path: root/drivers/staging/lustre/lustre/osc/osc_lock.c

/*
 * 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) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Implementation of cl_lock for OSC layer.
 *
 *   Author: Nikita Danilov <nikita.danilov@sun.com>
 *   Author: Jinshan Xiong <jinshan.xiong@intel.com>
 */

#define DEBUG_SUBSYSTEM S_OSC

#include "../../include/linux/libcfs/libcfs.h"
/* fid_build_reg_res_name() */
#include "../include/lustre_fid.h"

#include "osc_cl_internal.h"

/** \addtogroup osc
 *  @{
 */

/*****************************************************************************
 *
 * Type conversions.
 *
 */

static const struct cl_lock_operations osc_lock_ops;
static const struct cl_lock_operations osc_lock_lockless_ops;
static void osc_lock_to_lockless(const struct lu_env *env,
				 struct osc_lock *ols, int force);

int osc_lock_is_lockless(const struct osc_lock *olck)
{
	return (olck->ols_cl.cls_ops == &osc_lock_lockless_ops);
}

/**
 * Returns a weak pointer to the ldlm lock identified by a handle. Returned
 * pointer cannot be dereferenced, as lock is not protected from concurrent
 * reclaim. This function is a helper for osc_lock_invariant().
 */
static struct ldlm_lock *osc_handle_ptr(struct lustre_handle *handle)
{
	struct ldlm_lock *lock;

	lock = ldlm_handle2lock(handle);
	if (lock)
		LDLM_LOCK_PUT(lock);
	return lock;
}

/**
 * Invariant that has to be true all of the time.
 */
static int osc_lock_invariant(struct osc_lock *ols)
{
	struct ldlm_lock *lock = osc_handle_ptr(&ols->ols_handle);
	struct ldlm_lock *olock = ols->ols_dlmlock;
	int handle_used = lustre_handle_is_used(&ols->ols_handle);

	if (ergo(osc_lock_is_lockless(ols),
		 ols->ols_locklessable && !ols->ols_dlmlock))
		return 1;

	/*
	 * If all the following "ergo"s are true, return 1, otherwise 0
	 */
	if (!ergo(olock, handle_used))
		return 0;

	if (!ergo(olock, olock->l_handle.h_cookie == ols->ols_handle.cookie))
		return 0;

	if (!ergo(handle_used,
		  ergo(lock && olock, lock == olock) &&
		  ergo(!lock, !olock)))
		return 0;
	/*
	 * Check that ->ols_handle and ->ols_dlmlock are consistent, but
	 * take into account that they are set at the different time.
	 */
	if (!ergo(ols->ols_state == OLS_CANCELLED,
		  !olock && !handle_used))
		return 0;
	/*
	 * DLM lock is destroyed only after we have seen cancellation
	 * ast.
	 */
	if (!ergo(olock && ols->ols_state < OLS_CANCELLED,
		  !ldlm_is_destroyed(olock)))
		return 0;

	if (!ergo(ols->ols_state == OLS_GRANTED,
		  olock && olock->l_req_mode == olock->l_granted_mode &&
		  ols->ols_hold))
		return 0;
	return 1;
}

/*****************************************************************************
 *
 * Lock operations.
 *
 */

static void osc_lock_fini(const struct lu_env *env,
			  struct cl_lock_slice *slice)
{
	struct osc_lock *ols = cl2osc_lock(slice);

	LINVRNT(osc_lock_invariant(ols));
	LASSERT(!ols->ols_dlmlock);

	kmem_cache_free(osc_lock_kmem, ols);
}

static void osc_lock_build_policy(const struct lu_env *env,
				  const struct cl_lock *lock,
				  ldlm_policy_data_t *policy)
{
	const struct cl_lock_descr *d = &lock->cll_descr;

	osc_index2policy(policy, d->cld_obj, d->cld_start, d->cld_end);
	policy->l_extent.gid = d->cld_gid;
}

static __u64 osc_enq2ldlm_flags(__u32 enqflags)
{
	__u64 result = 0;

	LASSERT((enqflags & ~CEF_MASK) == 0);

	if (enqflags & CEF_NONBLOCK)
		result |= LDLM_FL_BLOCK_NOWAIT;
	if (enqflags & CEF_ASYNC)
		result |= LDLM_FL_HAS_INTENT;
	if (enqflags & CEF_DISCARD_DATA)
		result |= LDLM_FL_AST_DISCARD_DATA;
	if (enqflags & CEF_PEEK)
		result |= LDLM_FL_TEST_LOCK;
	return result;
}

/**
 * Updates object attributes from a lock value block (lvb) received together
 * with the DLM lock reply from the server. Copy of osc_update_enqueue()
 * logic.
 *
 * This can be optimized to not update attributes when lock is a result of a
 * local match.
 *
 * Called under lock and resource spin-locks.
 */
static void osc_lock_lvb_update(const struct lu_env *env,
				struct osc_object *osc,
				struct ldlm_lock *dlmlock,
				struct ost_lvb *lvb)
{
	struct cl_object *obj = osc2cl(osc);
	struct lov_oinfo *oinfo = osc->oo_oinfo;
	struct cl_attr *attr = &osc_env_info(env)->oti_attr;
	unsigned valid;

	valid = CAT_BLOCKS | CAT_ATIME | CAT_CTIME | CAT_MTIME | CAT_SIZE;
	if (!lvb)
		lvb = dlmlock->l_lvb_data;

	cl_lvb2attr(attr, lvb);

	cl_object_attr_lock(obj);
	if (dlmlock) {
		__u64 size;

		check_res_locked(dlmlock->l_resource);
		LASSERT(lvb == dlmlock->l_lvb_data);
		size = lvb->lvb_size;

		/* Extend KMS up to the end of this lock and no further
		 * A lock on [x,y] means a KMS of up to y + 1 bytes!
		 */
		if (size > dlmlock->l_policy_data.l_extent.end)
			size = dlmlock->l_policy_data.l_extent.end + 1;
		if (size >= oinfo->loi_kms) {
			LDLM_DEBUG(dlmlock, "lock acquired, setting rss=%llu, kms=%llu",
				   lvb->lvb_size, size);
			valid |= CAT_KMS;
			attr->cat_kms = size;
		} else {
			LDLM_DEBUG(dlmlock, "lock acquired, setting rss=%llu; leaving kms=%llu, end=%llu",
				   lvb->lvb_size, oinfo->loi_kms,
				   dlmlock->l_policy_data.l_extent.end);
		}
		ldlm_lock_allow_match_locked(dlmlock);
	}

	cl_object_attr_update(env, obj, attr, valid);
	cl_object_attr_unlock(obj);
}

static void osc_lock_granted(const struct lu_env *env, struct osc_lock *oscl,
			     struct lustre_handle *lockh, bool lvb_update)
{
	struct ldlm_lock *dlmlock;

	dlmlock = ldlm_handle2lock_long(lockh, 0);
	LASSERT(dlmlock);

	/* lock reference taken by ldlm_handle2lock_long() is
	 * owned by osc_lock and released in osc_lock_detach()
	 */
	lu_ref_add(&dlmlock->l_reference, "osc_lock", oscl);
	oscl->ols_has_ref = 1;

	LASSERT(!oscl->ols_dlmlock);
	oscl->ols_dlmlock = dlmlock;

	/* This may be a matched lock for glimpse request, do not hold
	 * lock reference in that case.
	 */
	if (!oscl->ols_glimpse) {
		/* hold a refc for non glimpse lock which will
		 * be released in osc_lock_cancel()
		 */
		lustre_handle_copy(&oscl->ols_handle, lockh);
		ldlm_lock_addref(lockh, oscl->ols_einfo.ei_mode);
		oscl->ols_hold = 1;
	}

	/* Lock must have been granted. */
	lock_res_and_lock(dlmlock);
	if (dlmlock->l_granted_mode == dlmlock->l_req_mode) {
		struct ldlm_extent *ext = &dlmlock->l_policy_data.l_extent;
		struct cl_lock_descr *descr = &oscl->ols_cl.cls_lock->cll_descr;

		/* extend the lock extent, otherwise it will have problem when
		 * we decide whether to grant a lockless lock.
		 */
		descr->cld_mode = osc_ldlm2cl_lock(dlmlock->l_granted_mode);
		descr->cld_start = cl_index(descr->cld_obj, ext->start);
		descr->cld_end = cl_index(descr->cld_obj, ext->end);
		descr->cld_gid = ext->gid;

		/* no lvb update for matched lock */
		if (lvb_update) {
			LASSERT(oscl->ols_flags & LDLM_FL_LVB_READY);
			osc_lock_lvb_update(env, cl2osc(oscl->ols_cl.cls_obj),
					    dlmlock, NULL);
		}
		LINVRNT(osc_lock_invariant(oscl));
	}
	unlock_res_and_lock(dlmlock);

	LASSERT(oscl->ols_state != OLS_GRANTED);
	oscl->ols_state = OLS_GRANTED;
}

/**
 * Lock upcall function that is executed either when a reply to ENQUEUE rpc is
 * received from a server, or after osc_enqueue_base() matched a local DLM
 * lock.
 */
static int osc_lock_upcall(void *cookie, struct lustre_handle *lockh,
			   int errcode)
{
	struct osc_lock *oscl = cookie;
	struct cl_lock_slice *slice = &oscl->ols_cl;
	struct lu_env *env;
	struct cl_env_nest nest;
	int rc;

	env = cl_env_nested_get(&nest);
	/* should never happen, similar to osc_ldlm_blocking_ast(). */
	LASSERT(!IS_ERR(env));

	rc = ldlm_error2errno(errcode);
	if (oscl->ols_state == OLS_ENQUEUED) {
		oscl->ols_state = OLS_UPCALL_RECEIVED;
	} else if (oscl->ols_state == OLS_CANCELLED) {
		rc = -EIO;
	} else {
		CERROR("Impossible state: %d\n", oscl->ols_state);
		LBUG();
	}

	if (rc == 0)
		osc_lock_granted(env, oscl, lockh, errcode == ELDLM_OK);

	/* Error handling, some errors are tolerable. */
	if (oscl->ols_locklessable && rc == -EUSERS) {
		/* This is a tolerable error, turn this lock into
		 * lockless lock.
		 */
		osc_object_set_contended(cl2osc(slice->cls_obj));
		LASSERT(slice->cls_ops == &osc_lock_ops);

		/* Change this lock to ldlmlock-less lock. */
		osc_lock_to_lockless(env, oscl, 1);
		oscl->ols_state = OLS_GRANTED;
		rc = 0;
	} else if (oscl->ols_glimpse && rc == -ENAVAIL) {
		LASSERT(oscl->ols_flags & LDLM_FL_LVB_READY);
		osc_lock_lvb_update(env, cl2osc(slice->cls_obj),
				    NULL, &oscl->ols_lvb);
		/* Hide the error. */
		rc = 0;
	}

	if (oscl->ols_owner)
		cl_sync_io_note(env, oscl->ols_owner, rc);
	cl_env_nested_put(&nest, env);

	return rc;
}

static int osc_lock_upcall_agl(void *cookie, struct lustre_handle *lockh,
			       int errcode)
{
	struct osc_object *osc = cookie;
	struct ldlm_lock *dlmlock;
	struct lu_env *env;
	struct cl_env_nest nest;

	env = cl_env_nested_get(&nest);
	LASSERT(!IS_ERR(env));

	if (errcode == ELDLM_LOCK_MATCHED) {
		errcode = ELDLM_OK;
		goto out;
	}

	if (errcode != ELDLM_OK)
		goto out;

	dlmlock = ldlm_handle2lock(lockh);
	LASSERT(dlmlock);

	lock_res_and_lock(dlmlock);
	LASSERT(dlmlock->l_granted_mode == dlmlock->l_req_mode);

	/* there is no osc_lock associated with AGL lock */
	osc_lock_lvb_update(env, osc, dlmlock, NULL);

	unlock_res_and_lock(dlmlock);
	LDLM_LOCK_PUT(dlmlock);

out:
	cl_object_put(env, osc2cl(osc));
	cl_env_nested_put(&nest, env);
	return ldlm_error2errno(errcode);
}

static int osc_lock_flush(struct osc_object *obj, pgoff_t start, pgoff_t end,
			  enum cl_lock_mode mode, int discard)
{
	struct lu_env *env;
	struct cl_env_nest nest;
	int rc = 0;
	int rc2 = 0;

	env = cl_env_nested_get(&nest);
	if (IS_ERR(env))
		return PTR_ERR(env);

	if (mode == CLM_WRITE) {
		rc = osc_cache_writeback_range(env, obj, start, end, 1,
					       discard);
		CDEBUG(D_CACHE, "object %p: [%lu -> %lu] %d pages were %s.\n",
		       obj, start, end, rc,
		       discard ? "discarded" : "written back");
		if (rc > 0)
			rc = 0;
	}

	rc2 = osc_lock_discard_pages(env, obj, start, end, mode);
	if (rc == 0 && rc2 < 0)
		rc = rc2;

	cl_env_nested_put(&nest, env);
	return rc;
}

/**
 * Helper for osc_dlm_blocking_ast() handling discrepancies between cl_lock
 * and ldlm_lock caches.
 */
static int osc_dlm_blocking_ast0(const struct lu_env *env,
				 struct ldlm_lock *dlmlock,
				 void *data, int flag)
{
	struct cl_object *obj = NULL;
	int result = 0;
	int discard;
	enum cl_lock_mode mode = CLM_READ;

	LASSERT(flag == LDLM_CB_CANCELING);

	lock_res_and_lock(dlmlock);
	if (dlmlock->l_granted_mode != dlmlock->l_req_mode) {
		dlmlock->l_ast_data = NULL;
		unlock_res_and_lock(dlmlock);
		return 0;
	}

	discard = ldlm_is_discard_data(dlmlock);
	if (dlmlock->l_granted_mode & (LCK_PW | LCK_GROUP))
		mode = CLM_WRITE;

	if (dlmlock->l_ast_data) {
		obj = osc2cl(dlmlock->l_ast_data);
		dlmlock->l_ast_data = NULL;

		cl_object_get(obj);
	}

	unlock_res_and_lock(dlmlock);

	/* if l_ast_data is NULL, the dlmlock was enqueued by AGL or
	 * the object has been destroyed.
	 */
	if (obj) {
		struct ldlm_extent *extent = &dlmlock->l_policy_data.l_extent;
		struct cl_attr *attr = &osc_env_info(env)->oti_attr;
		__u64 old_kms;

		/* Destroy pages covered by the extent of the DLM lock */
		result = osc_lock_flush(cl2osc(obj),
					cl_index(obj, extent->start),
					cl_index(obj, extent->end),
					mode, discard);

		/* losing a lock, update kms */
		lock_res_and_lock(dlmlock);
		cl_object_attr_lock(obj);
		/* Must get the value under the lock to avoid race. */
		old_kms = cl2osc(obj)->oo_oinfo->loi_kms;
		/* Update the kms. Need to loop all granted locks.
		 * Not a problem for the client
		 */
		attr->cat_kms = ldlm_extent_shift_kms(dlmlock, old_kms);

		cl_object_attr_update(env, obj, attr, CAT_KMS);
		cl_object_attr_unlock(obj);
		unlock_res_and_lock(dlmlock);

		cl_object_put(env, obj);
	}
	return result;
}

/**
 * Blocking ast invoked by ldlm when dlm lock is either blocking progress of
 * some other lock, or is canceled. This function is installed as a
 * ldlm_lock::l_blocking_ast() for client extent locks.
 *
 * Control flow is tricky, because ldlm uses the same call-back
 * (ldlm_lock::l_blocking_ast()) for both blocking and cancellation ast's.
 *
 * \param dlmlock lock for which ast occurred.
 *
 * \param new description of a conflicting lock in case of blocking ast.
 *
 * \param data value of dlmlock->l_ast_data
 *
 * \param flag LDLM_CB_BLOCKING or LDLM_CB_CANCELING. Used to distinguish
 *	     cancellation and blocking ast's.
 *
 * Possible use cases:
 *
 *     - ldlm calls dlmlock->l_blocking_ast(..., LDLM_CB_CANCELING) to cancel
 *       lock due to lock lru pressure, or explicit user request to purge
 *       locks.
 *
 *     - ldlm calls dlmlock->l_blocking_ast(..., LDLM_CB_BLOCKING) to notify
 *       us that dlmlock conflicts with another lock that some client is
 *       enqueing. Lock is canceled.
 *
 *	   - cl_lock_cancel() is called. osc_lock_cancel() calls
 *	     ldlm_cli_cancel() that calls
 *
 *		  dlmlock->l_blocking_ast(..., LDLM_CB_CANCELING)
 *
 *	     recursively entering osc_ldlm_blocking_ast().
 *
 *     - client cancels lock voluntary (e.g., as a part of early cancellation):
 *
 *	   cl_lock_cancel()->
 *	     osc_lock_cancel()->
 *	       ldlm_cli_cancel()->
 *		 dlmlock->l_blocking_ast(..., LDLM_CB_CANCELING)
 *
 */
static int osc_ldlm_blocking_ast(struct ldlm_lock *dlmlock,
				 struct ldlm_lock_desc *new, void *data,
				 int flag)
{
	int result = 0;

	switch (flag) {
	case LDLM_CB_BLOCKING: {
		struct lustre_handle lockh;

		ldlm_lock2handle(dlmlock, &lockh);
		result = ldlm_cli_cancel(&lockh, LCF_ASYNC);
		if (result == -ENODATA)
			result = 0;
		break;
	}
	case LDLM_CB_CANCELING: {
		struct lu_env *env;
		struct cl_env_nest nest;

		/*
		 * This can be called in the context of outer IO, e.g.,
		 *
		 *     osc_enqueue_base()->...
		 *	 ->ldlm_prep_elc_req()->...
		 *	   ->ldlm_cancel_callback()->...
		 *	     ->osc_ldlm_blocking_ast()
		 *
		 * new environment has to be created to not corrupt outer
		 * context.
		 */
		env = cl_env_nested_get(&nest);
		if (IS_ERR(env)) {
			result = PTR_ERR(env);
			break;
		}

		result = osc_dlm_blocking_ast0(env, dlmlock, data, flag);
		cl_env_nested_put(&nest, env);
		break;
		}
	default:
		LBUG();
	}
	return result;
}

static int osc_ldlm_glimpse_ast(struct ldlm_lock *dlmlock, void *data)
{
	struct ptlrpc_request *req = data;
	struct cl_env_nest nest;
	struct lu_env *env;
	struct ost_lvb *lvb;
	struct req_capsule *cap;
	int result;

	LASSERT(lustre_msg_get_opc(req->rq_reqmsg) == LDLM_GL_CALLBACK);

	env = cl_env_nested_get(&nest);
	if (!IS_ERR(env)) {
		struct cl_object *obj = NULL;

		lock_res_and_lock(dlmlock);
		if (dlmlock->l_ast_data) {
			obj = osc2cl(dlmlock->l_ast_data);
			cl_object_get(obj);
		}
		unlock_res_and_lock(dlmlock);

		if (obj) {
			/* Do not grab the mutex of cl_lock for glimpse.
			 * See LU-1274 for details.
			 * BTW, it's okay for cl_lock to be cancelled during
			 * this period because server can handle this race.
			 * See ldlm_server_glimpse_ast() for details.
			 * cl_lock_mutex_get(env, lock);
			 */
			cap = &req->rq_pill;
			req_capsule_extend(cap, &RQF_LDLM_GL_CALLBACK);
			req_capsule_set_size(cap, &RMF_DLM_LVB, RCL_SERVER,
					     sizeof(*lvb));
			result = req_capsule_server_pack(cap);
			if (result == 0) {
				lvb = req_capsule_server_get(cap, &RMF_DLM_LVB);
				result = cl_object_glimpse(env, obj, lvb);
			}
			if (!exp_connect_lvb_type(req->rq_export))
				req_capsule_shrink(&req->rq_pill,
						   &RMF_DLM_LVB,
						   sizeof(struct ost_lvb_v1),
						   RCL_SERVER);
			cl_object_put(env, obj);
		} else {
			/*
			 * These errors are normal races, so we don't want to
			 * fill the console with messages by calling
			 * ptlrpc_error()
			 */
			lustre_pack_reply(req, 1, NULL, NULL);
			result = -ELDLM_NO_LOCK_DATA;
		}
		cl_env_nested_put(&nest, env);
	} else {
		result = PTR_ERR(env);
	}
	req->rq_status = result;
	return result;
}

static int weigh_cb(const struct lu_env *env, struct cl_io *io,
		    struct osc_page *ops, void *cbdata)
{
	struct cl_page *page = ops->ops_cl.cpl_page;

	if (cl_page_is_vmlocked(env, page) ||
	    PageDirty(page->cp_vmpage) || PageWriteback(page->cp_vmpage)
	   )
		return CLP_GANG_ABORT;

	*(pgoff_t *)cbdata = osc_index(ops) + 1;
	return CLP_GANG_OKAY;
}

static unsigned long osc_lock_weight(const struct lu_env *env,
				     struct osc_object *oscobj,
				     struct ldlm_extent *extent)
{
	struct cl_io *io = &osc_env_info(env)->oti_io;
	struct cl_object *obj = cl_object_top(&oscobj->oo_cl);
	pgoff_t page_index;
	int result;

	io->ci_obj = obj;
	io->ci_ignore_layout = 1;
	result = cl_io_init(env, io, CIT_MISC, io->ci_obj);
	if (result != 0)
		return result;

	page_index = cl_index(obj, extent->start);
	do {
		result = osc_page_gang_lookup(env, io, oscobj,
					      page_index,
					      cl_index(obj, extent->end),
					      weigh_cb, (void *)&page_index);
		if (result == CLP_GANG_ABORT)
			break;
		if (result == CLP_GANG_RESCHED)
			cond_resched();
	} while (result != CLP_GANG_OKAY);
	cl_io_fini(env, io);

	return result == CLP_GANG_ABORT ? 1 : 0;
}

/**
 * Get the weight of dlm lock for early cancellation.
 */
unsigned long osc_ldlm_weigh_ast(struct ldlm_lock *dlmlock)
{
	struct cl_env_nest       nest;
	struct lu_env           *env;
	struct osc_object	*obj;
	struct osc_lock		*oscl;
	unsigned long            weight;
	bool			 found = false;

	might_sleep();
	/*
	 * osc_ldlm_weigh_ast has a complex context since it might be called
	 * because of lock canceling, or from user's input. We have to make
	 * a new environment for it. Probably it is implementation safe to use
	 * the upper context because cl_lock_put don't modify environment
	 * variables. But just in case ..
	 */
	env = cl_env_nested_get(&nest);
	if (IS_ERR(env))
		/* Mostly because lack of memory, do not eliminate this lock */
		return 1;

	LASSERT(dlmlock->l_resource->lr_type == LDLM_EXTENT);
	obj = dlmlock->l_ast_data;
	if (!obj) {
		weight = 1;
		goto out;
	}

	spin_lock(&obj->oo_ol_spin);
	list_for_each_entry(oscl, &obj->oo_ol_list, ols_nextlock_oscobj) {
		if (oscl->ols_dlmlock && oscl->ols_dlmlock != dlmlock)
			continue;
		found = true;
	}
	spin_unlock(&obj->oo_ol_spin);
	if (found) {
		/*
		 * If the lock is being used by an IO, definitely not cancel it.
		 */
		weight = 1;
		goto out;
	}

	weight = osc_lock_weight(env, obj, &dlmlock->l_policy_data.l_extent);

out:
	cl_env_nested_put(&nest, env);
	return weight;
}

static void osc_lock_build_einfo(const struct lu_env *env,
				 const struct cl_lock *lock,
				 struct osc_object *osc,
				 struct ldlm_enqueue_info *einfo)
{
	einfo->ei_type = LDLM_EXTENT;
	einfo->ei_mode   = osc_cl_lock2ldlm(lock->cll_descr.cld_mode);
	einfo->ei_cb_bl = osc_ldlm_blocking_ast;
	einfo->ei_cb_cp  = ldlm_completion_ast;
	einfo->ei_cb_gl = osc_ldlm_glimpse_ast;
	einfo->ei_cbdata = osc; /* value to be put into ->l_ast_data */
}

/**
 * Determine if the lock should be converted into a lockless lock.
 *
 * Steps to check:
 * - if the lock has an explicit requirement for a non-lockless lock;
 * - if the io lock request type ci_lockreq;
 * - send the enqueue rpc to ost to make the further decision;
 * - special treat to truncate lockless lock
 *
 *  Additional policy can be implemented here, e.g., never do lockless-io
 *  for large extents.
 */
static void osc_lock_to_lockless(const struct lu_env *env,
				 struct osc_lock *ols, int force)
{
	struct cl_lock_slice *slice = &ols->ols_cl;

	LASSERT(ols->ols_state == OLS_NEW ||
		ols->ols_state == OLS_UPCALL_RECEIVED);

	if (force) {
		ols->ols_locklessable = 1;
		slice->cls_ops = &osc_lock_lockless_ops;
	} else {
		struct osc_io *oio = osc_env_io(env);
		struct cl_io *io = oio->oi_cl.cis_io;
		struct cl_object *obj = slice->cls_obj;
		struct osc_object *oob = cl2osc(obj);
		const struct osc_device *osd = lu2osc_dev(obj->co_lu.lo_dev);
		struct obd_connect_data *ocd;

		LASSERT(io->ci_lockreq == CILR_MANDATORY ||
			io->ci_lockreq == CILR_MAYBE ||
			io->ci_lockreq == CILR_NEVER);

		ocd = &class_exp2cliimp(osc_export(oob))->imp_connect_data;
		ols->ols_locklessable = (io->ci_type != CIT_SETATTR) &&
				(io->ci_lockreq == CILR_MAYBE) &&
				(ocd->ocd_connect_flags & OBD_CONNECT_SRVLOCK);
		if (io->ci_lockreq == CILR_NEVER ||
			/* lockless IO */
		    (ols->ols_locklessable && osc_object_is_contended(oob)) ||
			/* lockless truncate */
		    (cl_io_is_trunc(io) &&
		     (ocd->ocd_connect_flags & OBD_CONNECT_TRUNCLOCK) &&
		      osd->od_lockless_truncate)) {
			ols->ols_locklessable = 1;
			slice->cls_ops = &osc_lock_lockless_ops;
		}
	}
	LASSERT(ergo(ols->ols_glimpse, !osc_lock_is_lockless(ols)));
}

static bool osc_lock_compatible(const struct osc_lock *qing,
				const struct osc_lock *qed)
{
	struct cl_lock_descr *qed_descr = &qed->ols_cl.cls_lock->cll_descr;
	struct cl_lock_descr *qing_descr = &qing->ols_cl.cls_lock->cll_descr;

	if (qed->ols_glimpse)
		return true;

	if (qing_descr->cld_mode == CLM_READ && qed_descr->cld_mode == CLM_READ)
		return true;

	if (qed->ols_state < OLS_GRANTED)
		return true;

	if (qed_descr->cld_mode  >= qing_descr->cld_mode &&
	    qed_descr->cld_start <= qing_descr->cld_start &&
	    qed_descr->cld_end   >= qing_descr->cld_end)
		return true;

	return false;
}

static void osc_lock_wake_waiters(const struct lu_env *env,
				  struct osc_object *osc,
				  struct osc_lock *oscl)
{
	spin_lock(&osc->oo_ol_spin);
	list_del_init(&oscl->ols_nextlock_oscobj);
	spin_unlock(&osc->oo_ol_spin);

	spin_lock(&oscl->ols_lock);
	while (!list_empty(&oscl->ols_waiting_list)) {
		struct osc_lock *scan;

		scan = list_entry(oscl->ols_waiting_list.next, struct osc_lock,
				  ols_wait_entry);
		list_del_init(&scan->ols_wait_entry);

		cl_sync_io_note(env, scan->ols_owner, 0);
	}
	spin_unlock(&oscl->ols_lock);
}

static void osc_lock_enqueue_wait(const struct lu_env *env,
				  struct osc_object *obj,
				  struct osc_lock *oscl)
{
	struct osc_lock *tmp_oscl;
	struct cl_lock_descr *need = &oscl->ols_cl.cls_lock->cll_descr;
	struct cl_sync_io *waiter = &osc_env_info(env)->oti_anchor;

	spin_lock(&obj->oo_ol_spin);
	list_add_tail(&oscl->ols_nextlock_oscobj, &obj->oo_ol_list);

restart:
	list_for_each_entry(tmp_oscl, &obj->oo_ol_list,
			    ols_nextlock_oscobj) {
		struct cl_lock_descr *descr;

		if (tmp_oscl == oscl)
			break;

		descr = &tmp_oscl->ols_cl.cls_lock->cll_descr;
		if (descr->cld_start > need->cld_end ||
		    descr->cld_end   < need->cld_start)
			continue;

		/* We're not supposed to give up group lock */
		if (descr->cld_mode == CLM_GROUP)
			break;

		if (!osc_lock_is_lockless(oscl) &&
		    osc_lock_compatible(oscl, tmp_oscl))
			continue;

		/* wait for conflicting lock to be canceled */
		cl_sync_io_init(waiter, 1, cl_sync_io_end);
		oscl->ols_owner = waiter;

		spin_lock(&tmp_oscl->ols_lock);
		/* add oscl into tmp's ols_waiting list */
		list_add_tail(&oscl->ols_wait_entry,
			      &tmp_oscl->ols_waiting_list);
		spin_unlock(&tmp_oscl->ols_lock);

		spin_unlock(&obj->oo_ol_spin);
		(void)cl_sync_io_wait(env, waiter, 0);

		spin_lock(&obj->oo_ol_spin);
		oscl->ols_owner = NULL;
		goto restart;
	}
	spin_unlock(&obj->oo_ol_spin);
}

/**
 * Implementation of cl_lock_operations::clo_enqueue() method for osc
 * layer. This initiates ldlm enqueue:
 *
 *     - cancels conflicting locks early (osc_lock_enqueue_wait());
 *
 *     - calls osc_enqueue_base() to do actual enqueue.
 *
 * osc_enqueue_base() is supplied with an upcall function that is executed
 * when lock is received either after a local cached ldlm lock is matched, or
 * when a reply from the server is received.
 *
 * This function does not wait for the network communication to complete.
 */
static int osc_lock_enqueue(const struct lu_env *env,
			    const struct cl_lock_slice *slice,
			    struct cl_io *unused, struct cl_sync_io *anchor)
{
	struct osc_thread_info *info = osc_env_info(env);
	struct osc_io *oio = osc_env_io(env);
	struct osc_object *osc = cl2osc(slice->cls_obj);
	struct osc_lock *oscl = cl2osc_lock(slice);
	struct cl_lock *lock = slice->cls_lock;
	struct ldlm_res_id *resname = &info->oti_resname;
	ldlm_policy_data_t *policy = &info->oti_policy;
	osc_enqueue_upcall_f upcall = osc_lock_upcall;
	void *cookie = oscl;
	bool async = false;
	int result;

	LASSERTF(ergo(oscl->ols_glimpse, lock->cll_descr.cld_mode <= CLM_READ),
		 "lock = %p, ols = %p\n", lock, oscl);

	if (oscl->ols_state == OLS_GRANTED)
		return 0;

	if (oscl->ols_flags & LDLM_FL_TEST_LOCK)
		goto enqueue_base;

	if (oscl->ols_glimpse) {
		LASSERT(equi(oscl->ols_agl, !anchor));
		async = true;
		goto enqueue_base;
	}

	osc_lock_enqueue_wait(env, osc, oscl);

	/* we can grant lockless lock right after all conflicting locks
	 * are canceled.
	 */
	if (osc_lock_is_lockless(oscl)) {
		oscl->ols_state = OLS_GRANTED;
		oio->oi_lockless = 1;
		return 0;
	}

enqueue_base:
	oscl->ols_state = OLS_ENQUEUED;
	if (anchor) {
		atomic_inc(&anchor->csi_sync_nr);
		oscl->ols_owner = anchor;
	}

	/**
	 * DLM lock's ast data must be osc_object;
	 * if glimpse or AGL lock, async of osc_enqueue_base() must be true,
	 * DLM's enqueue callback set to osc_lock_upcall() with cookie as
	 * osc_lock.
	 */
	ostid_build_res_name(&osc->oo_oinfo->loi_oi, resname);
	osc_lock_build_einfo(env, lock, osc, &oscl->ols_einfo);
	osc_lock_build_policy(env, lock, policy);
	if (oscl->ols_agl) {
		oscl->ols_einfo.ei_cbdata = NULL;
		/* hold a reference for callback */
		cl_object_get(osc2cl(osc));
		upcall = osc_lock_upcall_agl;
		cookie = osc;
	}
	result = osc_enqueue_base(osc_export(osc), resname, &oscl->ols_flags,
				  policy, &oscl->ols_lvb,
				  osc->oo_oinfo->loi_kms_valid,
				  upcall, cookie,
				  &oscl->ols_einfo, PTLRPCD_SET, async,
				  oscl->ols_agl);
	if (result != 0) {
		oscl->ols_state = OLS_CANCELLED;
		osc_lock_wake_waiters(env, osc, oscl);

		/* hide error for AGL lock. */
		if (oscl->ols_agl) {
			cl_object_put(env, osc2cl(osc));
			result = 0;
		}
		if (anchor)
			cl_sync_io_note(env, anchor, result);
	} else {
		if (osc_lock_is_lockless(oscl)) {
			oio->oi_lockless = 1;
		} else if (!async) {
			LASSERT(oscl->ols_state == OLS_GRANTED);
			LASSERT(oscl->ols_hold);
			LASSERT(oscl->ols_dlmlock);
		}
	}
	return result;
}

/**
 * Breaks a link between osc_lock and dlm_lock.
 */
static void osc_lock_detach(const struct lu_env *env, struct osc_lock *olck)
{
	struct ldlm_lock *dlmlock;

	dlmlock = olck->ols_dlmlock;
	if (!dlmlock)
		return;

	if (olck->ols_hold) {
		olck->ols_hold = 0;
		osc_cancel_base(&olck->ols_handle, olck->ols_einfo.ei_mode);
		olck->ols_handle.cookie = 0ULL;
	}

	olck->ols_dlmlock = NULL;

	/* release a reference taken in osc_lock_upcall(). */
	LASSERT(olck->ols_has_ref);
	lu_ref_del(&dlmlock->l_reference, "osc_lock", olck);
	LDLM_LOCK_RELEASE(dlmlock);
	olck->ols_has_ref = 0;
}

/**
 * Implements cl_lock_operations::clo_cancel() method for osc layer. This is
 * called (as part of cl_lock_cancel()) when lock is canceled either voluntary
 * (LRU pressure, early cancellation, umount, etc.) or due to the conflict
 * with some other lock some where in the cluster. This function does the
 * following:
 *
 *     - invalidates all pages protected by this lock (after sending dirty
 *       ones to the server, as necessary);
 *
 *     - decref's underlying ldlm lock;
 *
 *     - cancels ldlm lock (ldlm_cli_cancel()).
 */
static void osc_lock_cancel(const struct lu_env *env,
			    const struct cl_lock_slice *slice)
{
	struct osc_object *obj  = cl2osc(slice->cls_obj);
	struct osc_lock *oscl = cl2osc_lock(slice);

	LINVRNT(osc_lock_invariant(oscl));

	osc_lock_detach(env, oscl);
	oscl->ols_state = OLS_CANCELLED;
	oscl->ols_flags &= ~LDLM_FL_LVB_READY;

	osc_lock_wake_waiters(env, obj, oscl);
}

static int osc_lock_print(const struct lu_env *env, void *cookie,
			  lu_printer_t p, const struct cl_lock_slice *slice)
{
	struct osc_lock *lock = cl2osc_lock(slice);

	(*p)(env, cookie, "%p %#16llx %#llx %d %p ",
	     lock->ols_dlmlock, lock->ols_flags, lock->ols_handle.cookie,
	     lock->ols_state, lock->ols_owner);
	osc_lvb_print(env, cookie, p, &lock->ols_lvb);
	return 0;
}

static const struct cl_lock_operations osc_lock_ops = {
	.clo_fini    = osc_lock_fini,
	.clo_enqueue = osc_lock_enqueue,
	.clo_cancel  = osc_lock_cancel,
	.clo_print   = osc_lock_print,
};

static void osc_lock_lockless_cancel(const struct lu_env *env,
				     const struct cl_lock_slice *slice)
{
	struct osc_lock *ols = cl2osc_lock(slice);
	struct osc_object *osc = cl2osc(slice->cls_obj);
	struct cl_lock_descr *descr = &slice->cls_lock->cll_descr;
	int result;

	LASSERT(!ols->ols_dlmlock);
	result = osc_lock_flush(osc, descr->cld_start, descr->cld_end,
				descr->cld_mode, 0);
	if (result)
		CERROR("Pages for lockless lock %p were not purged(%d)\n",
		       ols, result);

	osc_lock_wake_waiters(env, osc, ols);
}

static const struct cl_lock_operations osc_lock_lockless_ops = {
	.clo_fini	= osc_lock_fini,
	.clo_enqueue	= osc_lock_enqueue,
	.clo_cancel	= osc_lock_lockless_cancel,
	.clo_print	= osc_lock_print
};

static void osc_lock_set_writer(const struct lu_env *env,
				const struct cl_io *io,
				struct cl_object *obj, struct osc_lock *oscl)
{
	struct cl_lock_descr *descr = &oscl->ols_cl.cls_lock->cll_descr;
	pgoff_t io_start;
	pgoff_t io_end;

	if (!cl_object_same(io->ci_obj, obj))
		return;

	if (likely(io->ci_type == CIT_WRITE)) {
		io_start = cl_index(obj, io->u.ci_rw.crw_pos);
		io_end = cl_index(obj, io->u.ci_rw.crw_pos +
				  io->u.ci_rw.crw_count - 1);
		if (cl_io_is_append(io)) {
			io_start = 0;
			io_end = CL_PAGE_EOF;
		}
	} else {
		LASSERT(cl_io_is_mkwrite(io));
		io_start = io->u.ci_fault.ft_index;
		io_end = io->u.ci_fault.ft_index;
	}

	if (descr->cld_mode >= CLM_WRITE &&
	    descr->cld_start <= io_start && descr->cld_end >= io_end) {
		struct osc_io *oio = osc_env_io(env);

		/* There must be only one lock to match the write region */
		LASSERT(!oio->oi_write_osclock);
		oio->oi_write_osclock = oscl;
	}
}

int osc_lock_init(const struct lu_env *env,
		  struct cl_object *obj, struct cl_lock *lock,
		  const struct cl_io *io)
{
	struct osc_lock *oscl;
	__u32 enqflags = lock->cll_descr.cld_enq_flags;

	oscl = kmem_cache_zalloc(osc_lock_kmem, GFP_NOFS);
	if (!oscl)
		return -ENOMEM;

	oscl->ols_state = OLS_NEW;
	spin_lock_init(&oscl->ols_lock);
	INIT_LIST_HEAD(&oscl->ols_waiting_list);
	INIT_LIST_HEAD(&oscl->ols_wait_entry);
	INIT_LIST_HEAD(&oscl->ols_nextlock_oscobj);

	oscl->ols_flags = osc_enq2ldlm_flags(enqflags);
	oscl->ols_agl = !!(enqflags & CEF_AGL);
	if (oscl->ols_agl)
		oscl->ols_flags |= LDLM_FL_BLOCK_NOWAIT;
	if (oscl->ols_flags & LDLM_FL_HAS_INTENT) {
		oscl->ols_flags |= LDLM_FL_BLOCK_GRANTED;
		oscl->ols_glimpse = 1;
	}

	cl_lock_slice_add(lock, &oscl->ols_cl, obj, &osc_lock_ops);

	if (!(enqflags & CEF_MUST))
		/* try to convert this lock to a lockless lock */
		osc_lock_to_lockless(env, oscl, (enqflags & CEF_NEVER));
	if (oscl->ols_locklessable && !(enqflags & CEF_DISCARD_DATA))
		oscl->ols_flags |= LDLM_FL_DENY_ON_CONTENTION;

	if (io->ci_type == CIT_WRITE || cl_io_is_mkwrite(io))
		osc_lock_set_writer(env, io, obj, oscl);


	LDLM_DEBUG_NOLOCK("lock %p, osc lock %p, flags %llx",
			  lock, oscl, oscl->ols_flags);

	return 0;
}

/**
 * Finds an existing lock covering given index and optionally different from a
 * given \a except lock.
 */
struct ldlm_lock *osc_dlmlock_at_pgoff(const struct lu_env *env,
				       struct osc_object *obj, pgoff_t index,
				       int pending, int canceling)
{
	struct osc_thread_info *info = osc_env_info(env);
	struct ldlm_res_id *resname = &info->oti_resname;
	ldlm_policy_data_t *policy  = &info->oti_policy;
	struct lustre_handle lockh;
	struct ldlm_lock *lock = NULL;
	enum ldlm_mode mode;
	__u64 flags;

	ostid_build_res_name(&obj->oo_oinfo->loi_oi, resname);
	osc_index2policy(policy, osc2cl(obj), index, index);
	policy->l_extent.gid = LDLM_GID_ANY;

	flags = LDLM_FL_BLOCK_GRANTED | LDLM_FL_TEST_LOCK;
	if (pending)
		flags |= LDLM_FL_CBPENDING;
	/*
	 * It is fine to match any group lock since there could be only one
	 * with a uniq gid and it conflicts with all other lock modes too
	 */
again:
	mode = ldlm_lock_match(osc_export(obj)->exp_obd->obd_namespace,
			       flags, resname, LDLM_EXTENT, policy,
			       LCK_PR | LCK_PW | LCK_GROUP, &lockh, canceling);
	if (mode != 0) {
		lock = ldlm_handle2lock(&lockh);
		/* RACE: the lock is cancelled so let's try again */
		if (unlikely(!lock))
			goto again;
	}
	return lock;
}

/** @} osc */