(dir->i_dev,block)))
+		return NULL;
+	i = 0;
+	de = (struct minix_dir_entry *) bh->b_data;
+	while (i < entries) {
+		if ((char *)de >= BLOCK_SIZE+bh->b_data) {
+			brelse(bh);
+			bh = NULL;
+			if (!(block = bmap(dir,i/MINIX_DIR_ENTRIES_PER_BLOCK)) ||
+			    !(bh = bread(dir->i_dev,block))) {
+				i += MINIX_DIR_ENTRIES_PER_BLOCK;
+				continue;
+			}
+			de = (struct minix_dir_entry *) bh->b_data;
+		}
+		if (minix_match(namelen,name,de)) {
+			*res_dir = de;
+			return bh;
+		}
+		de++;
+		i++;
+	}
+	brelse(bh);
+	return NULL;
+}
+
+struct inode * minix_follow_link(struct inode * dir, struct inode * inode)
+{
+	unsigned short fs;
+	struct buffer_head * bh;
+
+	if (!dir) {
+		dir = current->root;
+		dir->i_count++;
+	}
+	if (!inode) {
+		iput(dir);
+		return NULL;
+	}
+	if (!S_ISLNK(inode->i_mode)) {
+		iput(dir);
+		return inode;
+	}
+	__asm__("mov %%fs,%0":"=r" (fs));
+	if ((current->link_count > 5) || !inode->i_data[0] ||
+	   !(bh = bread(inode->i_dev, inode->i_data[0]))) {
+		iput(dir);
+		iput(inode);
+		return NULL;
+	}
+	iput(inode);
+	__asm__("mov %0,%%fs"::"r" ((unsigned short) 0x10));
+	current->link_count++;
+	inode = _namei(bh->b_data,dir,1);
+	current->link_count--;
+	__asm__("mov %0,%%fs"::"r" (fs));
+	brelse(bh);
+	return inode;
+}
+
+int minix_lookup(struct inode * dir,const char * name, int len,
+	struct inode ** result)
+{
+	int ino;
+	struct minix_dir_entry * de;
+	struct buffer_head * bh;
+
+	*result = NULL;
+	if (!dir)
+		return -ENOENT;
+	if (!S_ISDIR(dir->i_mode)) {
+		iput(dir);
+		return -ENOENT;
+	}
+	if (!(bh = minix_find_entry(dir,name,len,&de))) {
+		iput(dir);
+		return -ENOENT;
+	}
+	ino = de->inode;
+	brelse(bh);
+	if (!(*result = iget(dir->i_dev,ino))) {
+		iput(dir);
+		return -EACCES;
+	}
+	iput(dir);
+	return 0;
+}
+
+/*
+ *	minix_add_entry()
+ *
+ * adds a file entry to the specified directory, using the same
+ * semantics as minix_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 * minix_add_entry(struct inode * dir,
+	const char * name, int namelen, struct minix_dir_entry ** res_dir)
+{
+	int block,i;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	*res_dir = NULL;
+	if (!dir)
+		return NULL;
+#ifdef NO_TRUNCATE
+	if (namelen > MINIX_NAME_LEN)
+		return NULL;
+#else
+	if (namelen > MINIX_NAME_LEN)
+		namelen = MINIX_NAME_LEN;
+#endif
+	if (!namelen)
+		return NULL;
+	if (!(block = dir->i_data[0]))
+		return NULL;
+	if (!(bh = bread(dir->i_dev,block)))
+		return NULL;
+	i = 0;
+	de = (struct minix_dir_entry *) bh->b_data;
+	while (1) {
+		if ((char *)de >= BLOCK_SIZE+bh->b_data) {
+			brelse(bh);
+			bh = NULL;
+			block = minix_create_block(dir,i/MINIX_DIR_ENTRIES_PER_BLOCK);
+			if (!block)
+				return NULL;
+			if (!(bh = bread(dir->i_dev,block))) {
+				i += MINIX_DIR_ENTRIES_PER_BLOCK;
+				continue;
+			}
+			de = (struct minix_dir_entry *) bh->b_data;
+		}
+		if (i*sizeof(struct minix_dir_entry) >= dir->i_size) {
+			de->inode=0;
+			dir->i_size = (i+1)*sizeof(struct minix_dir_entry);
+			dir->i_dirt = 1;
+			dir->i_ctime = CURRENT_TIME;
+		}
+		if (!de->inode) {
+			dir->i_mtime = CURRENT_TIME;
+			for (i=0; i < MINIX_NAME_LEN ; i++)
+				de->name[i]=(i<namelen)?get_fs_byte(name+i):0;
+			bh->b_dirt = 1;
+			*res_dir = de;
+			return bh;
+		}
+		de++;
+		i++;
+	}
+	brelse(bh);
+	return NULL;
+}
+
+int minix_create(struct inode * dir,const char * name, int len, int mode,
+	struct inode ** result)
+{
+	struct inode * inode;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	*result = NULL;
+	if (!dir)
+		return -ENOENT;
+	inode = minix_new_inode(dir->i_dev);
+	if (!inode) {
+		iput(dir);
+		return -ENOSPC;
+	}
+	inode->i_mode = mode;
+	inode->i_dirt = 1;
+	bh = minix_add_entry(dir,name,len,&de);
+	if (!bh) {
+		inode->i_nlink--;
+		iput(inode);
+		iput(dir);
+		return -ENOSPC;
+	}
+	de->inode = inode->i_ino;
+	bh->b_dirt = 1;
+	brelse(bh);
+	iput(dir);
+	*result = inode;
+	return 0;
+}
+
+int minix_mknod(struct inode * dir, const char * name, int len, int mode, int rdev)
+{
+	struct inode * inode;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	if (!dir)
+		return -ENOENT;
+	bh = minix_find_entry(dir,name,len,&de);
+	if (bh) {
+		brelse(bh);
+		iput(dir);
+		return -EEXIST;
+	}
+	inode = minix_new_inode(dir->i_dev);
+	if (!inode) {
+		iput(dir);
+		return -ENOSPC;
+	}
+	inode->i_uid = current->euid;
+	inode->i_mode = mode;
+	if (S_ISBLK(mode) || S_ISCHR(mode))
+		inode->i_rdev = rdev;
+	inode->i_mtime = inode->i_atime = CURRENT_TIME;
+	inode->i_dirt = 1;
+	bh = minix_add_entry(dir,name,len,&de);
+	if (!bh) {
+		inode->i_nlink--;
+		iput(inode);
+		iput(dir);
+		return -ENOSPC;
+	}
+	de->inode = inode->i_ino;
+	bh->b_dirt = 1;
+	brelse(bh);
+	iput(dir);
+	iput(inode);
+	return 0;
+}
+
+int minix_mkdir(struct inode * dir, const char * name, int len, int mode)
+{
+	struct inode * inode;
+	struct buffer_head * bh, *dir_block;
+	struct minix_dir_entry * de;
+	
+	bh = minix_find_entry(dir,name,len,&de);
+	if (bh) {
+		brelse(bh);
+		iput(dir);
+		return -EEXIST;
+	}
+	inode = minix_new_inode(dir->i_dev);
+	if (!inode) {
+		iput(dir);
+		return -ENOSPC;
+	}
+	inode->i_size = 32;
+	inode->i_dirt = 1;
+	inode->i_mtime = inode->i_atime = CURRENT_TIME;
+	if (!(inode->i_data[0] = minix_new_block(inode->i_dev))) {
+		iput(dir);
+		inode->i_nlink--;
+		iput(inode);
+		return -ENOSPC;
+	}
+	inode->i_dirt = 1;
+	if (!(dir_block = bread(inode->i_dev,inode->i_data[0]))) {
+		iput(dir);
+		inode->i_nlink--;
+		iput(inode);
+		return -ERROR;
+	}
+	de = (struct minix_dir_entry *) dir_block->b_data;
+	de->inode=inode->i_ino;
+	strcpy(de->name,".");
+	de++;
+	de->inode = dir->i_ino;
+	strcpy(de->name,"..");
+	inode->i_nlink = 2;
+	dir_block->b_dirt = 1;
+	brelse(dir_block);
+	inode->i_mode = I_DIRECTORY | (mode & 0777 & ~current->umask);
+	inode->i_dirt = 1;
+	bh = minix_add_entry(dir,name,len,&de);
+	if (!bh) {
+		iput(dir);
+		inode->i_nlink=0;
+		iput(inode);
+		return -ENOSPC;
+	}
+	de->inode = 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 nr,block;
+	int len;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	len = inode->i_size / sizeof (struct minix_dir_entry);
+	if (len<2 || !inode->i_data[0] ||
+	    !(bh=bread(inode->i_dev,inode->i_data[0]))) {
+	    	printk("warning - bad directory on dev %04x\n",inode->i_dev);
+		return 0;
+	}
+	de = (struct minix_dir_entry *) bh->b_data;
+	if (de[0].inode != inode->i_ino || !de[1].inode || 
+	    strcmp(".",de[0].name) || strcmp("..",de[1].name)) {
+	    	printk("warning - bad directory on dev %04x\n",inode->i_dev);
+		return 0;
+	}
+	nr = 2;
+	de += 2;
+	while (nr<len) {
+		if ((void *) de >= (void *) (bh->b_data+BLOCK_SIZE)) {
+			brelse(bh);
+			block=bmap(inode,nr/MINIX_DIR_ENTRIES_PER_BLOCK);
+			if (!block) {
+				nr += MINIX_DIR_ENTRIES_PER_BLOCK;
+				continue;
+			}
+			if (!(bh=bread(inode->i_dev,block)))
+				return 0;
+			de = (struct minix_dir_entry *) bh->b_data;
+		}
+		if (de->inode) {
+			brelse(bh);
+			return 0;
+		}
+		de++;
+		nr++;
+	}
+	brelse(bh);
+	return 1;
+}
+
+int minix_rmdir(struct inode * dir, const char * name, int len)
+{
+	int retval;
+	struct inode * inode;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	inode = NULL;
+	bh = minix_find_entry(dir,name,len,&de);
+	retval = -ENOENT;
+	if (!bh)
+		goto end_rmdir;
+	retval = -EPERM;
+	if (!(inode = iget(dir->i_dev, de->inode)))
+		goto end_rmdir;
+	if ((dir->i_mode & S_ISVTX) && current->euid &&
+	   inode->i_uid != current->euid)
+		goto end_rmdir;
+	if (inode->i_dev != dir->i_dev)
+		goto end_rmdir;
+	if (inode == dir)	/* we may not delete ".", but "../dir" is ok */
+		goto end_rmdir;
+	if (!S_ISDIR(inode->i_mode)) {
+		retval = -ENOTDIR;
+		goto end_rmdir;
+	}
+	if (!empty_dir(inode)) {
+		retval = -ENOTEMPTY;
+		goto end_rmdir;
+	}
+	if (inode->i_count > 1) {
+		retval = -EBUSY;
+		goto end_rmdir;
+	}
+	if (inode->i_nlink != 2)
+		printk("empty directory has nlink!=2 (%d)\n",inode->i_nlink);
+	de->inode = 0;
+	bh->b_dirt = 1;
+	inode->i_nlink=0;
+	inode->i_dirt=1;
+	dir->i_nlink--;
+	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+	dir->i_dirt=1;
+	retval = 0;
+end_rmdir:
+	iput(dir);
+	iput(inode);
+	brelse(bh);
+	return retval;
+}
+
+int minix_unlink(struct inode * dir, const char * name, int len)
+{
+	int retval;
+	struct inode * inode;
+	struct buffer_head * bh;
+	struct minix_dir_entry * de;
+
+	retval = -ENOENT;
+	inode = NULL;
+	bh = minix_find_entry(dir,name,len,&de);
+	if (!bh)
+		goto end_unlink;
+	if (!(inode = iget(dir->i_dev, de->inode)))
+		goto end_unlink;
+	retval = -EPERM;
+	if ((dir->i_mode & S_ISVTX) && !suser() &&
+	    current->euid != inode->i_uid &&
+	    current->euid != dir->i_uid)
+		goto end_unlink;
+	if (S_ISDIR(inode->i_mode))
+		goto end_unlink;
+	if (!inode->i_nlink) {
+		printk("Deleting nonexistent file (%04x:%d), %d\n",
+			inode->i_dev,inode->i_ino,inode->i_nlink);
+		inode->i_nlink=1;
+	}
+	de->inode = 0;
+	bh->b_dirt = 1;
+	inode->i_nlink--;
+	inode->i_dirt = 1;
+	inode->i_ctime = CURRENT_TIME;
+	retval = 0;
+end_unlink:
+	brelse(bh);
+	iput(inode);
+	iput(dir);
+	return retval;
+}
+
+int minix_symlink(struct inode * dir, const char * name, int len, const char * symname)
+{
+	struct minix_dir_entry * de;
+	struct inode * inode = NULL;
+	struct buffer_head * bh = NULL, * name_block = NULL;
+	int i;
+	char c;
+
+	if (!(inode = minix_new_inode(dir->i_dev))) {
+		iput(dir);
+		return -ENOSPC;
+	}
+	inode->i_mode = S_IFLNK | 0777;
+	inode->i_dirt = 1;
+	if (!(inode->i_data[0] = minix_new_block(inode->i_dev))) {
+		iput(dir);
+		inode->i_nlink--;
+		iput(inode);
+		return -ENOSPC;
+	}
+	inode->i_dirt = 1;
+	if (!(name_block = bread(inode->i_dev,inode->i_data[0]))) {
+		iput(dir);
+		inode->i_nlink--;
+		iput(inode);
+		return -ERROR;
+	}
+	i = 0;
+	while (i < 1023 && (c=get_fs_byte(symname++)))
+		name_block->b_data[i++] = c;
+	name_block->b_data[i] = 0;
+	name_block->b_dirt = 1;
+	brelse(name_block);
+	inode->i_size = i;
+	inode->i_dirt = 1;
+	bh = minix_find_entry(dir,name,len,&de);
+	if (bh) {
+		inode->i_nlink--;
+		iput(inode);
+		brelse(bh);
+		iput(dir);
+		return -EEXIST;
+	}
+	bh = minix_add_entry(dir,name,len,&de);
+	if (!bh) {
+		inode->i_nlink--;
+		iput(inode);
+		iput(dir);
+		return -ENOSPC;
+	}
+	de->inode = inode->i_ino;
+	bh->b_dirt = 1;
+	brelse(bh);
+	iput(dir);
+	iput(inode);
+	return 0;
+}
+
+int minix_link(struct inode * oldinode, struct inode * dir, const char * name, int len)
+{
+	struct minix_dir_entry * de;
+	struct buffer_head * bh;
+
+	if (S_ISDIR(oldinode->i_mode)) {
+		iput(oldinode);
+		iput(dir);
+		return -EPERM;
+	}
+	bh = minix_find_entry(dir,name,len,&de);
+	if (bh) {
+		brelse(bh);
+		iput(dir);
+		iput(oldinode);
+		return -EEXIST;
+	}
+	bh = minix_add_entry(dir,name,len,&de);
+	if (!bh) {
+		iput(dir);
+		iput(oldinode);
+		return -ENOSPC;
+	}
+	de->inode = oldinode->i_ino;
+	bh->b_dirt = 1;
+	brelse(bh);
+	iput(dir);
+	oldinode->i_nlink++;
+	oldinode->i_ctime = CURRENT_TIME;
+	oldinode->i_dirt = 1;
+	iput(oldinode);
+	return 0;
+}
+
+static int subdir(struct inode * new, struct inode * old)
+{
+	unsigned short fs;
+	int ino;
+	int result;
+
+	__asm__("mov %%fs,%0":"=r" (fs));
+	__asm__("mov %0,%%fs"::"r" ((unsigned short) 0x10));
+	new->i_count++;
+	result = 0;
+	for (;;) {
+		if (new == old) {
+			result = 1;
+			break;
+		}
+		if (new->i_dev != old->i_dev)
+			break;
+		ino = new->i_ino;
+		if (minix_lookup(new,"..",2,&new))
+			break;
+		if (new->i_ino == ino)
+			break;
+	}
+	iput(new);
+	__asm__("mov %0,%%fs"::"r" (fs));
+	return result;
+}
+
+#define PARENT_INO(buffer) \
+(((struct minix_dir_entry *) (buffer))[1].inode)
+
+#define PARENT_NAME(buffer) \
+(((struct minix_dir_entry *) (buffer))[1].name)
+
+/*
+ * rename uses retrying to avoid race-conditions: at least they should be minimal.
+ * it tries to allocate all the blocks, then sanity-checks, and if the sanity-
+ * checks fail, it tries to restart itself again. Very practical - no changes
+ * are done until we know everything works ok.. and then all the changes can be
+ * done in one fell swoop when we have claimed all the buffers needed.
+ *
+ * Anybody can rename anything with this: the permission checks are left to the
+ * higher-level routines.
+ */
+static int do_minix_rename(struct inode * old_dir, const char * old_name, int old_len,
+	struct inode * new_dir, const char * new_name, int new_len)
+{
+	struct inode * old_inode, * new_inode;
+	struct buffer_head * old_bh, * new_bh, * dir_bh;
+	struct minix_dir_entry * old_de, * new_de;
+	int retval;
+
+	goto start_up;
+try_again:
+	brelse(old_bh);
+	brelse(new_bh);
+	brelse(dir_bh);
+	iput(old_inode);
+	iput(new_inode);
+	current->counter = 0;
+	schedule();
+start_up:
+	old_inode = new_inode = NULL;
+	old_bh = new_bh = dir_bh = NULL;
+	old_bh = minix_find_entry(old_dir,old_name,old_len,&old_de);
+	retval = -ENOENT;
+	if (!old_bh)
+		goto end_rename;
+	old_inode = iget(old_dir->i_dev, old_de->inode);
+	if (!old_inode)
+		goto end_rename;
+	new_bh = minix_find_entry(new_dir,new_name,new_len,&new_de);
+	if (new_bh) {
+		new_inode = iget(new_dir->i_dev, new_de->inode);
+		if (!new_inode) {
+			brelse(new_bh);
+			new_bh = NULL;
+		}
+	}
+	if (new_inode == old_inode) {
+		retval = 0;
+		goto end_rename;
+	}
+	if (S_ISDIR(old_inode->i_mode)) {
+		retval = -EEXIST;
+		if (new_bh)
+			goto end_rename;
+		retval = -EACCES;
+		if (!permission(old_inode, MAY_WRITE))
+			goto end_rename;
+		retval = -EINVAL;
+		if (subdir(new_dir, old_inode))
+			goto end_rename;
+		retval = -EIO;
+		if (!old_inode->i_data[0])
+			goto end_rename;
+		if (!(dir_bh = bread(old_inode->i_dev, old_inode->i_data[0])))
+			goto end_rename;
+		if (PARENT_INO(dir_bh->b_data) != old_dir->i_ino)
+			goto end_rename;
+	}
+	if (!new_bh)
+		new_bh = minix_add_entry(new_dir,new_name,new_len,&new_de);
+	retval = -ENOSPC;
+	if (!new_bh)
+		goto end_rename;
+/* sanity checking before doing the rename - avoid races */
+	if (new_inode && (new_de->inode != new_inode->i_ino))
+		goto try_again;
+	if (new_de->inode && !new_inode)
+		goto try_again;
+	if (old_de->inode != old_inode->i_ino)
+		goto try_again;
+/* ok, that's it */
+	old_de->inode = 0;
+	new_de->inode = old_inode->i_ino;
+	if (new_inode)
+		new_inode->i_nlink--;
+	old_bh->b_dirt = 1;
+	new_bh->b_dirt = 1;
+	if (dir_bh) {
+		PARENT_INO(dir_bh->b_data) = new_dir->i_ino;
+		dir_bh->b_dirt = 1;
+		old_dir->i_nlink--;
+		new_dir->i_nlink++;
+		old_dir->i_dirt = 1;
+		new_dir->i_dirt = 1;
+	}
+	retval = 0;
+end_rename:
+	brelse(dir_bh);
+	brelse(old_bh);
+	brelse(new_bh);
+	iput(old_inode);
+	iput(new_inode);
+	iput(old_dir);
+	iput(new_dir);
+	return retval;
+}
+
+/*
+ * Ok, rename also locks out other renames, as they can change the parent of
+ * a directory, and we don't want any races. Other races are checked for by
+ * "do_rename()", which restarts if there are inconsistencies.
+ *
+ * Note that there is no race between different filesystems: it's only within
+ * the same device that races occur: many renames can happen at once, as long
+ * as they are on different partitions.
+ */
+int minix_rename(struct inode * old_dir, const char * old_name, int old_len,
+	struct inode * new_dir, const char * new_name, int new_len)
+{
+	static struct task_struct * wait = NULL;
+	static int lock = 0;
+	int result;
+
+	while (lock)
+		sleep_on(&wait);
+	lock = 1;
+	result = do_minix_rename(old_dir, old_name, old_len,
+		new_dir, new_name, new_len);
+	lock = 0;
+	wake_up(&wait);
+	return result;
+}
+
+int minix_readlink(struct inode * inode, char * buffer, int buflen)
+{
+	struct buffer_head * bh;
+	int i;
+	char c;
+
+	if (!S_ISLNK(inode->i_mode)) {
+		iput(inode);
+		return -EINVAL;
+	}
+	if (buflen > 1023)
+		buflen = 1023;
+	if (inode->i_data[0])
+		bh = bread(inode->i_dev, inode->i_data[0]);
+	else
+		bh = NULL;
+	iput(inode);
+	if (!bh)
+		return 0;
+	i = 0;
+	while (i<buflen && (c = bh->b_data[i])) {
+		i++;
+		put_fs_byte(c,buffer++);
+	}
+	brelse(bh);
+	return i;
+}