C++ dget函数代码示例

//.........这里部分代码省略.........
	struct dentry *h_src_dentry;
	struct mutex *h_mtx;
	struct file *h_file;

	di_read_lock_parent(a->src_parent, AuLock_IR);
	err = au_test_and_cpup_dirs(src_dentry, a->bdst);
	if (unlikely(err))
		goto out;

	h_src_dentry = au_h_dptr(src_dentry, a->bsrc);
	h_mtx = &h_src_dentry->d_inode->i_mutex;
	err = au_pin(&a->pin, src_dentry, a->bdst,
		     au_opt_udba(src_dentry->d_sb),
		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
	if (unlikely(err))
		goto out;
	mutex_lock_nested(h_mtx, AuLsc_I_CHILD);
	h_file = au_h_open_pre(src_dentry, a->bsrc);
	if (IS_ERR(h_file)) {
		err = PTR_ERR(h_file);
		h_file = NULL;
	} else
		err = au_sio_cpup_simple(src_dentry, a->bdst, a->bsrc,
					 AuCpup_DTIME /* | AuCpup_KEEPLINO */);
	mutex_unlock(h_mtx);
	au_h_open_post(src_dentry, a->bsrc, h_file);
	au_unpin(&a->pin);

out:
	di_read_unlock(a->src_parent, AuLock_IR);
	return err;
}

static int au_cpup_or_link(struct dentry *src_dentry, struct au_link_args *a)
{
	int err;
	unsigned char plink;
	struct inode *h_inode, *inode;
	struct dentry *h_src_dentry;
	struct super_block *sb;
	struct file *h_file;

	plink = 0;
	h_inode = NULL;
	sb = src_dentry->d_sb;
	inode = src_dentry->d_inode;
	if (au_ibstart(inode) <= a->bdst)
		h_inode = au_h_iptr(inode, a->bdst);
	if (!h_inode || !h_inode->i_nlink) {
		/* copyup src_dentry as the name of dentry. */
		au_set_dbstart(src_dentry, a->bdst);
		au_set_h_dptr(src_dentry, a->bdst, dget(a->h_path.dentry));
		h_inode = au_h_dptr(src_dentry, a->bsrc)->d_inode;
		mutex_lock_nested(&h_inode->i_mutex, AuLsc_I_CHILD);
		h_file = au_h_open_pre(src_dentry, a->bsrc);
		if (IS_ERR(h_file)) {
			err = PTR_ERR(h_file);
			h_file = NULL;
		} else
			err = au_sio_cpup_single(src_dentry, a->bdst, a->bsrc,
						 -1, AuCpup_KEEPLINO,
						 a->parent);
		mutex_unlock(&h_inode->i_mutex);
		au_h_open_post(src_dentry, a->bsrc, h_file);
		au_set_h_dptr(src_dentry, a->bdst, NULL);
		au_set_dbstart(src_dentry, a->bsrc);
	} else {
		/* the inode of src_dentry already exists on a.bdst branch */
		h_src_dentry = d_find_alias(h_inode);
		if (!h_src_dentry && au_plink_test(inode)) {
			plink = 1;
			h_src_dentry = au_plink_lkup(inode, a->bdst);
			err = PTR_ERR(h_src_dentry);
			if (IS_ERR(h_src_dentry))
				goto out;

			if (unlikely(!h_src_dentry->d_inode)) {
				dput(h_src_dentry);
				h_src_dentry = NULL;
			}

		}
		if (h_src_dentry) {
			err = vfsub_link(h_src_dentry, au_pinned_h_dir(&a->pin),
					 &a->h_path);
			dput(h_src_dentry);
		} else {
			AuIOErr("no dentry found for hi%lu on b%d\n",
				h_inode->i_ino, a->bdst);
			err = -EIO;
		}
	}

	if (!err && !plink)
		au_plink_append(inode, a->bdst, a->h_path.dentry);

out:
	AuTraceErr(err);
	return err;
}

__be32
nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
		   const char *name, unsigned int len,
		   struct svc_export **exp_ret, struct dentry **dentry_ret)
{
	struct svc_export	*exp;
	struct dentry		*dparent;
	struct dentry		*dentry;
	__be32			err;
	int			host_err;

	dprintk("nfsd: nfsd_lookup(fh %s, %.*s)\n", SVCFH_fmt(fhp), len,name);

	/* Obtain dentry and export. */
	err = fh_verify(rqstp, fhp, S_IFDIR, MAY_EXEC);
	if (err)
		return err;

	dparent = fhp->fh_dentry;
	exp  = fhp->fh_export;
	exp_get(exp);

	/* Lookup the name, but don't follow links */
	if (isdotent(name, len)) {
		if (len==1)
			dentry = dget(dparent);
		else if (dparent != exp->ex_path.dentry)
			dentry = dget_parent(dparent);
		else if (!EX_NOHIDE(exp))
			dentry = dget(dparent); /* .. == . just like at / */
		else {
			/* checking mountpoint crossing is very different when stepping up */
			struct svc_export *exp2 = NULL;
			struct dentry *dp;
			struct vfsmount *mnt = mntget(exp->ex_path.mnt);
			dentry = dget(dparent);
			while(dentry == mnt->mnt_root && follow_up(&mnt, &dentry))
				;
			dp = dget_parent(dentry);
			dput(dentry);
			dentry = dp;

			exp2 = rqst_exp_parent(rqstp, mnt, dentry);
			if (PTR_ERR(exp2) == -ENOENT) {
				dput(dentry);
				dentry = dget(dparent);
			} else if (IS_ERR(exp2)) {
				host_err = PTR_ERR(exp2);
				dput(dentry);
				mntput(mnt);
				goto out_nfserr;
			} else {
				exp_put(exp);
				exp = exp2;
			}
			mntput(mnt);
		}
	} else {
		fh_lock(fhp);
		dentry = lookup_one_len(name, dparent, len);
		host_err = PTR_ERR(dentry);
		if (IS_ERR(dentry))
			goto out_nfserr;
		/*
		 * check if we have crossed a mount point ...
		 */
		if (d_mountpoint(dentry)) {
			if ((host_err = nfsd_cross_mnt(rqstp, &dentry, &exp))) {
				dput(dentry);
				goto out_nfserr;
			}
		}
	}
	*dentry_ret = dentry;
	*exp_ret = exp;
	return 0;

out_nfserr:
	exp_put(exp);
	return nfserrno(host_err);
}

/**
 * securityfs_create_file - create a file in the securityfs filesystem
 *
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the securityfs filesystem.
 * @data: a pointer to something that the caller will want to get to later
 *        on.  The inode.i_private pointer will point to this value on
 *        the open() call.
 * @fops: a pointer to a struct file_operations that should be used for
 *        this file.
 *
 * This is the basic "create a file" function for securityfs.  It allows for a
 * wide range of flexibility in creating a file, or a directory (if you
 * want to create a directory, the securityfs_create_dir() function is
 * recommended to be used instead).
 *
 * This function returns a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the securityfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here).  If an error occurs, the function will return
 * the error value (via ERR_PTR).
 *
 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 * returned.
 */
struct dentry *securityfs_create_file(const char *name, umode_t mode,
				   struct dentry *parent, void *data,
				   const struct file_operations *fops)
{
	struct dentry *dentry;
	int is_dir = S_ISDIR(mode);
	struct inode *dir, *inode;
	int error;

	if (!is_dir) {
		BUG_ON(!fops);
		mode = (mode & S_IALLUGO) | S_IFREG;
	}

	pr_debug("securityfs: creating file '%s'\n",name);

	error = simple_pin_fs(&fs_type, &mount, &mount_count);
	if (error)
		return ERR_PTR(error);

	if (!parent)
		parent = mount->mnt_root;

	dir = d_inode(parent);

	inode_lock(dir);
	dentry = lookup_one_len(name, parent, strlen(name));
	if (IS_ERR(dentry))
		goto out;

	if (d_really_is_positive(dentry)) {
		error = -EEXIST;
		goto out1;
	}

	inode = new_inode(dir->i_sb);
	if (!inode) {
		error = -ENOMEM;
		goto out1;
	}

	inode->i_ino = get_next_ino();
	inode->i_mode = mode;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_private = data;
	if (is_dir) {
		inode->i_op = &simple_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;
		inc_nlink(inode);
		inc_nlink(dir);
	} else {
		inode->i_fop = fops;
	}
	d_instantiate(dentry, inode);
	dget(dentry);
	inode_unlock(dir);
	return dentry;

out1:
	dput(dentry);
	dentry = ERR_PTR(error);
out:
	inode_unlock(dir);
	simple_release_fs(&mount, &mount_count);
	return dentry;
}

/* cr_mknod - based on linux/fs/namei.c:sys_mknod
 *
 * Creates regular files or fifos (no devices) making them anonymous (unlinked)
 * if desired.
 * Returns a dentry for the resulting filesystem objects, and the corresponding
 * vfsmnt can be obtained in nd->mnt.  Together these two can be passed
 * to dentry_open() or cr_dentry_open(), even for an unlinked inode.
 * In the event of an error, no dput() or cr_path_release() is required,
 * otherwise they are.
 *
 * In the event that an object exists with the given name, it will be
 * check for the proper mode prior to return, yielding -EEXIST on conflict.
 */
struct dentry *
cr_mknod(cr_errbuf_t *eb, struct nameidata *nd, const char *name, int mode, unsigned long unlinked_id)
{
    struct dentry * dentry;
    int err;

    if (unlinked_id) {
	/* Generate a replacement name which we will use instead of the original one. */
	name = cr_anonymous_rename(eb, name, unlinked_id);
	if (!name) {
	    CR_ERR_EB(eb, "cr_mknod - failed to rename unlinked object");
	    err = -ENOMEM;
	    goto out;
	}
    }

    /* Prior to 2.6.26, lookup_create() would return an exisiting dentry.
     * Since 2.6.26, it returns -EEXIST if the dentry exists.  So, we first
     * check for an existing dentry.  For older kernels this is not required,
     * but is still correct.
     */
    err = path_lookup(name, LOOKUP_FOLLOW, nd);
    if (!err) {
	dentry = dget(nd->nd_dentry);
	err = -EEXIST; /* Forces mode validation below */
	goto have_it;
    }

    err = path_lookup(name, LOOKUP_PARENT, nd);
    if (err) {
	CR_KTRACE_UNEXPECTED("Couldn't path_lookup for mknod %s.  err=%d.", name, err);
	goto out_free;
    }

    dentry = cr_lookup_create(nd, 0);
    if (IS_ERR(dentry)) {
	err = PTR_ERR(dentry);
	CR_KTRACE_UNEXPECTED("Couldn't lookup_create for mknod %s.  err=%d.", name, err);
	goto out_release;
    }

    switch (mode & S_IFMT) {
    case S_IFREG:
	err = vfs_create(nd->nd_dentry->d_inode, dentry, mode, nd);
	break;
    case S_IFIFO:
	err = cr_vfs_mknod(nd->nd_dentry->d_inode, dentry, nd->nd_mnt, mode, 0 /* ignored */);
	break;
    default:
	CR_ERR_EB(eb, "Unknown/invalid type %d passed to cr_mknod %s.", (mode&S_IFMT), name);
	err = -EINVAL;
    }
    if (unlinked_id && !err) { /* Note that we don't unlink if we failed to create */
	dget(dentry);	/* ensure unlink doesn't destroy the dentry */
	/* Note possibility of silent failure here: */
	(void)cr_vfs_unlink(nd->nd_dentry->d_inode, dentry, nd->nd_mnt);
	dput(dentry);
    }
    cr_inode_unlock(nd->nd_dentry->d_inode);

have_it:
    if ((err == -EEXIST) && !((dentry->d_inode->i_mode ^ mode) & S_IFMT)) {
	/* We fall through and return the dentry */
    } else if (err) {
	CR_KTRACE_UNEXPECTED("Couldn't cr_mknod %s.  err=%d.", name, err);
	goto out_put;
    }

    if (unlinked_id) {
	__putname(name);
    }
    return dentry;

out_put:
    dput(dentry);
out_release:
    cr_path_release(nd);
out_free:
    if (unlinked_id) {
	__putname(name);
    }
out:
    return (struct dentry *)ERR_PTR(err);
}

/*
 * Do a lookup + open with a single request.  If we get a non-existent
 * file or symlink, return 1 so the VFS can retry.
 */
int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
		     struct file *file, unsigned flags, umode_t mode,
		     int *opened)
{
	struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
	struct ceph_mds_client *mdsc = fsc->mdsc;
	struct ceph_mds_request *req;
	struct dentry *dn;
	int err;

	dout("atomic_open %p dentry %p '%.*s' %s flags %d mode 0%o\n",
	     dir, dentry, dentry->d_name.len, dentry->d_name.name,
	     d_unhashed(dentry) ? "unhashed" : "hashed", flags, mode);

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

	err = ceph_init_dentry(dentry);
	if (err < 0)
		return err;

	/* do the open */
	req = prepare_open_request(dir->i_sb, flags, mode);
	if (IS_ERR(req))
		return PTR_ERR(req);
	req->r_dentry = dget(dentry);
	req->r_num_caps = 2;
	if (flags & O_CREAT) {
		req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
		req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
	}
	req->r_locked_dir = dir;           /* caller holds dir->i_mutex */
	err = ceph_mdsc_do_request(mdsc,
				   (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
				   req);
	if (err)
		goto out_err;

	err = ceph_handle_snapdir(req, dentry, err);
	if (err == 0 && (flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
		err = ceph_handle_notrace_create(dir, dentry);

	if (d_unhashed(dentry)) {
		dn = ceph_finish_lookup(req, dentry, err);
		if (IS_ERR(dn))
			err = PTR_ERR(dn);
	} else {
		/* we were given a hashed negative dentry */
		dn = NULL;
	}
	if (err)
		goto out_err;
	if (dn || dentry->d_inode == NULL || S_ISLNK(dentry->d_inode->i_mode)) {
		/* make vfs retry on splice, ENOENT, or symlink */
		dout("atomic_open finish_no_open on dn %p\n", dn);
		err = finish_no_open(file, dn);
	} else {
		dout("atomic_open finish_open on dn %p\n", dn);
		if (req->r_op == CEPH_MDS_OP_CREATE && req->r_reply_info.has_create_ino) {
			*opened |= FILE_CREATED;
		}
		err = finish_open(file, dentry, ceph_open, opened);
	}

out_err:
	ceph_mdsc_put_request(req);
	dout("atomic_open result=%d\n", err);
	return err;
}

/* The inode's security attributes must be initialized before first use. */
static int inode_doinit_with_dentry(struct inode *inode,
				struct dentry *opt_dentry)
{
	struct inode_security_struct *isec = inode->i_security;
	struct dentry *dentry;
	char *context = NULL;
	unsigned len = 0;
	int rc = 0;

	if (isec && isec->initialized)
		return rc;

	mutex_lock(&isec->lock);
	if (!inode->i_op->getxattr) {
		/* no getxattr iop, so init */
		pr_debug("no xattr iop when init\n");
		isec->task_sid = current_uid();
		init_mlevel(&isec->mlevel);
		isec->ilevel.level_value = 0;
		goto out;
	}

	/* Need a dentry, since the xattr API requires one.
	   Life would be simpler if we could just pass the inode. */
	if (opt_dentry)
		/* Called from d_instantiate or d_splice_alias. */
		dentry = dget(opt_dentry);
	if (!dentry) {
		/*
		 * this is can be hit on boot when a file is accessed
		 * inode_doinit with a dentry, before these inodes could
		 * be used again by userspace.
		 */
		goto out;
	}

	/* Query for the right size. */
	rc = inode->i_op->getxattr(dentry, XATTR_NAME_KSE,
				   NULL, 0);
	if (rc < 0) {
		dput(dentry);
		goto out;
	}

	len = rc;
	context = kmalloc(len+1, GFP_NOFS);
	if (!context) {
		rc = -ENOMEM;
		dput(dentry);
		goto out;
	}
	context[len] = '\0';
	rc = inode->i_op->getxattr(dentry, XATTR_NAME_KSE,
				   context, len);
	if (rc == -ERANGE) {
		kfree(context);

		/* Need a larger buffer.  Query for the right size. */
		rc = inode->i_op->getxattr(dentry, XATTR_NAME_KSE,
					   NULL, 0);
		if (rc < 0) {
			dput(dentry);
			goto out;
		}
		len = rc;
		context = kmalloc(len+1, GFP_NOFS);
		if (!context) {
			rc = -ENOMEM;
			dput(dentry);
			goto out;
		}
		context[len] = '\0';
		rc = inode->i_op->getxattr(dentry,
					   XATTR_NAME_KSE,
					   context, len);
	}
	dput(dentry);
	if (rc < 0) {
		if (rc != -ENODATA) {
			printk(KERN_INFO "KUXSE: %s:  getxattr returned "
				"%d for dev=%s ino=%ld\n", __func__,
				-rc, inode->i_sb->s_id, inode->i_ino);
			kfree(context);
			goto out;
		}
		/* NODATA just init */
		rc = 0; 
		pr_debug("no xattr data when init\n");
		isec->task_sid = current_uid();
		init_mlevel(&isec->mlevel);
		isec->ilevel.level_value = 0;
	} else {
		/* getxattr succeeded */
		ssize_t sclen = strlen(context);
		rc = context_to_iss(&isec->mlevel, &isec->ilevel,
				(const void **)&context, &sclen);
		if (rc) {
			printk(KERN_INFO "KUXSE:  unable to map value '%s' "
				"to context for (%s, %lu), rc=%d, size=%ld\n",
//.........这里部分代码省略.........

/*
 * Find an eligible tree to time-out
 * A tree is eligible if :-
 *  - it is unused by any user process
 *  - it has been unused for exp_timeout time
 */
static struct dentry *autofs4_expire_indirect(struct super_block *sb,
					      struct vfsmount *mnt,
					      struct autofs_sb_info *sbi,
					      int how)
{
	unsigned long timeout;
	struct dentry *root = sb->s_root;
	struct dentry *expired = NULL;
	struct list_head *next;
	int do_now = how & AUTOFS_EXP_IMMEDIATE;
	int exp_leaves = how & AUTOFS_EXP_LEAVES;

	if (!root)
		return NULL;

	now = jiffies;
	timeout = sbi->exp_timeout;

	spin_lock(&dcache_lock);
	next = root->d_subdirs.next;

	/* On exit from the loop expire is set to a dgot dentry
	 * to expire or it's NULL */
	while ( next != &root->d_subdirs ) {
		struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);

		/* Negative dentry - give up */
		if (!simple_positive(dentry)) {
			next = next->next;
			continue;
		}

		dentry = dget(dentry);
		spin_unlock(&dcache_lock);

		/*
		 * Case 1: (i) indirect mount or top level pseudo direct mount
		 *	   (autofs-4.1).
		 *	   (ii) indirect mount with offset mount, check the "/"
		 *	   offset (autofs-5.0+).
		 */
		if (d_mountpoint(dentry)) {
			DPRINTK("checking mountpoint %p %.*s",
				dentry, (int)dentry->d_name.len, dentry->d_name.name);

			/* Can we umount this guy */
			if (autofs4_mount_busy(mnt, dentry))
				goto next;

			/* Can we expire this guy */
			if (autofs4_can_expire(dentry, timeout, do_now)) {
				expired = dentry;
				break;
			}
			goto next;
		}

		if (simple_empty(dentry))
			goto next;

		/* Case 2: tree mount, expire iff entire tree is not busy */
		if (!exp_leaves) {
			/* Lock the tree as we must expire as a whole */
			spin_lock(&sbi->fs_lock);
			if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
				struct autofs_info *inf = autofs4_dentry_ino(dentry);

				/* Set this flag early to catch sys_chdir and the like */
				inf->flags |= AUTOFS_INF_EXPIRING;
				spin_unlock(&sbi->fs_lock);
				expired = dentry;
				break;
			}
			spin_unlock(&sbi->fs_lock);
		/*
		 * Case 3: pseudo direct mount, expire individual leaves
		 *	   (autofs-4.1).
		 */
		} else {
			expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
			if (expired) {
				dput(dentry);
				break;
			}
		}
next:
		dput(dentry);
		spin_lock(&dcache_lock);
		next = next->next;
	}

	if (expired) {
		DPRINTK("returning %p %.*s",
			expired, (int)expired->d_name.len, expired->d_name.name);
//.........这里部分代码省略.........

int ovl_permission(struct inode *inode, int mask)
{
	struct ovl_entry *oe;
	struct dentry *alias = NULL;
	struct inode *realinode;
	struct dentry *realdentry;
	bool is_upper;
	int err;

	if (S_ISDIR(inode->i_mode)) {
		oe = inode->i_private;
	} else if (mask & MAY_NOT_BLOCK) {
		return -ECHILD;
	} else {
		/*
		 * For non-directories find an alias and get the info
		 * from there.
		 */
		spin_lock(&inode->i_lock);
		if (WARN_ON(list_empty(&inode->i_dentry))) {
			spin_unlock(&inode->i_lock);
			return -ENOENT;
		}
		alias = list_entry(inode->i_dentry.next,
				   struct dentry, d_u.d_alias);
		dget(alias);
		spin_unlock(&inode->i_lock);
		oe = alias->d_fsdata;
	}

	realdentry = ovl_entry_real(oe, &is_upper);

	/* Careful in RCU walk mode */
	realinode = ACCESS_ONCE(realdentry->d_inode);
	if (!realinode) {
		WARN_ON(!(mask & MAY_NOT_BLOCK));
		err = -ENOENT;
		goto out_dput;
	}

	if (mask & MAY_WRITE) {
		umode_t mode = realinode->i_mode;

		/*
		 * Writes will always be redirected to upper layer, so
		 * ignore lower layer being read-only.
		 *
		 * If the overlay itself is read-only then proceed
		 * with the permission check, don't return EROFS.
		 * This will only happen if this is the lower layer of
		 * another overlayfs.
		 *
		 * If upper fs becomes read-only after the overlay was
		 * constructed return EROFS to prevent modification of
		 * upper layer.
		 */
		err = -EROFS;
		if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
			goto out_dput;
	}

	err = inode_only_permission(realinode, mask);
out_dput:
	dput(alias);
	return err;
}

static inline void copy_namei(struct nameidata *dest, const struct nameidata *src) {
	mntget(src->mnt);  dget(src->dentry);
	*dest = *src;
}

/* Check a directory tree of mount points for busyness
 * The tree is not busy iff no mountpoints are busy
 */
static int autofs4_tree_busy(struct vfsmount *mnt,
	       		     struct dentry *top,
			     unsigned long timeout,
			     int do_now)
{
	struct autofs_info *top_ino = autofs4_dentry_ino(top);
	struct dentry *p;

	DPRINTK("top %p %.*s",
		top, (int)top->d_name.len, top->d_name.name);

	/* Negative dentry - give up */
	if (!simple_positive(top))
		return 1;

	spin_lock(&dcache_lock);
	for (p = top; p; p = next_dentry(p, top)) {
		/* Negative dentry - give up */
		if (!simple_positive(p))
			continue;

		DPRINTK("dentry %p %.*s",
			p, (int) p->d_name.len, p->d_name.name);

		p = dget(p);
		spin_unlock(&dcache_lock);

		/*
		 * Is someone visiting anywhere in the subtree ?
		 * If there's no mount we need to check the usage
		 * count for the autofs dentry.
		 * If the fs is busy update the expiry counter.
		 */
		if (d_mountpoint(p)) {
			if (autofs4_mount_busy(mnt, p)) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		} else {
			struct autofs_info *ino = autofs4_dentry_ino(p);
			unsigned int ino_count = atomic_read(&ino->count);

			/*
			 * Clean stale dentries below that have not been
			 * invalidated after a mount fail during lookup
			 */
			d_invalidate(p);

			/* allow for dget above and top is already dgot */
			if (p == top)
				ino_count += 2;
			else
				ino_count++;

			if (atomic_read(&p->d_count) > ino_count) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		}
		dput(p);
		spin_lock(&dcache_lock);
	}
	spin_unlock(&dcache_lock);

	/* Timeout of a tree mount is ultimately determined by its top dentry */
	if (!autofs4_can_expire(top, timeout, do_now))
		return 1;

	return 0;
}

void redirect_namei(struct nameidata *dest, const struct nameidata *src) {
	mntget(src->mnt);  dget(src->dentry);
	mntput(dest->mnt); dput(dest->dentry);
	*dest = *src;
}

/* Is a directory logically empty? */
int check_empty(struct dentry *dentry, struct dentry *parent,
		struct unionfs_dir_state **namelist)
{
	int err = 0;
	struct dentry *lower_dentry = NULL;
	struct vfsmount *mnt;
	struct super_block *sb;
	struct file *lower_file;
	struct unionfs_rdutil_callback *buf = NULL;
	int bindex, bstart, bend, bopaque;

	sb = dentry->d_sb;


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

	err = unionfs_partial_lookup(dentry, parent);
	if (err)
		goto out;

	bstart = dbstart(dentry);
	bend = dbend(dentry);
	bopaque = dbopaque(dentry);
	if (0 <= bopaque && bopaque < bend)
		bend = bopaque;

	buf = kmalloc(sizeof(struct unionfs_rdutil_callback), GFP_KERNEL);
	if (unlikely(!buf)) {
		err = -ENOMEM;
		goto out;
	}
	buf->err = 0;
	buf->mode = RD_CHECK_EMPTY;
	buf->rdstate = alloc_rdstate(dentry->d_inode, bstart);
	if (unlikely(!buf->rdstate)) {
		err = -ENOMEM;
		goto out;
	}

	/* Process the lower directories with rdutil_callback as a filldir. */
	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 (!S_ISDIR(lower_dentry->d_inode->i_mode))
			continue;

		dget(lower_dentry);
		mnt = unionfs_mntget(dentry, bindex);
		branchget(sb, bindex);
		lower_file = dentry_open(lower_dentry, mnt, O_RDONLY);
		if (IS_ERR(lower_file)) {
			err = PTR_ERR(lower_file);
			branchput(sb, bindex);
			goto out;
		}

		do {
			buf->filldir_called = 0;
			buf->rdstate->bindex = bindex;
			err = vfs_readdir(lower_file,
					  readdir_util_callback, buf);
			if (buf->err)
				err = buf->err;
		} while ((err >= 0) && buf->filldir_called);

		/* fput calls dput for lower_dentry */
		fput(lower_file);
		branchput(sb, bindex);

		if (err < 0)
			goto out;
	}

out:
	if (buf) {
		if (namelist && !err)
			*namelist = buf->rdstate;
		else if (buf->rdstate)
			free_rdstate(buf->rdstate);
		kfree(buf);
	}


	return err;
}

/*
 * By adding a dirty branch, a cached dentry may be affected in various ways.
 *
 * a dirty branch is added
 * - on the top of layers
 * - in the middle of layers
 * - to the bottom of layers
 *
 * on the added branch there exists
 * - a whiteout
 * - a diropq
 * - a same named entry
 *   + exist
 *     * negative --> positive
 *     * positive --> positive
 *	 - type is unchanged
 *	 - type is changed
 *   + doesn't exist
 *     * negative --> negative
 *     * positive --> negative (rejected by au_br_del() for non-dir case)
 * - none
 */
static int au_refresh_by_dinfo(struct dentry *dentry, struct au_dinfo *dinfo,
			       struct au_dinfo *tmp)
{
	int err;
	aufs_bindex_t bindex, bend;
	struct {
		struct dentry *dentry;
		struct inode *inode;
		mode_t mode;
	} orig_h, tmp_h;
	struct au_hdentry *hd;
	struct inode *inode, *h_inode;
	struct dentry *h_dentry;

	err = 0;
	AuDebugOn(dinfo->di_bstart < 0);
	orig_h.dentry = dinfo->di_hdentry[dinfo->di_bstart].hd_dentry;
	orig_h.inode = orig_h.dentry->d_inode;
	orig_h.mode = 0;
	if (orig_h.inode)
		orig_h.mode = orig_h.inode->i_mode & S_IFMT;
	memset(&tmp_h, 0, sizeof(tmp_h));
	if (tmp->di_bstart >= 0) {
		tmp_h.dentry = tmp->di_hdentry[tmp->di_bstart].hd_dentry;
		tmp_h.inode = tmp_h.dentry->d_inode;
		if (tmp_h.inode)
			tmp_h.mode = tmp_h.inode->i_mode & S_IFMT;
	}

	inode = dentry->d_inode;
	if (!orig_h.inode) {
		AuDbg("nagative originally\n");
		if (inode) {
			au_hide(dentry);
			goto out;
		}
		AuDebugOn(inode);
		AuDebugOn(dinfo->di_bstart != dinfo->di_bend);
		AuDebugOn(dinfo->di_bdiropq != -1);

		if (!tmp_h.inode) {
			AuDbg("negative --> negative\n");
			/* should have only one negative lower */
			if (tmp->di_bstart >= 0
			    && tmp->di_bstart < dinfo->di_bstart) {
				AuDebugOn(tmp->di_bstart != tmp->di_bend);
				AuDebugOn(dinfo->di_bstart != dinfo->di_bend);
				au_set_h_dptr(dentry, dinfo->di_bstart, NULL);
				au_di_cp(dinfo, tmp);
				hd = tmp->di_hdentry + tmp->di_bstart;
				au_set_h_dptr(dentry, tmp->di_bstart,
					      dget(hd->hd_dentry));
			}
			au_dbg_verify_dinode(dentry);
		} else {
			AuDbg("negative --> positive\n");
			/*
			 * similar to the behaviour of creating with bypassing
			 * aufs.
			 * unhash it in order to force an error in the
			 * succeeding create operation.
			 * we should not set S_DEAD here.
			 */
			d_drop(dentry);
			/* au_di_swap(tmp, dinfo); */
			au_dbg_verify_dinode(dentry);
		}
	} else {
		AuDbg("positive originally\n");
		/* inode may be NULL */
		AuDebugOn(inode && (inode->i_mode & S_IFMT) != orig_h.mode);
		if (!tmp_h.inode) {
			AuDbg("positive --> negative\n");
			/* or bypassing aufs */
			au_hide(dentry);
			if (tmp->di_bwh >= 0 && tmp->di_bwh <= dinfo->di_bstart)
				dinfo->di_bwh = tmp->di_bwh;
			if (inode)
//.........这里部分代码省略.........

static void*
cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
{
	struct dfs_info3_param *referrals = NULL;
	unsigned int num_referrals = 0;
	struct cifs_sb_info *cifs_sb;
	struct cifsSesInfo *ses;
	char *full_path = NULL;
	int xid, i;
	int rc = 0;
	struct vfsmount *mnt = ERR_PTR(-ENOENT);

	cFYI(1, ("in %s", __func__));
	BUG_ON(IS_ROOT(dentry));

	xid = GetXid();

	dput(nd->dentry);
	nd->dentry = dget(dentry);

	cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
	ses = cifs_sb->tcon->ses;

	if (!ses) {
		rc = -EINVAL;
		goto out_err;
	}

	/*
	 * The MSDFS spec states that paths in DFS referral requests and
	 * responses must be prefixed by a single '\' character instead of
	 * the double backslashes usually used in the UNC. This function
	 * gives us the latter, so we must adjust the result.
	 */
	full_path = build_path_from_dentry(dentry);
	if (full_path == NULL) {
		rc = -ENOMEM;
		goto out_err;
	}

	rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
		&num_referrals, &referrals,
		cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);

	for (i = 0; i < num_referrals; i++) {
		int len;
		dump_referral(referrals+i);
		/* connect to a node */
		len = strlen(referrals[i].node_name);
		if (len < 2) {
			cERROR(1, ("%s: Net Address path too short: %s",
					__func__, referrals[i].node_name));
			rc = -EINVAL;
			goto out_err;
		}
		mnt = cifs_dfs_do_refmount(nd->mnt,
				nd->dentry, referrals + i);
		cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
					referrals[i].node_name, mnt));

		/* complete mount procedure if we accured submount */
		if (!IS_ERR(mnt))
			break;
	}

	/* we need it cause for() above could exit without valid submount */
	rc = PTR_ERR(mnt);
	if (IS_ERR(mnt))
		goto out_err;

	rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);

out:
	FreeXid(xid);
	free_dfs_info_array(referrals, num_referrals);
	kfree(full_path);
	cFYI(1, ("leaving %s" , __func__));
	return ERR_PTR(rc);
out_err:
	path_release(nd);
	goto out;
}

/* create the sto dir, setup states */
int create_sto_dir(dentry_t *dentry, int mode)
{
	int err = 0;
	inode_t *dir;
	dentry_t *hidden_sto_dentry;
        dentry_t *hidden_sto_dir_dentry;

	/* had to take the "!S_ISDIR(mode))" check out, because it failed */
	if(exists_in_storage(dentry)) {
                printk(KERN_CRIT "mini_fo: create_sto_dir: wrong type or state.\\
n");
                err = -EINVAL;
                goto out;
        }

	err = get_neg_sto_dentry(dentry);
	if(err) {
		err = -EINVAL;
		goto out;
	}

	dir = dentry->d_parent->d_inode;
	hidden_sto_dentry = dtohd2(dentry);

	/* was: hidden_sto_dir_dentry = lock_parent(hidden_sto_dentry); */
	hidden_sto_dir_dentry = dget(hidden_sto_dentry->d_parent);

	err = PTR_ERR(hidden_sto_dir_dentry);
	if (IS_ERR(hidden_sto_dir_dentry))
		goto out;

	err = vfs_mkdir(hidden_sto_dir_dentry->d_inode,
			hidden_sto_dentry,
			mode);
	if(err) {
		printk(KERN_CRIT "mini_fo: create_sto_dir: ERROR creating sto dir.\n");
		goto out_lock;
	}

	if(!dtohd2(dentry)->d_inode) {
		printk(KERN_CRIT "mini_fo: create_sto_dir: ERROR creating sto dir [2].\n");
		err = -EINVAL;
		goto out_lock;
	}

	/* interpose the new inode */
	if(dtost(dentry) == DELETED) {
		dtost(dentry) = DEL_REWRITTEN;
		err = mini_fo_tri_interpose(NULL, hidden_sto_dentry, dentry, dir->i_sb, 0);
		if(err)
			goto out_lock;
	}
	else if(dtopd(dentry)->state == NON_EXISTANT) {
		dtopd(dentry)->state = CREATED;
		err = mini_fo_tri_interpose(dtohd(dentry), hidden_sto_dentry, dentry, dir->i_sb, 0);
		if(err)
			goto out_lock;
	}
	else if(dtopd(dentry)->state == UNMODIFIED) {
		dtopd(dentry)->state = MODIFIED;
		/* interpose on new inode */
		if(itohi2(dentry->d_inode) != NULL) {
			printk(KERN_CRIT "mini_fo:  create_sto_dir: ERROR, invalid inode detected.\n");
			err = -EINVAL;
			goto out_lock;
		}
		itohi2(dentry->d_inode) = igrab(dtohd2(dentry)->d_inode);
	}

	fist_copy_attr_timesizes(dir, hidden_sto_dir_dentry->d_inode);

	/* initalize the wol list */
	itopd(dentry->d_inode)->deleted_list_size = -1;
	itopd(dentry->d_inode)->renamed_list_size = -1;
	meta_build_lists(dentry);


 out_lock:
	/* was: unlock_dir(hidden_sto_dir_dentry); */
	dput(hidden_sto_dir_dentry);
 out:
	return err;
}