export_ops.c

/* Copyright 2005 by Hans Reiser, licensing governed by
 * reiser4/README */

#include "inode.h"
#include "plugin/plugin.h"

/*
 * Supported file-handle types
 */
typedef enum {
	FH_WITH_PARENT = 0x10,	/* file handle with parent */
	FH_WITHOUT_PARENT = 0x11	/* file handle without parent */
} reiser4_fhtype;

#define NFSERROR (255)

/* initialize place-holder for object */
static void object_on_wire_init(reiser4_object_on_wire *o)
{
	o->plugin = NULL;
}

/* finish with @o */
static void object_on_wire_done(reiser4_object_on_wire *o)
{
	if (o->plugin != NULL)
		o->plugin->wire.done(o);
}

/*
 * read serialized object identity from @addr and store information about
 * object in @obj. This is dual to encode_inode().
 */
static char *decode_inode(struct super_block *s, char *addr,
			  reiser4_object_on_wire * obj)
{
	file_plugin *fplug;

	/* identifier of object plugin is stored in the first two bytes,
	 * followed by... */
	fplug = file_plugin_by_disk_id(reiser4_get_tree(s), (d16 *) addr);
	if (fplug != NULL) {
		addr += sizeof(d16);
		obj->plugin = fplug;
		assert("nikita-3520", fplug->wire.read != NULL);
		/* plugin specific encoding of object identity. */
		addr = fplug->wire.read(addr, obj);
	} else
		addr = ERR_PTR(RETERR(-EINVAL));
	return addr;
}

static struct dentry *reiser4_get_dentry(struct super_block *super,
					 void *data);
/**
 * reiser4_decode_fh: decode on-wire object - helper function
 * for fh_to_dentry, fh_to_parent export operations;
 * @super: super block;
 * @addr: onwire object to be decoded;
 *
 * Returns dentry referring to the object being decoded.
 */
static struct dentry *reiser4_decode_fh(struct super_block * super,
					char * addr)
{
	reiser4_object_on_wire object;

	object_on_wire_init(&object);

	addr = decode_inode(super, addr, &object);
	if (!IS_ERR(addr)) {
		struct dentry *d;
		d = reiser4_get_dentry(super, &object);
		if (d != NULL && !IS_ERR(d))
			/* FIXME check for -ENOMEM */
			reiser4_get_dentry_fsdata(d)->stateless = 1;
		addr = (char *)d;
	}
	object_on_wire_done(&object);
	return (void *)addr;
}

static struct dentry *reiser4_fh_to_dentry(struct super_block *sb,
					   struct fid *fid,
					   int fh_len, int fh_type)
{
	reiser4_context *ctx;
	struct dentry *d;

	assert("edward-1536",
	       fh_type == FH_WITH_PARENT || fh_type == FH_WITHOUT_PARENT);

	ctx = reiser4_init_context(sb);
	if (IS_ERR(ctx))
		return (struct dentry *)ctx;

	d = reiser4_decode_fh(sb, (char *)fid->raw);

	reiser4_exit_context(ctx);
	return d;
}

static struct dentry *reiser4_fh_to_parent(struct super_block *sb,
					   struct fid *fid,
					   int fh_len, int fh_type)
{
	char * addr;
	struct dentry * d;
	reiser4_context *ctx;
	file_plugin *fplug;

	if (fh_type == FH_WITHOUT_PARENT)
		return NULL;
	assert("edward-1537", fh_type == FH_WITH_PARENT);

	ctx = reiser4_init_context(sb);
	if (IS_ERR(ctx))
		return (struct dentry *)ctx;
	addr = (char *)fid->raw;
	/* extract 2-bytes file plugin id */
	fplug = file_plugin_by_disk_id(reiser4_get_tree(sb), (d16 *)addr);
	if (fplug == NULL) {
		d = ERR_PTR(RETERR(-EINVAL));
		goto exit;
	}
	addr += sizeof(d16);
	/* skip previously encoded object */
	addr = fplug->wire.read(addr, NULL /* skip */);
	if (IS_ERR(addr)) {
		d = (struct dentry *)addr;
		goto exit;
	}
	/* @extract and decode parent object */
	d = reiser4_decode_fh(sb, addr);
 exit:
	reiser4_exit_context(ctx);
	return d;
}

/*
 * Object serialization support.
 *
 * To support knfsd file system provides export_operations that are used to
 * construct and interpret NFS file handles. As a generalization of this,
 * reiser4 object plugins have serialization support: it provides methods to
 * create on-wire representation of identity of reiser4 object, and
 * re-create/locate object given its on-wire identity.
 *
 */

/*
 * return number of bytes that on-wire representation of @inode's identity
 * consumes.
 */
static int encode_inode_size(struct inode *inode)
{
	assert("nikita-3514", inode != NULL);
	assert("nikita-3515", inode_file_plugin(inode) != NULL);
	assert("nikita-3516", inode_file_plugin(inode)->wire.size != NULL);

	return inode_file_plugin(inode)->wire.size(inode) + sizeof(d16);
}

/*
 * store on-wire representation of @inode's identity at the area beginning at
 * @start.
 */
static char *encode_inode(struct inode *inode, char *start)
{
	assert("nikita-3517", inode != NULL);
	assert("nikita-3518", inode_file_plugin(inode) != NULL);
	assert("nikita-3519", inode_file_plugin(inode)->wire.write != NULL);

	/*
	 * first, store two-byte identifier of object plugin, then
	 */
	save_plugin_id(file_plugin_to_plugin(inode_file_plugin(inode)),
		       (d16 *) start);
	start += sizeof(d16);
	/*
	 * call plugin to serialize object's identity
	 */
	return inode_file_plugin(inode)->wire.write(inode, start);
}

/* this returns number of 32 bit long numbers encoded in @lenp. 255 is
 * returned if file handle can not be stored */
/**
 * reiser4_encode_fh - encode_fh of export operations
 * @dentry:
 * @fh:
 * @lenp:
 * @need_parent:
 *
 */
static int
reiser4_encode_fh(struct inode *inode, __u32 *fh, int *lenp,
		  struct inode *parent)
{
	char *addr;
	int need;
	int delta;
	int result;
	bool need_parent;
	reiser4_context *ctx;

	/*
	 * knfsd asks as to serialize @inode, and, optionally its
	 * parent @parent (if it is non-NULL).
	 *
	 * encode_inode() and encode_inode_size() is used to build
	 * representation of object and its parent. All hard work is done by
	 * object plugins.
	 */
	need_parent = (parent != NULL);
	addr = (char *)fh;

	need = encode_inode_size(inode);
	if (need < 0)
		return NFSERROR;
	if (need_parent) {
		delta = encode_inode_size(parent);
		if (delta < 0)
			return NFSERROR;
		need += delta;
	}

	ctx = reiser4_init_context(inode->i_sb);
	if (IS_ERR(ctx))
		return PTR_ERR(ctx);

	if (need <= sizeof(__u32) * (*lenp)) {
		addr = encode_inode(inode, addr);
		if (need_parent)
			addr = encode_inode(parent, addr);

		/* store in lenp number of 32bit words required for file
		 * handle. */
		*lenp = (need + sizeof(__u32) - 1) >> 2;
		result = need_parent ? FH_WITH_PARENT : FH_WITHOUT_PARENT;
	} else
		/* no enough space in file handle */
		result = NFSERROR;
	reiser4_exit_context(ctx);
	return result;
}

/**
 * reiser4_get_dentry_parent - get_parent of export operations
 * @child:
 *
 */
static struct dentry *reiser4_get_dentry_parent(struct dentry *child)
{
	struct inode *dir;
	dir_plugin *dplug;
	struct dentry *result;
	reiser4_context *ctx;

	assert("nikita-3527", child != NULL);

	dir = child->d_inode;
	assert("nikita-3529", dir != NULL);

	ctx = reiser4_init_context(dir->i_sb);
	if (IS_ERR(ctx))
		return (void *)ctx;

	dplug = inode_dir_plugin(dir);
	assert("nikita-3531", ergo(dplug != NULL, dplug->get_parent != NULL));

	if (unlikely(dplug == NULL)) {
		reiser4_exit_context(ctx);
		return ERR_PTR(RETERR(-ENOTDIR));
	}
	result = dplug->get_parent(dir);
	reiser4_exit_context(ctx);
	return result;
}

/**
 * reiser4_get_dentry - get_dentry of export operations
 * @super:
 * @data:
 *
 *
 */
static struct dentry *reiser4_get_dentry(struct super_block *super, void *data)
{
	reiser4_object_on_wire *o;

	assert("nikita-3522", super != NULL);
	assert("nikita-3523", data != NULL);
	/*
	 * this is only supposed to be called by
	 *
	 *     reiser4_decode_fh->find_exported_dentry
	 *
	 * so, reiser4_context should be here already.
	 */
	assert("nikita-3526", is_in_reiser4_context());

	o = (reiser4_object_on_wire *)data;
	assert("nikita-3524", o->plugin != NULL);
	assert("nikita-3525", o->plugin->wire.get != NULL);

	return o->plugin->wire.get(super, o);
}

struct export_operations reiser4_export_operations = {
	.encode_fh = reiser4_encode_fh,
	.fh_to_dentry = reiser4_fh_to_dentry,
	.fh_to_parent = reiser4_fh_to_parent,
	.get_parent = reiser4_get_dentry_parent,
};

/*
 * Local variables:
 * c-indentation-style: "K&R"
 * mode-name: "LC"
 * c-basic-offset: 8
 * tab-width: 8
 * fill-column: 79
 * End:
 */