namei.c

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/*
 *  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
 *  Directory entry file type support and forward compatibility hooks
 *  	for B-tree directories by Theodore Ts'o ([e-mail]), 1998
 */

#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include <linux/locks.h>
#include <linux/quotaops.h>



/*
 * 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, ext2_match returns 1 for success, 0 for failure.
 *
 * `len <= EXT2_NAME_LEN' is guaranteed by caller.
 * `de != NULL' is guaranteed by caller.
 */
static inline int ext2_match (int len, const char * const name,
		       struct ext2_dir_entry_2 * de)
{
	if (len != de->name_len)
		return 0;
	if (!de->inode)
		return 0;
	return !memcmp(name, de->name, len);
}

/*
 *	ext2_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 * ext2_find_entry (struct inode * dir,
					     const char * const name, int namelen,
					     struct ext2_dir_entry_2 ** 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;

	*res_dir = NULL;
	sb = dir->i_sb;

	if (namelen > EXT2_NAME_LEN)
		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 << EXT2_BLOCK_SIZE_BITS (sb)) >= dir->i_size)
			break;
		bh = ext2_getblk (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 ext2_dir_entry_2 * 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) {
#if 0
			ext2_error (sb, "ext2_find_entry",
				    "directory #%lu contains a hole at offset %lu",
				    dir->i_ino, offset);
#endif
			offset += sb->s_blocksize;
			continue;
		}
		wait_on_buffer (bh);
		if (!buffer_uptodate(bh)) {
			/*
			 * read error: all bets are off
			 */
			break;
		}

		de = (struct ext2_dir_entry_2 *) bh->b_data;
		dlimit = bh->b_data + sb->s_blocksize;
		while ((char *) de < dlimit) {
			/* this code is executed quadratically often */
			/* do minimal checking `by hand' */
			int de_len;

			if ((char *) de + namelen <= dlimit &&
			    ext2_match (namelen, name, de)) {
				/* found a match -
				   just to be sure, do a full check */
				if (!ext2_check_dir_entry("ext2_find_entry",
							  dir, de, bh, offset))
					goto failure;
				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 = le16_to_cpu(de->rec_len);
			if (de_len <= 0)
				goto failure;
			offset += de_len;
			de = (struct ext2_dir_entry_2 *)
				((char *) de + de_len);
		}

		brelse (bh);
		if (((block + NAMEI_RA_SIZE) << EXT2_BLOCK_SIZE_BITS (sb)) >=
		    dir->i_size)
			bh = NULL;
		else
			bh = ext2_getblk (dir, block + NAMEI_RA_SIZE, 0, &err);
		bh_use[block % NAMEI_RA_SIZE] = bh;
		if (bh && !buffer_uptodate(bh))
			bh_read[toread++] = bh;
	}

failure:
	for (i = 0; i < NAMEI_RA_SIZE; ++i)
		brelse (bh_use[i]);
	return NULL;
}

static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry)
{
	struct inode * inode;
	struct ext2_dir_entry_2 * de;
	struct buffer_head * bh;

	if (dentry->d_name.len > EXT2_NAME_LEN)
		return ERR_PTR(-ENAMETOOLONG);

	bh = ext2_find_entry (dir, dentry->d_name.name, dentry->d_name.len, &de);
	inode = NULL;
	if (bh) {
		unsigned long ino = le32_to_cpu(de->inode);
		brelse (bh);
		inode = iget(dir->i_sb, ino);

		if (!inode)
			return ERR_PTR(-EACCES);
	}
	d_add(dentry, inode);
	return NULL;
}

#define S_SHIFT 12
static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
	[S_IFREG >> S_SHIFT]	EXT2_FT_REG_FILE,
	[S_IFDIR >> S_SHIFT]	EXT2_FT_DIR,
	[S_IFCHR >> S_SHIFT]	EXT2_FT_CHRDEV,
	[S_IFBLK >> S_SHIFT]	EXT2_FT_BLKDEV,
	[S_IFIFO >> S_SHIFT]	EXT2_FT_FIFO,
	[S_IFSOCK >> S_SHIFT]	EXT2_FT_SOCK,
	[S_IFLNK >> S_SHIFT]	EXT2_FT_SYMLINK,
};

static inline void ext2_set_de_type(struct super_block *sb,
				struct ext2_dir_entry_2 *de,
				umode_t mode) {
	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
		de->file_type = ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
}

/*
 *	ext2_add_entry()
 *
 * adds a file entry to the specified directory.
 */
int ext2_add_entry (struct inode * dir, const char * name, int namelen,
		    struct inode *inode)
{
	unsigned long offset;
	unsigned short rec_len;
	struct buffer_head * bh;
	struct ext2_dir_entry_2 * de, * de1;
	struct super_block * sb;
	int	retval;

	sb = dir->i_sb;

	if (!namelen)
		return -EINVAL;
	bh = ext2_bread (dir, 0, 0, &retval);
	if (!bh)
		return retval;
	rec_len = EXT2_DIR_REC_LEN(namelen);
	offset = 0;
	de = (struct ext2_dir_entry_2 *) bh->b_data;
	while (1) {
		if ((char *)de >= sb->s_blocksize + bh->b_data) {
			brelse (bh);
			bh = NULL;
			bh = ext2_bread (dir, offset >> EXT2_BLOCK_SIZE_BITS(sb), 1, &retval);
			if (!bh)
				return retval;
			if (dir->i_size <= offset) {
				if (dir->i_size == 0) {
					return -ENOENT;
				}

				ext2_debug ("creating next block\n");

				de = (struct ext2_dir_entry_2 *) bh->b_data;
				de->inode = 0;
				de->rec_len = le16_to_cpu(sb->s_blocksize);
				dir->i_size = offset + sb->s_blocksize;
				dir->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;
				mark_inode_dirty(dir);
			} else {

				ext2_debug ("skipping to next block\n");

				de = (struct ext2_dir_entry_2 *) bh->b_data;
			}
		}
		if (!ext2_check_dir_entry ("ext2_add_entry", dir, de, bh,
					   offset)) {
			brelse (bh);
			return -ENOENT;
		}
		if (ext2_match (namelen, name, de)) {
				brelse (bh);
				return -EEXIST;
		}
		if ((le32_to_cpu(de->inode) == 0 && le16_to_cpu(de->rec_len) >= rec_len) ||
		    (le16_to_cpu(de->rec_len) >= EXT2_DIR_REC_LEN(de->name_len) + rec_len)) {
			offset += le16_to_cpu(de->rec_len);
			if (le32_to_cpu(de->inode)) {
				de1 = (struct ext2_dir_entry_2 *) ((char *) de +
					EXT2_DIR_REC_LEN(de->name_len));
				de1->rec_len = cpu_to_le16(le16_to_cpu(de->rec_len) -
					EXT2_DIR_REC_LEN(de->name_len));
				de->rec_len = cpu_to_le16(EXT2_DIR_REC_LEN(de->name_len));
				de = de1;
			}
			de->file_type = EXT2_FT_UNKNOWN;
			if (inode) {
				de->inode = cpu_to_le32(inode->i_ino);
				ext2_set_de_type(dir->i_sb, de, inode->i_mode);
			} else
				de->inode = 0;
			de->name_len = namelen;
			memcpy (de->name, name, namelen);
			/*
			 * 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
			 * ext2_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;
			dir->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;
			mark_inode_dirty(dir);
			dir->i_version = ++event;
			mark_buffer_dirty_inode(bh, dir);
			if (IS_SYNC(dir)) {
				ll_rw_block (WRITE, 1, &bh);
				wait_on_buffer (bh);
			}
			brelse(bh);
			return 0;
		}
		offset += le16_to_cpu(de->rec_len);
		de = (struct ext2_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
	}
	brelse (bh);
	return -ENOSPC;
}

/*
 * ext2_delete_entry deletes a directory entry by merging it with the
 * previous entry
 */
static int ext2_delete_entry (struct inode * dir,
			      struct ext2_dir_entry_2 * de_del,
			      struct buffer_head * bh)
{
	struct ext2_dir_entry_2 * de, * pde;
	int i;

	i = 0;
	pde = NULL;
	de = (struct ext2_dir_entry_2 *) bh->b_data;
	while (i < bh->b_size) {
		if (!ext2_check_dir_entry ("ext2_delete_entry", NULL, 
					   de, bh, i))
			return -EIO;
		if (de == de_del)  {
			if (pde)
				pde->rec_len =
					cpu_to_le16(le16_to_cpu(pde->rec_len) +
						    le16_to_cpu(de->rec_len));
			else
				de->inode = 0;
			dir->i_version = ++event;
			mark_buffer_dirty_inode(bh, dir);
			if (IS_SYNC(dir)) {
				ll_rw_block (WRITE, 1, &bh);
				wait_on_buffer (bh);
			}
			return 0;
		}
		i += le16_to_cpu(de->rec_len);
		pde = de;
		de = (struct ext2_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
	}
	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 ext2_create (struct inode * dir, struct dentry * dentry, int mode)
{
	struct inode * inode = ext2_new_inode (dir, mode);
	int err = PTR_ERR(inode);
	if (IS_ERR(inode))
		return err;

	inode->i_op = &ext2_file_inode_operations;
	inode->i_fop = &ext2_file_operations;
	inode->i_mapping->a_ops = &ext2_aops;
	inode->i_mode = mode;
	mark_inode_dirty(inode);
	err = ext2_add_entry (dir, dentry->d_name.name, dentry->d_name.len, 
			     inode);
	if (err) {
		inode->i_nlink--;
		mark_inode_dirty(inode);
		iput (inode);
		return err;
	}
	d_instantiate(dentry, inode);
	return 0;
}

static int ext2_mknod (struct inode * dir, struct dentry *dentry, int mode, int rdev)
{
	struct inode * inode = ext2_new_inode (dir, mode);
	int err = PTR_ERR(inode);

	if (IS_ERR(inode))
		return err;

	inode->i_uid = current->fsuid;
	init_special_inode(inode, mode, rdev);
	err = ext2_add_entry (dir, dentry->d_name.name, dentry->d_name.len, 
			     inode);
	if (err)
		goto out_no_entry;
	mark_inode_dirty(inode);
	d_instantiate(dentry, inode);
	return 0;

out_no_entry:
	inode->i_nlink--;
	mark_inode_dirty(inode);
	iput(inode);
	return err;
}

static int ext2_mkdir(struct inode * dir, struct dentry * dentry, int mode)
{
	struct inode * inode;