drivers/staging/lustre/lnet/lnet/lib-md.c - arm/linux - Git at Google

 /*
  * GPL HEADER START
  *
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 only,
  * as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License version 2 for more details (a copy is included
  * in the LICENSE file that accompanied this code).
  *
  * You should have received a copy of the GNU General Public License
  * version 2 along with this program; If not, see
  * http://www.gnu.org/licenses/gpl-2.0.html
  *
  * GPL HEADER END
  */
 /*
  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
  * Use is subject to license terms.
  *
  * Copyright (c) 2012, Intel Corporation.
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
  * Lustre is a trademark of Sun Microsystems, Inc.
  *
  * lnet/lnet/lib-md.c
  *
  * Memory Descriptor management routines
  */

 #define DEBUG_SUBSYSTEM S_LNET

 #include <linux/lnet/lib-lnet.h>

 /* must be called with lnet_res_lock held */
 void
 lnet_md_unlink(struct lnet_libmd *md)
 {
 	if (!(md->md_flags & LNET_MD_FLAG_ZOMBIE)) {
 		/* first unlink attempt... */
 		struct lnet_me *me = md->md_me;

 		md->md_flags |= LNET_MD_FLAG_ZOMBIE;

 		/*
 		 * Disassociate from ME (if any),
 		 * and unlink it if it was created
 		 * with LNET_UNLINK
 		 */
 		if (me) {
 			/* detach MD from portal */
 			lnet_ptl_detach_md(me, md);
 			if (me->me_unlink == LNET_UNLINK)
 				lnet_me_unlink(me);
 		}

 		/* ensure all future handle lookups fail */
 		lnet_res_lh_invalidate(&md->md_lh);
 	}

 	if (md->md_refcount) {
 		CDEBUG(D_NET, "Queueing unlink of md %p\n", md);
 		return;
 	}

 	CDEBUG(D_NET, "Unlinking md %p\n", md);

 	if (md->md_eq) {
 		int cpt = lnet_cpt_of_cookie(md->md_lh.lh_cookie);

 		LASSERT(*md->md_eq->eq_refs[cpt] > 0);
 		(*md->md_eq->eq_refs[cpt])--;
 	}

 	LASSERT(!list_empty(&md->md_list));
 	list_del_init(&md->md_list);
 	lnet_md_free(md);
 }

 static int
 lnet_md_build(struct lnet_libmd *lmd, struct lnet_md *umd, int unlink)
 {
 	int i;
 	unsigned int niov;
 	int total_length = 0;

 	lmd->md_me = NULL;
 	lmd->md_start = umd->start;
 	lmd->md_offset = 0;
 	lmd->md_max_size = umd->max_size;
 	lmd->md_options = umd->options;
 	lmd->md_user_ptr = umd->user_ptr;
 	lmd->md_eq = NULL;
 	lmd->md_threshold = umd->threshold;
 	lmd->md_refcount = 0;
 	lmd->md_flags = (unlink == LNET_UNLINK) ? LNET_MD_FLAG_AUTO_UNLINK : 0;

 	if (umd->options & LNET_MD_IOVEC) {
 		if (umd->options & LNET_MD_KIOV) /* Can't specify both */
 			return -EINVAL;

 		niov = umd->length;
 		lmd->md_niov = umd->length;
 		memcpy(lmd->md_iov.iov, umd->start,
 		       niov * sizeof(lmd->md_iov.iov[0]));

 		for (i = 0; i < (int)niov; i++) {
 			/* We take the base address on trust */
 			/* invalid length */
 			if (lmd->md_iov.iov[i].iov_len <= 0)
 				return -EINVAL;

 			total_length += lmd->md_iov.iov[i].iov_len;
 		}

 		lmd->md_length = total_length;

 		if ((umd->options & LNET_MD_MAX_SIZE) && /* use max size */
 		    (umd->max_size < 0 ||
 		     umd->max_size > total_length)) /* illegal max_size */
 			return -EINVAL;

 	} else if (umd->options & LNET_MD_KIOV) {
 		niov = umd->length;
 		lmd->md_niov = umd->length;
 		memcpy(lmd->md_iov.kiov, umd->start,
 		       niov * sizeof(lmd->md_iov.kiov[0]));

 		for (i = 0; i < (int)niov; i++) {
 			/* We take the page pointer on trust */
 			if (lmd->md_iov.kiov[i].bv_offset +
 			    lmd->md_iov.kiov[i].bv_len > PAGE_SIZE)
 				return -EINVAL; /* invalid length */

 			total_length += lmd->md_iov.kiov[i].bv_len;
 		}

 		lmd->md_length = total_length;

 		if ((umd->options & LNET_MD_MAX_SIZE) && /* max size used */
 		    (umd->max_size < 0 ||
 		     umd->max_size > total_length)) /* illegal max_size */
 			return -EINVAL;
 	} else {   /* contiguous */
 		lmd->md_length = umd->length;
 		niov = 1;
 		lmd->md_niov = 1;
 		lmd->md_iov.iov[0].iov_base = umd->start;
 		lmd->md_iov.iov[0].iov_len = umd->length;

 		if ((umd->options & LNET_MD_MAX_SIZE) && /* max size used */
 		    (umd->max_size < 0 ||
 		     umd->max_size > (int)umd->length)) /* illegal max_size */
 			return -EINVAL;
 	}

 	return 0;
 }

 /* must be called with resource lock held */
 static int
 lnet_md_link(struct lnet_libmd *md, struct lnet_handle_eq eq_handle, int cpt)
 {
 	struct lnet_res_container *container = the_lnet.ln_md_containers[cpt];

 	/*
 	 * NB we are passed an allocated, but inactive md.
 	 * if we return success, caller may lnet_md_unlink() it.
 	 * otherwise caller may only lnet_md_free() it.
 	 */
 	/*
 	 * This implementation doesn't know how to create START events or
 	 * disable END events.  Best to LASSERT our caller is compliant so
 	 * we find out quickly...
 	 */
 	/*
 	 * TODO - reevaluate what should be here in light of
 	 * the removal of the start and end events
 	 * maybe there we shouldn't even allow LNET_EQ_NONE!)
 	 * LASSERT(!eq);
 	 */
 	if (!LNetEQHandleIsInvalid(eq_handle)) {
 		md->md_eq = lnet_handle2eq(&eq_handle);

 		if (!md->md_eq)
 			return -ENOENT;

 		(*md->md_eq->eq_refs[cpt])++;
 	}

 	lnet_res_lh_initialize(container, &md->md_lh);

 	LASSERT(list_empty(&md->md_list));
 	list_add(&md->md_list, &container->rec_active);

 	return 0;
 }

 /* must be called with lnet_res_lock held */
 void
 lnet_md_deconstruct(struct lnet_libmd *lmd, struct lnet_md *umd)
 {
 	/* NB this doesn't copy out all the iov entries so when a
 	 * discontiguous MD is copied out, the target gets to know the
 	 * original iov pointer (in start) and the number of entries it had
 	 * and that's all.
 	 */
 	umd->start = lmd->md_start;
 	umd->length = !(lmd->md_options &
 		      (LNET_MD_IOVEC | LNET_MD_KIOV)) ?
 		      lmd->md_length : lmd->md_niov;
 	umd->threshold = lmd->md_threshold;
 	umd->max_size = lmd->md_max_size;
 	umd->options = lmd->md_options;
 	umd->user_ptr = lmd->md_user_ptr;
 	lnet_eq2handle(&umd->eq_handle, lmd->md_eq);
 }

 static int
 lnet_md_validate(struct lnet_md *umd)
 {
 	if (!umd->start && umd->length) {
 		CERROR("MD start pointer can not be NULL with length %u\n",
 		       umd->length);
 		return -EINVAL;
 	}

 	if ((umd->options & (LNET_MD_KIOV | LNET_MD_IOVEC)) &&
 	    umd->length > LNET_MAX_IOV) {
 		CERROR("Invalid option: too many fragments %u, %d max\n",
 		       umd->length, LNET_MAX_IOV);
 		return -EINVAL;
 	}

 	return 0;
 }

 /**
  * Create a memory descriptor and attach it to a ME
  *
  * \param meh A handle for a ME to associate the new MD with.
  * \param umd Provides initial values for the user-visible parts of a MD.
  * Other than its use for initialization, there is no linkage between this
  * structure and the MD maintained by the LNet.
  * \param unlink A flag to indicate whether the MD is automatically unlinked
  * when it becomes inactive, either because the operation threshold drops to
  * zero or because the available memory becomes less than \a umd.max_size.
  * (Note that the check for unlinking a MD only occurs after the completion
  * of a successful operation on the MD.) The value LNET_UNLINK enables auto
  * unlinking; the value LNET_RETAIN disables it.
  * \param handle On successful returns, a handle to the newly created MD is
  * saved here. This handle can be used later in LNetMDUnlink().
  *
  * \retval 0       On success.
  * \retval -EINVAL If \a umd is not valid.
  * \retval -ENOMEM If new MD cannot be allocated.
  * \retval -ENOENT Either \a meh or \a umd.eq_handle does not point to a
  * valid object. Note that it's OK to supply a NULL \a umd.eq_handle by
  * calling LNetInvalidateHandle() on it.
  * \retval -EBUSY  If the ME pointed to by \a meh is already associated with
  * a MD.
  */
 int
 LNetMDAttach(struct lnet_handle_me meh, struct lnet_md umd,
 	     enum lnet_unlink unlink, struct lnet_handle_md *handle)
 {
 	LIST_HEAD(matches);
 	LIST_HEAD(drops);
 	struct lnet_me *me;
 	struct lnet_libmd *md;
 	int cpt;
 	int rc;

 	LASSERT(the_lnet.ln_refcount > 0);

 	if (lnet_md_validate(&umd))
 		return -EINVAL;

 	if (!(umd.options & (LNET_MD_OP_GET | LNET_MD_OP_PUT))) {
 		CERROR("Invalid option: no MD_OP set\n");
 		return -EINVAL;
 	}

 	md = lnet_md_alloc(&umd);
 	if (!md)
 		return -ENOMEM;

 	rc = lnet_md_build(md, &umd, unlink);
 	if (rc)
 		goto out_free;

 	cpt = lnet_cpt_of_cookie(meh.cookie);

 	lnet_res_lock(cpt);

 	me = lnet_handle2me(&meh);
 	if (!me)
 		rc = -ENOENT;
 	else if (me->me_md)
 		rc = -EBUSY;
 	else
 		rc = lnet_md_link(md, umd.eq_handle, cpt);

 	if (rc)
 		goto out_unlock;

 	/*
 	 * attach this MD to portal of ME and check if it matches any
 	 * blocked msgs on this portal
 	 */
 	lnet_ptl_attach_md(me, md, &matches, &drops);

 	lnet_md2handle(handle, md);

 	lnet_res_unlock(cpt);

 	lnet_drop_delayed_msg_list(&drops, "Bad match");
 	lnet_recv_delayed_msg_list(&matches);

 	return 0;

 out_unlock:
 	lnet_res_unlock(cpt);
 out_free:
 	lnet_md_free(md);
 	return rc;
 }
 EXPORT_SYMBOL(LNetMDAttach);

 /**
  * Create a "free floating" memory descriptor - a MD that is not associated
  * with a ME. Such MDs are usually used in LNetPut() and LNetGet() operations.
  *
  * \param umd,unlink See the discussion for LNetMDAttach().
  * \param handle On successful returns, a handle to the newly created MD is
  * saved here. This handle can be used later in LNetMDUnlink(), LNetPut(),
  * and LNetGet() operations.
  *
  * \retval 0       On success.
  * \retval -EINVAL If \a umd is not valid.
  * \retval -ENOMEM If new MD cannot be allocated.
  * \retval -ENOENT \a umd.eq_handle does not point to a valid EQ. Note that
  * it's OK to supply a NULL \a umd.eq_handle by calling
  * LNetInvalidateHandle() on it.
  */
 int
 LNetMDBind(struct lnet_md umd, enum lnet_unlink unlink,
 	   struct lnet_handle_md *handle)
 {
 	struct lnet_libmd *md;
 	int cpt;
 	int rc;

 	LASSERT(the_lnet.ln_refcount > 0);

 	if (lnet_md_validate(&umd))
 		return -EINVAL;

 	if ((umd.options & (LNET_MD_OP_GET | LNET_MD_OP_PUT))) {
 		CERROR("Invalid option: GET|PUT illegal on active MDs\n");
 		return -EINVAL;
 	}

 	md = lnet_md_alloc(&umd);
 	if (!md)
 		return -ENOMEM;

 	rc = lnet_md_build(md, &umd, unlink);
 	if (rc)
 		goto out_free;

 	cpt = lnet_res_lock_current();

 	rc = lnet_md_link(md, umd.eq_handle, cpt);
 	if (rc)
 		goto out_unlock;

 	lnet_md2handle(handle, md);

 	lnet_res_unlock(cpt);
 	return 0;

 out_unlock:
 	lnet_res_unlock(cpt);
 out_free:
 	lnet_md_free(md);

 	return rc;
 }
 EXPORT_SYMBOL(LNetMDBind);

 /**
  * Unlink the memory descriptor from any ME it may be linked to and release
  * the internal resources associated with it. As a result, active messages
  * associated with the MD may get aborted.
  *
  * This function does not free the memory region associated with the MD;
  * i.e., the memory the user allocated for this MD. If the ME associated with
  * this MD is not NULL and was created with auto unlink enabled, the ME is
  * unlinked as well (see LNetMEAttach()).
  *
  * Explicitly unlinking a MD via this function call has the same behavior as
  * a MD that has been automatically unlinked, except that no LNET_EVENT_UNLINK
  * is generated in the latter case.
  *
  * An unlinked event can be reported in two ways:
  * - If there's no pending operations on the MD, it's unlinked immediately
  *   and an LNET_EVENT_UNLINK event is logged before this function returns.
  * - Otherwise, the MD is only marked for deletion when this function
  *   returns, and the unlinked event will be piggybacked on the event of
  *   the completion of the last operation by setting the unlinked field of
  *   the event. No dedicated LNET_EVENT_UNLINK event is generated.
  *
  * Note that in both cases the unlinked field of the event is always set; no
  * more event will happen on the MD after such an event is logged.
  *
  * \param mdh A handle for the MD to be unlinked.
  *
  * \retval 0       On success.
  * \retval -ENOENT If \a mdh does not point to a valid MD object.
  */
 int
 LNetMDUnlink(struct lnet_handle_md mdh)
 {
 	struct lnet_event ev;
 	struct lnet_libmd *md;
 	int cpt;

 	LASSERT(the_lnet.ln_refcount > 0);

 	cpt = lnet_cpt_of_cookie(mdh.cookie);
 	lnet_res_lock(cpt);

 	md = lnet_handle2md(&mdh);
 	if (!md) {
 		lnet_res_unlock(cpt);
 		return -ENOENT;
 	}

 	md->md_flags |= LNET_MD_FLAG_ABORTED;
 	/*
 	 * If the MD is busy, lnet_md_unlink just marks it for deletion, and
 	 * when the LND is done, the completion event flags that the MD was
 	 * unlinked.  Otherwise, we enqueue an event now...
 	 */
 	if (md->md_eq && !md->md_refcount) {
 		lnet_build_unlink_event(md, &ev);
 		lnet_eq_enqueue_event(md->md_eq, &ev);
 	}

 	lnet_md_unlink(md);

 	lnet_res_unlock(cpt);
 	return 0;
 }
 EXPORT_SYMBOL(LNetMDUnlink);
	/*
	* GPL HEADER START
	*
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 only,
	* as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License version 2 for more details (a copy is included
	* in the LICENSE file that accompanied this code).
	*
	* You should have received a copy of the GNU General Public License
	* version 2 along with this program; If not, see
	* http://www.gnu.org/licenses/gpl-2.0.html
	*
	* GPL HEADER END
	*/
	/*
	* Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
	* Use is subject to license terms.
	*
	* Copyright (c) 2012, Intel Corporation.
	*/
	/*
	* This file is part of Lustre, http://www.lustre.org/
	* Lustre is a trademark of Sun Microsystems, Inc.
	*
	* lnet/lnet/lib-md.c
	*
	* Memory Descriptor management routines
	*/

	#define DEBUG_SUBSYSTEM S_LNET

	#include <linux/lnet/lib-lnet.h>

	/* must be called with lnet_res_lock held */
	void
	lnet_md_unlink(struct lnet_libmd *md)
	{
	if (!(md->md_flags & LNET_MD_FLAG_ZOMBIE)) {
	/* first unlink attempt... */
	struct lnet_me *me = md->md_me;

	md->md_flags \|= LNET_MD_FLAG_ZOMBIE;

	/*
	* Disassociate from ME (if any),
	* and unlink it if it was created
	* with LNET_UNLINK
	*/
	if (me) {
	/* detach MD from portal */
	lnet_ptl_detach_md(me, md);
	if (me->me_unlink == LNET_UNLINK)
	lnet_me_unlink(me);
	}

	/* ensure all future handle lookups fail */
	lnet_res_lh_invalidate(&md->md_lh);
	}

	if (md->md_refcount) {
	CDEBUG(D_NET, "Queueing unlink of md %p\n", md);
	return;
	}

	CDEBUG(D_NET, "Unlinking md %p\n", md);

	if (md->md_eq) {
	int cpt = lnet_cpt_of_cookie(md->md_lh.lh_cookie);

	LASSERT(*md->md_eq->eq_refs[cpt] > 0);
	(*md->md_eq->eq_refs[cpt])--;
	}

	LASSERT(!list_empty(&md->md_list));
	list_del_init(&md->md_list);
	lnet_md_free(md);
	}

	static int
	lnet_md_build(struct lnet_libmd lmd, struct lnet_md umd, int unlink)
	{
	int i;
	unsigned int niov;
	int total_length = 0;

	lmd->md_me = NULL;
	lmd->md_start = umd->start;
	lmd->md_offset = 0;
	lmd->md_max_size = umd->max_size;
	lmd->md_options = umd->options;
	lmd->md_user_ptr = umd->user_ptr;
	lmd->md_eq = NULL;
	lmd->md_threshold = umd->threshold;
	lmd->md_refcount = 0;
	lmd->md_flags = (unlink == LNET_UNLINK) ? LNET_MD_FLAG_AUTO_UNLINK : 0;

	if (umd->options & LNET_MD_IOVEC) {
	if (umd->options & LNET_MD_KIOV) /* Can't specify both */
	return -EINVAL;

	niov = umd->length;
	lmd->md_niov = umd->length;
	memcpy(lmd->md_iov.iov, umd->start,
	niov * sizeof(lmd->md_iov.iov[0]));

	for (i = 0; i < (int)niov; i++) {
	/* We take the base address on trust */
	/* invalid length */
	if (lmd->md_iov.iov[i].iov_len <= 0)
	return -EINVAL;

	total_length += lmd->md_iov.iov[i].iov_len;
	}

	lmd->md_length = total_length;

	if ((umd->options & LNET_MD_MAX_SIZE) && /* use max size */
	(umd->max_size < 0 \|\|
	umd->max_size > total_length)) /* illegal max_size */
	return -EINVAL;

	} else if (umd->options & LNET_MD_KIOV) {
	niov = umd->length;
	lmd->md_niov = umd->length;
	memcpy(lmd->md_iov.kiov, umd->start,
	niov * sizeof(lmd->md_iov.kiov[0]));

	for (i = 0; i < (int)niov; i++) {
	/* We take the page pointer on trust */
	if (lmd->md_iov.kiov[i].bv_offset +
	lmd->md_iov.kiov[i].bv_len > PAGE_SIZE)
	return -EINVAL; /* invalid length */

	total_length += lmd->md_iov.kiov[i].bv_len;
	}

	lmd->md_length = total_length;

	if ((umd->options & LNET_MD_MAX_SIZE) && /* max size used */
	(umd->max_size < 0 \|\|
	umd->max_size > total_length)) /* illegal max_size */
	return -EINVAL;
	} else { /* contiguous */
	lmd->md_length = umd->length;
	niov = 1;
	lmd->md_niov = 1;
	lmd->md_iov.iov[0].iov_base = umd->start;
	lmd->md_iov.iov[0].iov_len = umd->length;

	if ((umd->options & LNET_MD_MAX_SIZE) && /* max size used */
	(umd->max_size < 0 \|\|
	umd->max_size > (int)umd->length)) /* illegal max_size */
	return -EINVAL;
	}

	return 0;
	}

	/* must be called with resource lock held */
	static int
	lnet_md_link(struct lnet_libmd *md, struct lnet_handle_eq eq_handle, int cpt)
	{
	struct lnet_res_container *container = the_lnet.ln_md_containers[cpt];

	/*
	* NB we are passed an allocated, but inactive md.
	* if we return success, caller may lnet_md_unlink() it.
	* otherwise caller may only lnet_md_free() it.
	*/
	/*
	* This implementation doesn't know how to create START events or
	* disable END events. Best to LASSERT our caller is compliant so
	* we find out quickly...
	*/
	/*
	* TODO - reevaluate what should be here in light of
	* the removal of the start and end events
	* maybe there we shouldn't even allow LNET_EQ_NONE!)
	* LASSERT(!eq);
	*/
	if (!LNetEQHandleIsInvalid(eq_handle)) {
	md->md_eq = lnet_handle2eq(&eq_handle);

	if (!md->md_eq)
	return -ENOENT;

	(*md->md_eq->eq_refs[cpt])++;
	}

	lnet_res_lh_initialize(container, &md->md_lh);

	LASSERT(list_empty(&md->md_list));
	list_add(&md->md_list, &container->rec_active);

	return 0;
	}

	/* must be called with lnet_res_lock held */
	void
	lnet_md_deconstruct(struct lnet_libmd lmd, struct lnet_md umd)
	{
	/* NB this doesn't copy out all the iov entries so when a
	* discontiguous MD is copied out, the target gets to know the
	* original iov pointer (in start) and the number of entries it had
	* and that's all.
	*/
	umd->start = lmd->md_start;
	umd->length = !(lmd->md_options &
	(LNET_MD_IOVEC \| LNET_MD_KIOV)) ?
	lmd->md_length : lmd->md_niov;
	umd->threshold = lmd->md_threshold;
	umd->max_size = lmd->md_max_size;
	umd->options = lmd->md_options;
	umd->user_ptr = lmd->md_user_ptr;
	lnet_eq2handle(&umd->eq_handle, lmd->md_eq);
	}

	static int
	lnet_md_validate(struct lnet_md *umd)
	{
	if (!umd->start && umd->length) {
	CERROR("MD start pointer can not be NULL with length %u\n",
	umd->length);
	return -EINVAL;
	}

	if ((umd->options & (LNET_MD_KIOV \| LNET_MD_IOVEC)) &&
	umd->length > LNET_MAX_IOV) {
	CERROR("Invalid option: too many fragments %u, %d max\n",
	umd->length, LNET_MAX_IOV);
	return -EINVAL;
	}

	return 0;
	}

	/**
	* Create a memory descriptor and attach it to a ME
	*
	* \param meh A handle for a ME to associate the new MD with.
	* \param umd Provides initial values for the user-visible parts of a MD.
	* Other than its use for initialization, there is no linkage between this
	* structure and the MD maintained by the LNet.
	* \param unlink A flag to indicate whether the MD is automatically unlinked
	* when it becomes inactive, either because the operation threshold drops to
	* zero or because the available memory becomes less than \a umd.max_size.
	* (Note that the check for unlinking a MD only occurs after the completion
	* of a successful operation on the MD.) The value LNET_UNLINK enables auto
	* unlinking; the value LNET_RETAIN disables it.
	* \param handle On successful returns, a handle to the newly created MD is
	* saved here. This handle can be used later in LNetMDUnlink().
	*
	* \retval 0 On success.
	* \retval -EINVAL If \a umd is not valid.
	* \retval -ENOMEM If new MD cannot be allocated.
	* \retval -ENOENT Either \a meh or \a umd.eq_handle does not point to a
	* valid object. Note that it's OK to supply a NULL \a umd.eq_handle by
	* calling LNetInvalidateHandle() on it.
	* \retval -EBUSY If the ME pointed to by \a meh is already associated with
	* a MD.
	*/
	int
	LNetMDAttach(struct lnet_handle_me meh, struct lnet_md umd,
	enum lnet_unlink unlink, struct lnet_handle_md *handle)
	{
	LIST_HEAD(matches);
	LIST_HEAD(drops);
	struct lnet_me *me;
	struct lnet_libmd *md;
	int cpt;
	int rc;

	LASSERT(the_lnet.ln_refcount > 0);

	if (lnet_md_validate(&umd))
	return -EINVAL;

	if (!(umd.options & (LNET_MD_OP_GET \| LNET_MD_OP_PUT))) {
	CERROR("Invalid option: no MD_OP set\n");
	return -EINVAL;
	}

	md = lnet_md_alloc(&umd);
	if (!md)
	return -ENOMEM;

	rc = lnet_md_build(md, &umd, unlink);
	if (rc)
	goto out_free;

	cpt = lnet_cpt_of_cookie(meh.cookie);

	lnet_res_lock(cpt);

	me = lnet_handle2me(&meh);
	if (!me)
	rc = -ENOENT;
	else if (me->me_md)
	rc = -EBUSY;
	else
	rc = lnet_md_link(md, umd.eq_handle, cpt);

	if (rc)
	goto out_unlock;

	/*
	* attach this MD to portal of ME and check if it matches any
	* blocked msgs on this portal
	*/
	lnet_ptl_attach_md(me, md, &matches, &drops);

	lnet_md2handle(handle, md);

	lnet_res_unlock(cpt);

	lnet_drop_delayed_msg_list(&drops, "Bad match");
	lnet_recv_delayed_msg_list(&matches);

	return 0;

	out_unlock:
	lnet_res_unlock(cpt);
	out_free:
	lnet_md_free(md);
	return rc;
	}
	EXPORT_SYMBOL(LNetMDAttach);

	/**
	* Create a "free floating" memory descriptor - a MD that is not associated
	* with a ME. Such MDs are usually used in LNetPut() and LNetGet() operations.
	*
	* \param umd,unlink See the discussion for LNetMDAttach().
	* \param handle On successful returns, a handle to the newly created MD is
	* saved here. This handle can be used later in LNetMDUnlink(), LNetPut(),
	* and LNetGet() operations.
	*
	* \retval 0 On success.
	* \retval -EINVAL If \a umd is not valid.
	* \retval -ENOMEM If new MD cannot be allocated.
	* \retval -ENOENT \a umd.eq_handle does not point to a valid EQ. Note that
	* it's OK to supply a NULL \a umd.eq_handle by calling
	* LNetInvalidateHandle() on it.
	*/
	int
	LNetMDBind(struct lnet_md umd, enum lnet_unlink unlink,
	struct lnet_handle_md *handle)
	{
	struct lnet_libmd *md;
	int cpt;
	int rc;

	LASSERT(the_lnet.ln_refcount > 0);

	if (lnet_md_validate(&umd))
	return -EINVAL;

	if ((umd.options & (LNET_MD_OP_GET \| LNET_MD_OP_PUT))) {
	CERROR("Invalid option: GET\|PUT illegal on active MDs\n");
	return -EINVAL;
	}

	md = lnet_md_alloc(&umd);
	if (!md)
	return -ENOMEM;

	rc = lnet_md_build(md, &umd, unlink);
	if (rc)
	goto out_free;

	cpt = lnet_res_lock_current();

	rc = lnet_md_link(md, umd.eq_handle, cpt);
	if (rc)
	goto out_unlock;

	lnet_md2handle(handle, md);

	lnet_res_unlock(cpt);
	return 0;

	out_unlock:
	lnet_res_unlock(cpt);
	out_free:
	lnet_md_free(md);

	return rc;
	}
	EXPORT_SYMBOL(LNetMDBind);

	/**
	* Unlink the memory descriptor from any ME it may be linked to and release
	* the internal resources associated with it. As a result, active messages
	* associated with the MD may get aborted.
	*
	* This function does not free the memory region associated with the MD;
	* i.e., the memory the user allocated for this MD. If the ME associated with
	* this MD is not NULL and was created with auto unlink enabled, the ME is
	* unlinked as well (see LNetMEAttach()).
	*
	* Explicitly unlinking a MD via this function call has the same behavior as
	* a MD that has been automatically unlinked, except that no LNET_EVENT_UNLINK
	* is generated in the latter case.
	*
	* An unlinked event can be reported in two ways:
	* - If there's no pending operations on the MD, it's unlinked immediately
	* and an LNET_EVENT_UNLINK event is logged before this function returns.
	* - Otherwise, the MD is only marked for deletion when this function
	* returns, and the unlinked event will be piggybacked on the event of
	* the completion of the last operation by setting the unlinked field of
	* the event. No dedicated LNET_EVENT_UNLINK event is generated.
	*
	* Note that in both cases the unlinked field of the event is always set; no
	* more event will happen on the MD after such an event is logged.
	*
	* \param mdh A handle for the MD to be unlinked.
	*
	* \retval 0 On success.
	* \retval -ENOENT If \a mdh does not point to a valid MD object.
	*/
	int
	LNetMDUnlink(struct lnet_handle_md mdh)
	{
	struct lnet_event ev;
	struct lnet_libmd *md;
	int cpt;

	LASSERT(the_lnet.ln_refcount > 0);

	cpt = lnet_cpt_of_cookie(mdh.cookie);
	lnet_res_lock(cpt);

	md = lnet_handle2md(&mdh);
	if (!md) {
	lnet_res_unlock(cpt);
	return -ENOENT;
	}

	md->md_flags \|= LNET_MD_FLAG_ABORTED;
	/*
	* If the MD is busy, lnet_md_unlink just marks it for deletion, and
	* when the LND is done, the completion event flags that the MD was
	* unlinked. Otherwise, we enqueue an event now...
	*/
	if (md->md_eq && !md->md_refcount) {
	lnet_build_unlink_event(md, &ev);
	lnet_eq_enqueue_event(md->md_eq, &ev);
	}

	lnet_md_unlink(md);

	lnet_res_unlock(cpt);
	return 0;
	}
	EXPORT_SYMBOL(LNetMDUnlink);