namei.c

linux 内核源代码

	}
	nls_name.hash = full_name_hash(nls_name.name, nls_name.len);

	/*
	 * Note: No need for dent->d_lock lock as i_mutex is held on the
	 * parent inode.
	 */

	/* Does a dentry matching the nls_name exist already? */
	real_dent = d_lookup(dent->d_parent, &nls_name);
	/* If not, create it now. */
	if (!real_dent) {
		real_dent = d_alloc(dent->d_parent, &nls_name);
		kfree(nls_name.name);
		if (!real_dent) {
			err = -ENOMEM;
			goto err_out;
		}
		new_dent = d_splice_alias(dent_inode, real_dent);
		if (new_dent)
			dput(real_dent);
		else
			new_dent = real_dent;
		ntfs_debug("Done.  (Created new dentry.)");
		return new_dent;
	}
	kfree(nls_name.name);
	/* Matching dentry exists, check if it is negative. */
	if (real_dent->d_inode) {
		if (unlikely(real_dent->d_inode != dent_inode)) {
			/* This can happen because bad inodes are unhashed. */
			BUG_ON(!is_bad_inode(dent_inode));
			BUG_ON(!is_bad_inode(real_dent->d_inode));
		}
		/*
		 * Already have the inode and the dentry attached, decrement
		 * the reference count to balance the ntfs_iget() we did
		 * earlier on.  We found the dentry using d_lookup() so it
		 * cannot be disconnected and thus we do not need to worry
		 * about any NFS/disconnectedness issues here.
		 */
		iput(dent_inode);
		ntfs_debug("Done.  (Already had inode and dentry.)");
		return real_dent;
	}
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
	 * has a 'disconnected' dentry (i.e. IS_ROOT and DCACHE_DISCONNECTED),
	 * in which case d_move() that in place of the found dentry.
	 */
	if (!S_ISDIR(dent_inode->i_mode)) {
		/* Not a directory; everything is easy. */
		d_instantiate(real_dent, dent_inode);
		ntfs_debug("Done.  (Already had negative file dentry.)");
		return real_dent;
	}
	spin_lock(&dcache_lock);
	if (list_empty(&dent_inode->i_dentry)) {
		/*
		 * Directory without a 'disconnected' dentry; we need to do
		 * d_instantiate() by hand because it takes dcache_lock which
		 * we already hold.
		 */
		list_add(&real_dent->d_alias, &dent_inode->i_dentry);
		real_dent->d_inode = dent_inode;
		spin_unlock(&dcache_lock);
		security_d_instantiate(real_dent, dent_inode);
		ntfs_debug("Done.  (Already had negative directory dentry.)");
		return real_dent;
	}
	/*
	 * Directory with a 'disconnected' dentry; get a reference to the
	 * 'disconnected' dentry.
	 */
	new_dent = list_entry(dent_inode->i_dentry.next, struct dentry,
			d_alias);
	dget_locked(new_dent);
	spin_unlock(&dcache_lock);
	/* Do security vodoo. */
	security_d_instantiate(real_dent, dent_inode);
	/* Move new_dent in place of real_dent. */
	d_move(new_dent, real_dent);
	/* Balance the ntfs_iget() we did above. */
	iput(dent_inode);
	/* Throw away real_dent. */
	dput(real_dent);
	/* Use new_dent as the actual dentry. */
	ntfs_debug("Done.  (Already had negative, disconnected directory "
			"dentry.)");
	return new_dent;

eio_err_out:
	ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
	err = -EIO;
err_out:
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (m)
		unmap_mft_record(ni);
	iput(dent_inode);
	ntfs_error(vol->sb, "Failed, returning error code %i.", err);
	return ERR_PTR(err);
   }
}

/**
 * Inode operations for directories.
 */
const struct inode_operations ntfs_dir_inode_ops = {
	.lookup	= ntfs_lookup,	/* VFS: Lookup directory. */
};

/**
 * ntfs_get_parent - find the dentry of the parent of a given directory dentry
 * @child_dent:		dentry of the directory whose parent directory to find
 *
 * Find the dentry for the parent directory of the directory specified by the
 * dentry @child_dent.  This function is called from
 * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
 * default ->decode_fh() which is export_decode_fh() in the same file.
 *
 * The code is based on the ext3 ->get_parent() implementation found in
 * fs/ext3/namei.c::ext3_get_parent().
 *
 * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_mutex down.
 *
 * Return the dentry of the parent directory on success or the error code on
 * error (IS_ERR() is true).
 */
static struct dentry *ntfs_get_parent(struct dentry *child_dent)
{
	struct inode *vi = child_dent->d_inode;
	ntfs_inode *ni = NTFS_I(vi);
	MFT_RECORD *mrec;
	ntfs_attr_search_ctx *ctx;
	ATTR_RECORD *attr;
	FILE_NAME_ATTR *fn;
	struct inode *parent_vi;
	struct dentry *parent_dent;
	unsigned long parent_ino;
	int err;

	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
	/* Get the mft record of the inode belonging to the child dentry. */
	mrec = map_mft_record(ni);
	if (IS_ERR(mrec))
		return (struct dentry *)mrec;
	/* Find the first file name attribute in the mft record. */
	ctx = ntfs_attr_get_search_ctx(ni, mrec);
	if (unlikely(!ctx)) {
		unmap_mft_record(ni);
		return ERR_PTR(-ENOMEM);
	}
try_next:
	err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
			0, ctx);
	if (unlikely(err)) {
		ntfs_attr_put_search_ctx(ctx);
		unmap_mft_record(ni);
		if (err == -ENOENT)
			ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
					"file name attribute.  Run chkdsk.",
					vi->i_ino);
		return ERR_PTR(err);
	}
	attr = ctx->attr;
	if (unlikely(attr->non_resident))
		goto try_next;
	fn = (FILE_NAME_ATTR *)((u8 *)attr +
			le16_to_cpu(attr->data.resident.value_offset));
	if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
			(u8*)attr + le32_to_cpu(attr->length)))
		goto try_next;
	/* Get the inode number of the parent directory. */
	parent_ino = MREF_LE(fn->parent_directory);
	/* Release the search context and the mft record of the child. */
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(ni);
	/* Get the inode of the parent directory. */
	parent_vi = ntfs_iget(vi->i_sb, parent_ino);
	if (IS_ERR(parent_vi) || unlikely(is_bad_inode(parent_vi))) {
		if (!IS_ERR(parent_vi))
			iput(parent_vi);
		ntfs_error(vi->i_sb, "Failed to get parent directory inode "
				"0x%lx of child inode 0x%lx.", parent_ino,
				vi->i_ino);
		return ERR_PTR(-EACCES);
	}
	/* Finally get a dentry for the parent directory and return it. */
	parent_dent = d_alloc_anon(parent_vi);
	if (unlikely(!parent_dent)) {
		iput(parent_vi);
		return ERR_PTR(-ENOMEM);
	}
	ntfs_debug("Done for inode 0x%lx.", vi->i_ino);
	return parent_dent;
}

static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
		u64 ino, u32 generation)
{
	struct inode *inode;

	inode = ntfs_iget(sb, ino);
	if (!IS_ERR(inode)) {
		if (is_bad_inode(inode) || inode->i_generation != generation) {
			iput(inode);
			inode = ERR_PTR(-ESTALE);
		}
	}

	return inode;
}

static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type)
{
	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
				    ntfs_nfs_get_inode);
}

static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type)
{
	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
				    ntfs_nfs_get_inode);
}

/**
 * Export operations allowing NFS exporting of mounted NTFS partitions.
 *
 * We use the default ->encode_fh() for now.  Note that they
 * use 32 bits to store the inode number which is an unsigned long so on 64-bit
 * architectures is usually 64 bits so it would all fail horribly on huge
 * volumes.  I guess we need to define our own encode and decode fh functions
 * that store 64-bit inode numbers at some point but for now we will ignore the
 * problem...
 *
 * We also use the default ->get_name() helper (used by ->decode_fh() via
 * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
 * independent.
 *
 * The default ->get_parent() just returns -EACCES so we have to provide our
 * own and the default ->get_dentry() is incompatible with NTFS due to not
 * allowing the inode number 0 which is used in NTFS for the system file $MFT
 * and due to using iget() whereas NTFS needs ntfs_iget().
 */
const struct export_operations ntfs_export_ops = {
	.get_parent	= ntfs_get_parent,	/* Find the parent of a given
						   directory. */
	.fh_to_dentry	= ntfs_fh_to_dentry,
	.fh_to_parent	= ntfs_fh_to_parent,
};