C++ dbstart函数代码示例

/* like interpose above, but for an already existing dentry */
void unionfs_reinterpose(struct dentry *dentry)
{
    struct dentry *lower_dentry;
    struct inode *inode;
    int bindex, bstart, bend;

    verify_locked(dentry);

    /* This is pre-allocated inode */
    inode = dentry->d_inode;

    bstart = dbstart(dentry);
    bend = dbend(dentry);
    for (bindex = bstart; bindex <= bend; bindex++) {
        lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
        if (!lower_dentry)
            continue;

        if (!lower_dentry->d_inode)
            continue;
        if (unionfs_lower_inode_idx(inode, bindex))
            continue;
        unionfs_set_lower_inode_idx(inode, bindex,
                                    igrab(lower_dentry->d_inode));
    }
    ibstart(inode) = dbstart(dentry);
    ibend(inode) = dbend(dentry);
}

/* set lower dentry ptr and update bstart & bend if necessary */
static void __set_dentry(struct dentry *upper, struct dentry *lower,
			 int bindex)
{
	unionfs_set_lower_dentry_idx(upper, bindex, lower);
	if (likely(dbstart(upper) > bindex))
		dbstart(upper) = bindex;
	if (likely(dbend(upper) < bindex))
		dbend(upper) = bindex;
}

/*
 * return to user-space the branch indices containing the file in question
 *
 * We use fd_set and therefore we are limited to the number of the branches
 * to FD_SETSIZE, which is currently 1024 - plenty for most people
 */
static int unionfs_ioctl_queryfile(struct file *file, struct dentry *parent,
				   unsigned int cmd, unsigned long arg)
{
	int err = 0;
	fd_set branchlist;
	int bstart = 0, bend = 0, bindex = 0;
	int orig_bstart, orig_bend;
	struct dentry *dentry, *lower_dentry;
	struct vfsmount *mnt;

	dentry = file->f_path.dentry;
	orig_bstart = dbstart(dentry);
	orig_bend = dbend(dentry);
	err = unionfs_partial_lookup(dentry, parent);
	if (err)
		goto out;
	bstart = dbstart(dentry);
	bend = dbend(dentry);

	FD_ZERO(&branchlist);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;
		if (likely(lower_dentry->d_inode))
			FD_SET(bindex, &branchlist);
		/* purge any lower objects after partial_lookup */
		if (bindex < orig_bstart || bindex > orig_bend) {
			dput(lower_dentry);
			unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
			iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
			unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
						    NULL);
			mnt = unionfs_lower_mnt_idx(dentry, bindex);
			if (!mnt)
				continue;
			unionfs_mntput(dentry, bindex);
			unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
		}
	}
	/* restore original dentry's offsets */
	dbstart(dentry) = orig_bstart;
	dbend(dentry) = orig_bend;
	ibstart(dentry->d_inode) = orig_bstart;
	ibend(dentry->d_inode) = orig_bend;

	err = copy_to_user((void __user *)arg, &branchlist, sizeof(fd_set));
	if (unlikely(err))
		err = -EFAULT;

out:
	return err < 0 ? err : bend;
}

int unionfs_rmdir(struct inode *dir, struct dentry *dentry)
{
	int err = 0;
	struct unionfs_dir_state *namelist = NULL;

	print_entry_location();
	lock_dentry(dentry);
	fist_print_dentry("IN unionfs_rmdir: ", dentry);

	/* check if this unionfs directory is empty or not */
	err = check_empty(dentry, &namelist);
	if (err) {
		goto out;
	}

	if (IS_SET(dir->i_sb, DELETE_WHITEOUT)) {
		/* Delete the first directory. */
		err = unionfs_rmdir_first(dir, dentry, namelist);
		/* create whiteout */
		if (!err) {
			err = create_whiteout(dentry, dbstart(dentry));
		} else {
			int new_err;

			if (dbstart(dentry) == 0)
				goto out;

			/* exit if the error returned was NOT -EROFS */
			if (!IS_COPYUP_ERR(err))
				goto out;

			new_err = create_whiteout(dentry, dbstart(dentry) - 1);
			if (new_err != -EEXIST)
				err = new_err;
		}
	} else {
		/* delete all. */
		err = unionfs_rmdir_all(dir, dentry, namelist);
	}

      out:
	/* call d_drop so the system "forgets" about us */
	if (!err)
		d_drop(dentry);

	if (namelist)
		free_rdstate(namelist);

	unlock_dentry(dentry);
	print_exit_status(err);
	return err;
}

static void unionfs_fill_inode(struct dentry *dentry,
                               struct inode *inode)
{
    struct inode *lower_inode;
    struct dentry *lower_dentry;
    int bindex, bstart, bend;

    bstart = dbstart(dentry);
    bend = dbend(dentry);

    for (bindex = bstart; bindex <= bend; bindex++) {
        lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
        if (!lower_dentry) {
            unionfs_set_lower_inode_idx(inode, bindex, NULL);
            continue;
        }

        /* Initialize the lower inode to the new lower inode. */
        if (!lower_dentry->d_inode)
            continue;

        unionfs_set_lower_inode_idx(inode, bindex,
                                    igrab(lower_dentry->d_inode));
    }

    ibstart(inode) = dbstart(dentry);
    ibend(inode) = dbend(dentry);

    /* Use attributes from the first branch. */
    lower_inode = unionfs_lower_inode(inode);

    /* Use different set of inode ops for symlinks & directories */
    if (S_ISLNK(lower_inode->i_mode))
        inode->i_op = &unionfs_symlink_iops;
    else if (S_ISDIR(lower_inode->i_mode))
        inode->i_op = &unionfs_dir_iops;

    /* Use different set of file ops for directories */
    if (S_ISDIR(lower_inode->i_mode))
        inode->i_fop = &unionfs_dir_fops;

    /* properly initialize special inodes */
    if (S_ISBLK(lower_inode->i_mode) || S_ISCHR(lower_inode->i_mode) ||
            S_ISFIFO(lower_inode->i_mode) || S_ISSOCK(lower_inode->i_mode))
        init_special_inode(inode, lower_inode->i_mode,
                           lower_inode->i_rdev);

    /* all well, copy inode attributes */
    unionfs_copy_attr_all(inode, lower_inode);
    fsstack_copy_inode_size(inode, lower_inode);
}

/* unionfs_open helper function: open a directory */
static int __open_dir(struct inode *inode, struct file *file)
{
	struct dentry *lower_dentry;
	struct file *lower_file;
	int bindex, bstart, bend;
	struct vfsmount *mnt;

	bstart = fbstart(file) = dbstart(file->f_path.dentry);
	bend = fbend(file) = dbend(file->f_path.dentry);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry =
			unionfs_lower_dentry_idx(file->f_path.dentry, bindex);
		if (!lower_dentry)
			continue;

		dget(lower_dentry);
		unionfs_mntget(file->f_path.dentry, bindex);
		mnt = unionfs_lower_mnt_idx(file->f_path.dentry, bindex);
		lower_file = dentry_open(lower_dentry, mnt, file->f_flags,
					 current_cred());
		if (IS_ERR(lower_file))
			return PTR_ERR(lower_file);

		unionfs_set_lower_file_idx(file, bindex, lower_file);

		/*
		 * The branchget goes after the open, because otherwise
		 * we would miss the reference on release.
		 */
		branchget(inode->i_sb, bindex);
	}

	return 0;
}

/* open all lower files for a given file */
static int open_all_files(struct file *file)
{
	int bindex, bstart, bend, err = 0;
	struct file *lower_file;
	struct dentry *lower_dentry;
	struct dentry *dentry = file->f_path.dentry;
	struct super_block *sb = dentry->d_sb;

	bstart = dbstart(dentry);
	bend = dbend(dentry);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;

		dget(lower_dentry);
		unionfs_mntget(dentry, bindex);
		branchget(sb, bindex);

		lower_file =
			dentry_open(lower_dentry,
				    unionfs_lower_mnt_idx(dentry, bindex),
				    file->f_flags, current_cred());
		if (IS_ERR(lower_file)) {
			branchput(sb, bindex);
			err = PTR_ERR(lower_file);
			goto out;
		} else {
			unionfs_set_lower_file_idx(file, bindex, lower_file);
		}
	}
out:
	return err;
}

/*
 * scan through the lower dentry objects, and set bstart to reflect the
 * starting branch
 */
void update_bstart(struct dentry *dentry)
{
	int bindex;
	int bstart = dbstart(dentry);
	int bend = dbend(dentry);
	struct dentry *lower_dentry;

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;
		if (lower_dentry->d_inode) {
			dbstart(dentry) = bindex;
			break;
		}
		dput(lower_dentry);
		unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
	}
}

/*
 * dput the lower references for old and new dentry & clear a lower dentry
 * pointer
 */
static void __clear(struct dentry *dentry, struct dentry *old_lower_dentry,
		    int old_bstart, int old_bend,
		    struct dentry *new_lower_dentry, int new_bindex)
{
	/* get rid of the lower dentry and all its traces */
	unionfs_set_lower_dentry_idx(dentry, new_bindex, NULL);
	dbstart(dentry) = old_bstart;
	dbend(dentry) = old_bend;

	dput(new_lower_dentry);
	dput(old_lower_dentry);
}

static void epilog(struct inode *dir, struct dentry *dentry,
		   aufs_bindex_t bindex)
{
	d_drop(dentry);
	dentry->d_inode->i_ctime = dir->i_ctime;
	if (atomic_read(&dentry->d_count) == 1) {
		set_h_dptr(dentry, dbstart(dentry), NULL);
		au_update_dbstart(dentry);
	}
	if (ibstart(dir) == bindex)
		au_cpup_attr_timesizes(dir);
	dir->i_version++;
}

/*
 * Post-copyup helper to release all non-directory source objects of a
 * copied-up file.  Regular files should have only one lower object.
 */
void unionfs_postcopyup_release(struct dentry *dentry)
{
	int bstart, bend;

	BUG_ON(S_ISDIR(dentry->d_inode->i_mode));
	bstart = dbstart(dentry);
	bend = dbend(dentry);

	path_put_lowers(dentry, bstart + 1, bend, false);
	iput_lowers(dentry->d_inode, bstart + 1, bend, false);

	dbend(dentry) = bstart;
	ibend(dentry->d_inode) = ibstart(dentry->d_inode) = bstart;
}

/*
 * We can't copyup a directory, because it may involve huge numbers of
 * children, etc.  Doing that in the kernel would be bad, so instead we
 * return EXDEV to the user-space utility that caused this, and let the
 * user-space recurse and ask us to copy up each file separately.
 */
static int may_rename_dir(struct dentry *dentry, struct dentry *parent)
{
	int err, bstart;

	err = check_empty(dentry, parent, NULL);
	if (err == -ENOTEMPTY) {
		if (is_robranch(dentry))
			return -EXDEV;
	} else if (err) {
		return err;
	}

	bstart = dbstart(dentry);
	if (dbend(dentry) == bstart || dbopaque(dentry) == bstart)
		return 0;

	dbstart(dentry) = bstart + 1;
	err = check_empty(dentry, parent, NULL);
	dbstart(dentry) = bstart;
	if (err == -ENOTEMPTY)
		err = -EXDEV;
	return err;
}

/*
 * unionfs_lookup is the only special function which takes a dentry, yet we
 * do NOT want to call __unionfs_d_revalidate_chain because by definition,
 * we don't have a valid dentry here yet.
 */
static struct dentry *unionfs_lookup(struct inode *dir,
				     struct dentry *dentry,
				     /* XXX: pass flags to lower? */
				     unsigned int flags_unused)
{
	struct dentry *ret, *parent;
	int err = 0;

	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
	parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);

	/*
	 * As long as we lock/dget the parent, then can skip validating the
	 * parent now; we may have to rebuild this dentry on the next
	 * ->d_revalidate, however.
	 */

	/* allocate dentry private data.  We free it in ->d_release */
	err = new_dentry_private_data(dentry, UNIONFS_DMUTEX_CHILD);
	if (unlikely(err)) {
		ret = ERR_PTR(err);
		goto out;
	}

	ret = unionfs_lookup_full(dentry, parent, INTERPOSE_LOOKUP);

	if (!IS_ERR(ret)) {
		if (ret)
			dentry = ret;
		/* lookup_full can return multiple positive dentries */
		if (dentry->d_inode && !S_ISDIR(dentry->d_inode->i_mode)) {
			BUG_ON(dbstart(dentry) < 0);
			unionfs_postcopyup_release(dentry);
		}
		unionfs_copy_attr_times(dentry->d_inode);
	}

	unionfs_check_inode(dir);
	if (!IS_ERR(ret))
		unionfs_check_dentry(dentry);
	unionfs_check_dentry(parent);
	unionfs_unlock_dentry(dentry); /* locked in new_dentry_private data */

out:
	unionfs_unlock_parent(dentry, parent);
	unionfs_read_unlock(dentry->d_sb);

	return ret;
}

/* perform a delayed copyup of a read-write file on a read-only branch */
static int do_delayed_copyup(struct file *file, struct dentry *parent)
{
	int bindex, bstart, bend, err = 0;
	struct dentry *dentry = file->f_path.dentry;
	struct inode *parent_inode = parent->d_inode;

	bstart = fbstart(file);
	bend = fbend(file);

	BUG_ON(!S_ISREG(dentry->d_inode->i_mode));

	unionfs_check_file(file);
	for (bindex = bstart - 1; bindex >= 0; bindex--) {
		if (!d_deleted(dentry))
			err = copyup_file(parent_inode, file, bstart,
					  bindex,
					  i_size_read(dentry->d_inode));
		else
			err = copyup_deleted_file(file, dentry, parent,
						  bstart, bindex);
		/* if succeeded, set lower open-file flags and break */
		if (!err) {
			struct file *lower_file;
			lower_file = unionfs_lower_file_idx(file, bindex);
			lower_file->f_flags = file->f_flags;
			break;
		}
	}
	if (err || (bstart <= fbstart(file)))
		goto out;
	bend = fbend(file);
	for (bindex = bstart; bindex <= bend; bindex++) {
		if (unionfs_lower_file_idx(file, bindex)) {
			branchput(dentry->d_sb, bindex);
			fput(unionfs_lower_file_idx(file, bindex));
			unionfs_set_lower_file_idx(file, bindex, NULL);
		}
	}
	path_put_lowers(dentry, bstart, bend, false);
	iput_lowers(dentry->d_inode, bstart, bend, false);
	/* for reg file, we only open it "once" */
	fbend(file) = fbstart(file);
	dbend(dentry) = dbstart(dentry);
	ibend(dentry->d_inode) = ibstart(dentry->d_inode);

out:
	unionfs_check_file(file);
	return err;
}

/* purge a dentry's lower-branch states (dput/mntput, etc.) */
static void __cleanup_dentry(struct dentry *dentry, int bindex,
			     int old_bstart, int old_bend)
{
	int loop_start;
	int loop_end;
	int new_bstart = -1;
	int new_bend = -1;
	int i;

	loop_start = min(old_bstart, bindex);
	loop_end = max(old_bend, bindex);

	/*
	 * This loop sets the bstart and bend for the new dentry by
	 * traversing from left to right.  It also dputs all negative
	 * dentries except bindex
	 */
	for (i = loop_start; i <= loop_end; i++) {
		if (!unionfs_lower_dentry_idx(dentry, i))
			continue;

		if (i == bindex) {
			new_bend = i;
			if (new_bstart < 0)
				new_bstart = i;
			continue;
		}

		if (!unionfs_lower_dentry_idx(dentry, i)->d_inode) {
			dput(unionfs_lower_dentry_idx(dentry, i));
			unionfs_set_lower_dentry_idx(dentry, i, NULL);

			unionfs_mntput(dentry, i);
			unionfs_set_lower_mnt_idx(dentry, i, NULL);
		} else {
			if (new_bstart < 0)
				new_bstart = i;
			new_bend = i;
		}
	}

	if (new_bstart < 0)
		new_bstart = bindex;
	if (new_bend < 0)
		new_bend = bindex;
	dbstart(dentry) = new_bstart;
	dbend(dentry) = new_bend;

}