namei.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

/*
 * linux/fs/ufs/namei.c
 *
 * Copyright (C) 1998
 * Daniel Pirkl <[e-mail]>
 * Charles University, Faculty of Mathematics and Physics
 *
 *  from
 *
 *  linux/fs/ext2/namei.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([e-mail])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/namei.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([e-mail]), 1995
 */

#include <asm/uaccess.h>

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/ufs_fs.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/locks.h>
#include <linux/quotaops.h>

#include "swab.h"
#include "util.h"

#undef UFS_NAMEI_DEBUG

#ifdef UFS_NAMEI_DEBUG
#define UFSD(x) printk("(%s, %d), %s: ", __FILE__, __LINE__, __FUNCTION__); printk x;
#else
#define UFSD(x)
#endif

/*
 * define how far ahead to read directories while searching them.
 */
#define NAMEI_RA_CHUNKS  2
#define NAMEI_RA_BLOCKS  4
#define NAMEI_RA_SIZE        (NAMEI_RA_CHUNKS * NAMEI_RA_BLOCKS)
#define NAMEI_RA_INDEX(c,b)  (((c) * NAMEI_RA_BLOCKS) + (b))

/*
 * NOTE! unlike strncmp, ufs_match returns 1 for success, 0 for failure.
 *
 * len <= UFS_MAXNAMLEN and de != NULL are guaranteed by caller.
 */
static inline int ufs_match (int len, const char * const name,
	struct ufs_dir_entry * de, unsigned flags, unsigned swab)
{
	if (len != ufs_get_de_namlen(de))
		return 0;
	if (!de->d_ino)
		return 0;
	return !memcmp(name, de->d_name, len);
}

/*
 *	ufs_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 * ufs_find_entry (struct inode * dir,
	const char * const name, int namelen, struct ufs_dir_entry ** res_dir)
{
	struct super_block * sb;
	struct buffer_head * bh_use[NAMEI_RA_SIZE];
	struct buffer_head * bh_read[NAMEI_RA_SIZE];
	unsigned long offset;
	int block, toread, i, err;
	unsigned flags, swab;

	UFSD(("ENTER, dir_ino %lu, name %s, namlen %u\n", dir->i_ino, name, namelen))
	
	*res_dir = NULL;
	
	sb = dir->i_sb;
	flags = sb->u.ufs_sb.s_flags;
	swab = sb->u.ufs_sb.s_swab;
	
	if (namelen > UFS_MAXNAMLEN)
		return NULL;

	memset (bh_use, 0, sizeof (bh_use));
	toread = 0;
	for (block = 0; block < NAMEI_RA_SIZE; ++block) {
		struct buffer_head * bh;

		if ((block << sb->s_blocksize_bits) >= dir->i_size)
			break;
		bh = ufs_getfrag (dir, block, 0, &err);
		bh_use[block] = bh;
		if (bh && !buffer_uptodate(bh))
			bh_read[toread++] = bh;
	}

	for (block = 0, offset = 0; offset < dir->i_size; block++) {
		struct buffer_head * bh;
		struct ufs_dir_entry * de;
		char * dlimit;

		if ((block % NAMEI_RA_BLOCKS) == 0 && toread) {
			ll_rw_block (READ, toread, bh_read);
			toread = 0;
		}
		bh = bh_use[block % NAMEI_RA_SIZE];
		if (!bh) {
			ufs_error (sb, "ufs_find_entry", 
				"directory #%lu contains a hole at offset %lu",
				dir->i_ino, offset);
			offset += sb->s_blocksize;
			continue;
		}
		wait_on_buffer (bh);
		if (!buffer_uptodate(bh)) {
			/*
			 * read error: all bets are off
			 */
			break;
		}

		de = (struct ufs_dir_entry *) bh->b_data;
		dlimit = bh->b_data + sb->s_blocksize;
		while ((char *) de < dlimit && offset < dir->i_size) {
			/* this code is executed quadratically often */
			/* do minimal checking by hand */
			int de_len;

			if ((char *) de + namelen <= dlimit &&
			    ufs_match (namelen, name, de, flags, swab)) {
				/* found a match -
				just to be sure, do a full check */
				if (!ufs_check_dir_entry("ufs_find_entry",
				    dir, de, bh, offset))
					goto failed;
				for (i = 0; i < NAMEI_RA_SIZE; ++i) {
					if (bh_use[i] != bh)
						brelse (bh_use[i]);
				}
				*res_dir = de;
				return bh;
			}
                        /* prevent looping on a bad block */
			de_len = SWAB16(de->d_reclen);
			if (de_len <= 0)
				goto failed;
			offset += de_len;
			de = (struct ufs_dir_entry *) ((char *) de + de_len);
		}

		brelse (bh);
		if (((block + NAMEI_RA_SIZE) << sb->s_blocksize_bits ) >=
		    dir->i_size)
			bh = NULL;
		else
			bh = ufs_getfrag (dir, block + NAMEI_RA_SIZE, 0, &err);
		bh_use[block % NAMEI_RA_SIZE] = bh;
		if (bh && !buffer_uptodate(bh))
			bh_read[toread++] = bh;
	}

failed:
	for (i = 0; i < NAMEI_RA_SIZE; ++i) brelse (bh_use[i]);
	UFSD(("EXIT\n"))
	return NULL;
}

static struct dentry *ufs_lookup(struct inode * dir, struct dentry *dentry)
{
	struct super_block * sb;
	struct inode * inode;
	struct ufs_dir_entry * de;
	struct buffer_head * bh;
	unsigned swab;
	
	UFSD(("ENTER\n"))
	
	sb = dir->i_sb;
	swab = sb->u.ufs_sb.s_swab;
	
	if (dentry->d_name.len > UFS_MAXNAMLEN)
		return ERR_PTR(-ENAMETOOLONG);

	bh = ufs_find_entry (dir, dentry->d_name.name, dentry->d_name.len, &de);
	inode = NULL;
	if (bh) {
		unsigned long ino = SWAB32(de->d_ino);
		brelse (bh);
		inode = iget(sb, ino);
		if (!inode) 
			return ERR_PTR(-EACCES);
	}
	d_add(dentry, inode);
	UFSD(("EXIT\n"))
	return NULL;
}

/*
 *	ufs_add_entry()
 *
 * adds a file entry to the specified directory, using the same
 * semantics as ufs_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 * ufs_add_entry (struct inode * dir,
	const char * name, int namelen, struct ufs_dir_entry ** res_dir, 
	int *err )
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	unsigned long offset;
	unsigned fragoff;
	unsigned short rec_len;
	struct buffer_head * bh;
	struct ufs_dir_entry * de, * de1;
	unsigned flags, swab;

	UFSD(("ENTER, name %s, namelen %u\n", name, namelen))
	
	*err = -EINVAL;
	*res_dir = NULL;
		
	sb = dir->i_sb;
	flags = sb->u.ufs_sb.s_flags;
	swab = sb->u.ufs_sb.s_swab;
	uspi = sb->u.ufs_sb.s_uspi;

	if (!namelen)
		return NULL;
	bh = ufs_bread (dir, 0, 0, err);
	if (!bh)
		return NULL;
	rec_len = UFS_DIR_REC_LEN(namelen);
	offset = 0;
	de = (struct ufs_dir_entry *) bh->b_data;
	*err = -ENOSPC;
	while (1) {
		if ((char *)de >= UFS_SECTOR_SIZE + bh->b_data) {
			fragoff = offset & ~uspi->s_fmask;
			if (fragoff != 0 && fragoff != UFS_SECTOR_SIZE)
				ufs_error (sb, "ufs_add_entry", "internal error"
					" fragoff %u", fragoff);
			if (!fragoff) {
				brelse (bh);
				bh = NULL;
				bh = ufs_bread (dir, offset >> sb->s_blocksize_bits, 1, err);
			}
			if (!bh)
				return NULL;
			if (dir->i_size <= offset) {
				if (dir->i_size == 0) {
					*err = -ENOENT;
					return NULL;
				}
				de = (struct ufs_dir_entry *) (bh->b_data + fragoff);
				de->d_ino = SWAB32(0);
				de->d_reclen = SWAB16(UFS_SECTOR_SIZE);
				ufs_set_de_namlen(de,0);
				dir->i_size = offset + UFS_SECTOR_SIZE;
				mark_inode_dirty(dir);
			} else {
				de = (struct ufs_dir_entry *) bh->b_data;
			}
		}
		if (!ufs_check_dir_entry ("ufs_add_entry", dir, de, bh, offset)) {
			*err = -ENOENT;
			brelse (bh);
			return NULL;
		}
		if (ufs_match (namelen, name, de, flags, swab)) {
				*err = -EEXIST;
				brelse (bh);
				return NULL;
		}
		if ((SWAB32(de->d_ino) == 0 && SWAB16(de->d_reclen) >= rec_len) ||
		    (SWAB16(de->d_reclen) >= UFS_DIR_REC_LEN(ufs_get_de_namlen(de)) + rec_len)) {
			offset += SWAB16(de->d_reclen);
			if (SWAB32(de->d_ino)) {
				de1 = (struct ufs_dir_entry *) ((char *) de +
					UFS_DIR_REC_LEN(ufs_get_de_namlen(de)));
				de1->d_reclen = SWAB16(SWAB16(de->d_reclen) -
					UFS_DIR_REC_LEN(ufs_get_de_namlen(de)));
				de->d_reclen = SWAB16(UFS_DIR_REC_LEN(ufs_get_de_namlen(de)));
				de = de1;
			}
			de->d_ino = SWAB32(0);
			ufs_set_de_namlen(de, namelen);
			memcpy (de->d_name, name, namelen + 1);
			/*
			 * XXX shouldn't update any times until successful
			 * completion of syscall, but too many callers depend
			 * on this.
			 *
			 * XXX similarly, too many callers depend on
			 * ufs_new_inode() setting the times, but error
			 * recovery deletes the inode, so the worst that can
			 * happen is that the times are slightly out of date
			 * and/or different from the directory change time.
			 */
			dir->i_mtime = dir->i_ctime = CURRENT_TIME;
			mark_inode_dirty(dir);
			dir->i_version = ++event;
			mark_buffer_dirty(bh);
			*res_dir = de;
			*err = 0;
			
			UFSD(("EXIT\n"))
			return bh;
		}
		offset += SWAB16(de->d_reclen);
		de = (struct ufs_dir_entry *) ((char *) de + SWAB16(de->d_reclen));
	}
	brelse (bh);
	UFSD(("EXIT (FAILED)\n"))
	return NULL;
}

/*
 * ufs_delete_entry deletes a directory entry by merging it with the
 * previous entry.
 */
static int ufs_delete_entry (struct inode * inode, struct ufs_dir_entry * dir,
	struct buffer_head * bh )
	
{
	struct super_block * sb;
	struct ufs_dir_entry * de, * pde;
	unsigned i;
	unsigned flags, swab;
	
	UFSD(("ENTER\n"))

	sb = inode->i_sb;
	flags = sb->u.ufs_sb.s_flags;
	swab = sb->u.ufs_sb.s_swab;
	i = 0;
	pde = NULL;
	de = (struct ufs_dir_entry *) bh->b_data;
	
	UFSD(("ino %u, reclen %u, namlen %u, name %s\n", SWAB32(de->d_ino),
		SWAB16(de->d_reclen), ufs_get_de_namlen(de), de->d_name))

	while (i < bh->b_size) {
		if (!ufs_check_dir_entry ("ufs_delete_entry", inode, de, bh, i))
			return -EIO;
		if (de == dir)  {
			if (pde)
				pde->d_reclen =
				    SWAB16(SWAB16(pde->d_reclen) +
				    SWAB16(dir->d_reclen));
			dir->d_ino = SWAB32(0);
			UFSD(("EXIT\n"))
			return 0;
		}
		i += SWAB16(de->d_reclen);
		if (i == UFS_SECTOR_SIZE) pde = NULL;
		else pde = de;
		de = (struct ufs_dir_entry *)
		    ((char *) de + SWAB16(de->d_reclen));
		if (i == UFS_SECTOR_SIZE && SWAB16(de->d_reclen) == 0)
			break;
	}
	UFSD(("EXIT\n"))
	return -ENOENT;
}

/*
 * By the time this is called, we already have created
 * the directory cache entry for the new file, but it
 * is so far negative - it has no inode.
 *
 * If the create succeeds, we fill in the inode information
 * with d_instantiate(). 
 */
static int ufs_create (struct inode * dir, struct dentry * dentry, int mode)
{
	struct super_block * sb;
	struct inode * inode;
	struct buffer_head * bh;
	struct ufs_dir_entry * de;
	int err = -EIO;
	unsigned flags, swab;
	
	sb = dir->i_sb;
	swab = sb->u.ufs_sb.s_swab;
	flags = sb->u.ufs_sb.s_flags;
	/*
	 * N.B. Several error exits in ufs_new_inode don't set err.
	 */
	UFSD(("ENTER\n"))
	
	inode = ufs_new_inode (dir, mode, &err);
	if (!inode)
		return err;
	inode->i_op = &ufs_file_inode_operations;
	inode->i_fop = &ufs_file_operations;
	inode->i_mapping->a_ops = &ufs_aops;
	inode->i_mode = mode;
	mark_inode_dirty(inode);
	bh = ufs_add_entry (dir, dentry->d_name.name, dentry->d_name.len, &de, &err);
	if (!bh) {
		inode->i_nlink--;
		mark_inode_dirty(inode);
		iput (inode);
		return err;
	}
	de->d_ino = SWAB32(inode->i_ino);
	ufs_set_de_type (de, inode->i_mode);
	dir->i_version = ++event;
	mark_buffer_dirty(bh);
	if (IS_SYNC(dir)) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
	brelse (bh);
	d_instantiate(dentry, inode);
	
	UFSD(("EXIT\n"))
	
	return 0;
}

static int ufs_mknod (struct inode * dir, struct dentry *dentry, int mode, int rdev)
{
	struct super_block * sb;
	struct inode * inode;
	struct buffer_head * bh;
	struct ufs_dir_entry * de;
	int err = -EIO;
	unsigned flags, swab;
	
	sb = dir->i_sb;
	flags = sb->u.ufs_sb.s_flags;
	swab = sb->u.ufs_sb.s_swab;

	inode = ufs_new_inode (dir, mode, &err);
	if (!inode)
		goto out;

	inode->i_uid = current->fsuid;
	init_special_inode(inode, mode, rdev);
	mark_inode_dirty(inode);
	bh = ufs_add_entry (dir, dentry->d_name.name, dentry->d_name.len, &de, &err);
	if (!bh)
		goto out_no_entry;
	de->d_ino = SWAB32(inode->i_ino);
	ufs_set_de_type (de, inode->i_mode);
	dir->i_version = ++event;
	mark_buffer_dirty(bh);
	if (IS_SYNC(dir)) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
	d_instantiate(dentry, inode);
	brelse(bh);
	err = 0;
out:
	return err;

out_no_entry:
	inode->i_nlink--;
	mark_inode_dirty(inode);
	iput(inode);
	goto out;
}

static int ufs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
{