staging: lustre: replace OBD_SLAB_FREE_PTR with kmem_cache_free

[mirror_ubuntu-artful-kernel.git] / 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.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, 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>
 */

#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
 *  @{
 */

#define _PAGEREF_MAGIC  (-10000000)

/*****************************************************************************
 *
 * 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);
static int osc_lock_has_pages(struct osc_lock *olck);

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 != NULL)
                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_lock;
        int handle_used = lustre_handle_is_used(&ols->ols_handle);

        if (ergo(osc_lock_is_lockless(ols),
                 ols->ols_locklessable && ols->ols_lock == NULL))
                return 1;

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

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

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

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

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

/**
 * 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;

        spin_lock(&osc_ast_guard);
        dlmlock = olck->ols_lock;
        if (dlmlock == NULL) {
                spin_unlock(&osc_ast_guard);
                return;
        }

        olck->ols_lock = NULL;
        /* wb(); --- for all who checks (ols->ols_lock != NULL) before
         * call to osc_lock_detach() */
        dlmlock->l_ast_data = NULL;
        olck->ols_handle.cookie = 0ULL;
        spin_unlock(&osc_ast_guard);

        lock_res_and_lock(dlmlock);
        if (dlmlock->l_granted_mode == dlmlock->l_req_mode) {
                struct cl_object *obj = olck->ols_cl.cls_obj;
                struct cl_attr *attr = &osc_env_info(env)->oti_attr;
                __u64 old_kms;

                cl_object_attr_lock(obj);
                /* Must get the value under the lock to avoid possible races. */
                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_set(env, obj, attr, CAT_KMS);
                cl_object_attr_unlock(obj);
        }
        unlock_res_and_lock(dlmlock);

        /* release a reference taken in osc_lock_upcall0(). */
        LASSERT(olck->ols_has_ref);
        lu_ref_del(&dlmlock->l_reference, "osc_lock", olck);
        LDLM_LOCK_RELEASE(dlmlock);
        olck->ols_has_ref = 0;
}

static int osc_lock_unhold(struct osc_lock *ols)
{
        int result = 0;

        if (ols->ols_hold) {
                ols->ols_hold = 0;
                result = osc_cancel_base(&ols->ols_handle,
                                         ols->ols_einfo.ei_mode);
        }
        return result;
}

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

        LINVRNT(osc_lock_invariant(ols));

        switch (ols->ols_state) {
        case OLS_NEW:
                LASSERT(!ols->ols_hold);
                LASSERT(ols->ols_agl);
                return 0;
        case OLS_UPCALL_RECEIVED:
                osc_lock_unhold(ols);
        case OLS_ENQUEUED:
                LASSERT(!ols->ols_hold);
                osc_lock_detach(env, ols);
                ols->ols_state = OLS_NEW;
                return 0;
        case OLS_GRANTED:
                LASSERT(!ols->ols_glimpse);
                LASSERT(ols->ols_hold);
                /*
                 * Move lock into OLS_RELEASED state before calling
                 * osc_cancel_base() so that possible synchronous cancellation
                 * (that always happens e.g., for liblustre) sees that lock is
                 * released.
                 */
                ols->ols_state = OLS_RELEASED;
                return osc_lock_unhold(ols);
        default:
                CERROR("Impossible state: %d\n", ols->ols_state);
                LBUG();
        }
}

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));
        /*
         * ->ols_hold can still be true at this point if, for example, a
         * thread that requested a lock was killed (and released a reference
         * to the lock), before reply from a server was received. In this case
         * lock is destroyed immediately after upcall.
         */
        osc_lock_unhold(ols);
        LASSERT(ols->ols_lock == NULL);
        LASSERT(atomic_read(&ols->ols_pageref) == 0 ||
                atomic_read(&ols->ols_pageref) == _PAGEREF_MAGIC);

        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;
        return result;
}

/**
 * Global spin-lock protecting consistency of ldlm_lock::l_ast_data
 * pointers. Initialized in osc_init().
 */
spinlock_t osc_ast_guard;

static struct osc_lock *osc_ast_data_get(struct ldlm_lock *dlm_lock)
{
        struct osc_lock *olck;

        lock_res_and_lock(dlm_lock);
        spin_lock(&osc_ast_guard);
        olck = dlm_lock->l_ast_data;
        if (olck != NULL) {
                struct cl_lock *lock = olck->ols_cl.cls_lock;
                /*
                 * If osc_lock holds a reference on ldlm lock, return it even
                 * when cl_lock is in CLS_FREEING state. This way
                 *
                 *       osc_ast_data_get(dlmlock) == NULL
                 *
                 * guarantees that all osc references on dlmlock were
                 * released. osc_dlm_blocking_ast0() relies on that.
                 */
                if (lock->cll_state < CLS_FREEING || olck->ols_has_ref) {
                        cl_lock_get_trust(lock);
                        lu_ref_add_atomic(&lock->cll_reference,
                                          "ast", current);
                } else
                        olck = NULL;
        }
        spin_unlock(&osc_ast_guard);
        unlock_res_and_lock(dlm_lock);
        return olck;
}

static void osc_ast_data_put(const struct lu_env *env, struct osc_lock *olck)
{
        struct cl_lock *lock;

        lock = olck->ols_cl.cls_lock;
        lu_ref_del(&lock->cll_reference, "ast", current);
        cl_lock_put(env, lock);
}

/**
 * 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_lock *olck,
                                int rc)
{
        struct ost_lvb *lvb;
        struct cl_object *obj;
        struct lov_oinfo *oinfo;
        struct cl_attr *attr;
        unsigned valid;

        if (!(olck->ols_flags & LDLM_FL_LVB_READY))
                return;

        lvb = &olck->ols_lvb;
        obj = olck->ols_cl.cls_obj;
        oinfo = cl2osc(obj)->oo_oinfo;
        attr = &osc_env_info(env)->oti_attr;
        valid = CAT_BLOCKS | CAT_ATIME | CAT_CTIME | CAT_MTIME | CAT_SIZE;
        cl_lvb2attr(attr, lvb);

        cl_object_attr_lock(obj);
        if (rc == 0) {
                struct ldlm_lock *dlmlock;
                __u64 size;

                dlmlock = olck->ols_lock;
                LASSERT(dlmlock != NULL);

                /* re-grab LVB from a dlm lock under DLM spin-locks. */
                *lvb = *(struct ost_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);
        } else if (rc == -ENAVAIL && olck->ols_glimpse) {
                CDEBUG(D_INODE, "glimpsed, setting rss=%llu; leaving kms=%llu\n",
                       lvb->lvb_size, oinfo->loi_kms);
        } else
                valid = 0;

        if (valid != 0)
                cl_object_attr_set(env, obj, attr, valid);

        cl_object_attr_unlock(obj);
}

/**
 * Called when a lock is granted, from an upcall (when server returned a
 * granted lock), or from completion AST, when server returned a blocked lock.
 *
 * Called under lock and resource spin-locks, that are released temporarily
 * here.
 */
static void osc_lock_granted(const struct lu_env *env, struct osc_lock *olck,
                             struct ldlm_lock *dlmlock, int rc)
{
        struct ldlm_extent *ext;
        struct cl_lock *lock;
        struct cl_lock_descr *descr;

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

        if (olck->ols_state < OLS_GRANTED) {
                lock = olck->ols_cl.cls_lock;
                ext = &dlmlock->l_policy_data.l_extent;
                descr = &osc_env_info(env)->oti_descr;
                descr->cld_obj = lock->cll_descr.cld_obj;

                /* XXX check that ->l_granted_mode is valid. */
                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;
                /*
                 * tell upper layers the extent of the lock that was actually
                 * granted
                 */
                olck->ols_state = OLS_GRANTED;
                osc_lock_lvb_update(env, olck, rc);

                /* release DLM spin-locks to allow cl_lock_{modify,signal}()
                 * to take a semaphore on a parent lock. This is safe, because
                 * spin-locks are needed to protect consistency of
                 * dlmlock->l_*_mode and LVB, and we have finished processing
                 * them. */
                unlock_res_and_lock(dlmlock);
                cl_lock_modify(env, lock, descr);
                cl_lock_signal(env, lock);
                LINVRNT(osc_lock_invariant(olck));
                lock_res_and_lock(dlmlock);
        }
}

static void osc_lock_upcall0(const struct lu_env *env, struct osc_lock *olck)

{
        struct ldlm_lock *dlmlock;

        dlmlock = ldlm_handle2lock_long(&olck->ols_handle, 0);
        LASSERT(dlmlock != NULL);

        lock_res_and_lock(dlmlock);
        spin_lock(&osc_ast_guard);
        LASSERT(dlmlock->l_ast_data == olck);
        LASSERT(olck->ols_lock == NULL);
        olck->ols_lock = dlmlock;
        spin_unlock(&osc_ast_guard);

        /*
         * Lock might be not yet granted. In this case, completion ast
         * (osc_ldlm_completion_ast()) comes later and finishes lock
         * granting.
         */
        if (dlmlock->l_granted_mode == dlmlock->l_req_mode)
                osc_lock_granted(env, olck, dlmlock, 0);
        unlock_res_and_lock(dlmlock);

        /*
         * osc_enqueue_interpret() decrefs asynchronous locks, counter
         * this.
         */
        ldlm_lock_addref(&olck->ols_handle, olck->ols_einfo.ei_mode);
        olck->ols_hold = 1;

        /* 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", olck);
        olck->ols_has_ref = 1;
}

/**
 * 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, int errcode)
{
        struct osc_lock *olck = cookie;
        struct cl_lock_slice *slice = &olck->ols_cl;
        struct cl_lock *lock = slice->cls_lock;
        struct lu_env *env;
        struct cl_env_nest nest;

        env = cl_env_nested_get(&nest);
        if (!IS_ERR(env)) {
                int rc;

                cl_lock_mutex_get(env, lock);

                LASSERT(lock->cll_state >= CLS_QUEUING);
                if (olck->ols_state == OLS_ENQUEUED) {
                        olck->ols_state = OLS_UPCALL_RECEIVED;
                        rc = ldlm_error2errno(errcode);
                } else if (olck->ols_state == OLS_CANCELLED) {
                        rc = -EIO;
                } else {
                        CERROR("Impossible state: %d\n", olck->ols_state);
                        LBUG();
                }
                if (rc) {
                        struct ldlm_lock *dlmlock;

                        dlmlock = ldlm_handle2lock(&olck->ols_handle);
                        if (dlmlock != NULL) {
                                lock_res_and_lock(dlmlock);
                                spin_lock(&osc_ast_guard);
                                LASSERT(olck->ols_lock == NULL);
                                dlmlock->l_ast_data = NULL;
                                olck->ols_handle.cookie = 0ULL;
                                spin_unlock(&osc_ast_guard);
                                ldlm_lock_fail_match_locked(dlmlock);
                                unlock_res_and_lock(dlmlock);
                                LDLM_LOCK_PUT(dlmlock);
                        }
                } else {
                        if (olck->ols_glimpse)
                                olck->ols_glimpse = 0;
                        osc_lock_upcall0(env, olck);
                }

                /* Error handling, some errors are tolerable. */
                if (olck->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, olck, 1);
                        olck->ols_state = OLS_GRANTED;
                        rc = 0;
                } else if (olck->ols_glimpse && rc == -ENAVAIL) {
                        osc_lock_lvb_update(env, olck, rc);
                        cl_lock_delete(env, lock);
                        /* Hide the error. */
                        rc = 0;
                }

                if (rc == 0) {
                        /* For AGL case, the RPC sponsor may exits the cl_lock
                        *  processing without wait() called before related OSC
                        *  lock upcall(). So update the lock status according
                        *  to the enqueue result inside AGL upcall(). */
                        if (olck->ols_agl) {
                                lock->cll_flags |= CLF_FROM_UPCALL;
                                cl_wait_try(env, lock);
                                lock->cll_flags &= ~CLF_FROM_UPCALL;
                                if (!olck->ols_glimpse)
                                        olck->ols_agl = 0;
                        }
                        cl_lock_signal(env, lock);
                        /* del user for lock upcall cookie */
                        cl_unuse_try(env, lock);
                } else {
                        /* del user for lock upcall cookie */
                        cl_lock_user_del(env, lock);
                        cl_lock_error(env, lock, rc);
                }

                /* release cookie reference, acquired by osc_lock_enqueue() */
                cl_lock_hold_release(env, lock, "upcall", lock);
                cl_lock_mutex_put(env, lock);

                lu_ref_del(&lock->cll_reference, "upcall", lock);
                /* This maybe the last reference, so must be called after
                 * cl_lock_mutex_put(). */
                cl_lock_put(env, lock);

                cl_env_nested_put(&nest, env);
        } else {
                /* should never happen, similar to osc_ldlm_blocking_ast(). */
                LBUG();
        }
        return errcode;
}

/**
 * Core of osc_dlm_blocking_ast() logic.
 */
static void osc_lock_blocking(const struct lu_env *env,
                              struct ldlm_lock *dlmlock,
                              struct osc_lock *olck, int blocking)
{
        struct cl_lock *lock = olck->ols_cl.cls_lock;

        LASSERT(olck->ols_lock == dlmlock);
        CLASSERT(OLS_BLOCKED < OLS_CANCELLED);
        LASSERT(!osc_lock_is_lockless(olck));

        /*
         * Lock might be still addref-ed here, if e.g., blocking ast
         * is sent for a failed lock.
         */
        osc_lock_unhold(olck);

        if (blocking && olck->ols_state < OLS_BLOCKED)
                /*
                 * Move osc_lock into OLS_BLOCKED before canceling the lock,
                 * because it recursively re-enters osc_lock_blocking(), with
                 * the state set to OLS_CANCELLED.
                 */
                olck->ols_state = OLS_BLOCKED;
        /*
         * cancel and destroy lock at least once no matter how blocking ast is
         * entered (see comment above osc_ldlm_blocking_ast() for use
         * cases). cl_lock_cancel() and cl_lock_delete() are idempotent.
         */
        cl_lock_cancel(env, lock);
        cl_lock_delete(env, lock);
}

/**
 * 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 osc_lock *olck;
        struct cl_lock *lock;
        int result;
        int cancel;

        LASSERT(flag == LDLM_CB_BLOCKING || flag == LDLM_CB_CANCELING);

        cancel = 0;
        olck = osc_ast_data_get(dlmlock);
        if (olck != NULL) {
                lock = olck->ols_cl.cls_lock;
                cl_lock_mutex_get(env, lock);
                LINVRNT(osc_lock_invariant(olck));
                if (olck->ols_ast_wait) {
                        /* wake up osc_lock_use() */
                        cl_lock_signal(env, lock);
                        olck->ols_ast_wait = 0;
                }
                /*
                 * Lock might have been canceled while this thread was
                 * sleeping for lock mutex, but olck is pinned in memory.
                 */
                if (olck == dlmlock->l_ast_data) {
                        /*
                         * NOTE: DLM sends blocking AST's for failed locks
                         *       (that are still in pre-OLS_GRANTED state)
                         *       too, and they have to be canceled otherwise
                         *       DLM lock is never destroyed and stuck in
                         *       the memory.
                         *
                         *       Alternatively, ldlm_cli_cancel() can be
                         *       called here directly for osc_locks with
                         *       ols_state < OLS_GRANTED to maintain an
                         *       invariant that ->clo_cancel() is only called
                         *       for locks that were granted.
                         */
                        LASSERT(data == olck);
                        osc_lock_blocking(env, dlmlock,
                                          olck, flag == LDLM_CB_BLOCKING);
                } else
                        cancel = 1;
                cl_lock_mutex_put(env, lock);
                osc_ast_data_put(env, olck);
        } else
                /*
                 * DLM lock exists, but there is no cl_lock attached to it.
                 * This is a `normal' race. cl_object and its cl_lock's can be
                 * removed by memory pressure, together with all pages.
                 */
                cancel = (flag == LDLM_CB_BLOCKING);

        if (cancel) {
                struct lustre_handle *lockh;

                lockh = &osc_env_info(env)->oti_handle;
                ldlm_lock2handle(dlmlock, lockh);
                result = ldlm_cli_cancel(lockh, LCF_ASYNC);
        } else
                result = 0;
        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)
{
        struct lu_env *env;
        struct cl_env_nest nest;
        int result;

        /*
         * This can be called in the context of outer IO, e.g.,
         *
         *     cl_enqueue()->...
         *       ->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 = osc_dlm_blocking_ast0(env, dlmlock, data, flag);
                cl_env_nested_put(&nest, env);
        } else {
                result = PTR_ERR(env);
                /*
                 * XXX This should never happen, as cl_lock is
                 * stuck. Pre-allocated environment a la vvp_inode_fini_env
                 * should be used.
                 */
                LBUG();
        }
        if (result != 0) {
                if (result == -ENODATA)
                        result = 0;
                else
                        CERROR("BAST failed: %d\n", result);
        }
        return result;
}

static int osc_ldlm_completion_ast(struct ldlm_lock *dlmlock,
                                   __u64 flags, void *data)
{
        struct cl_env_nest nest;
        struct lu_env *env;
        struct osc_lock *olck;
        struct cl_lock *lock;
        int result;
        int dlmrc;

        /* first, do dlm part of the work */
        dlmrc = ldlm_completion_ast_async(dlmlock, flags, data);
        /* then, notify cl_lock */
        env = cl_env_nested_get(&nest);
        if (!IS_ERR(env)) {
                olck = osc_ast_data_get(dlmlock);
                if (olck != NULL) {
                        lock = olck->ols_cl.cls_lock;
                        cl_lock_mutex_get(env, lock);
                        /*
                         * ldlm_handle_cp_callback() copied LVB from request
                         * to lock->l_lvb_data, store it in osc_lock.
                         */
                        LASSERT(dlmlock->l_lvb_data != NULL);
                        lock_res_and_lock(dlmlock);
                        olck->ols_lvb = *(struct ost_lvb *)dlmlock->l_lvb_data;
                        if (olck->ols_lock == NULL) {
                                /*
                                 * upcall (osc_lock_upcall()) hasn't yet been
                                 * called. Do nothing now, upcall will bind
                                 * olck to dlmlock and signal the waiters.
                                 *
                                 * This maintains an invariant that osc_lock
                                 * and ldlm_lock are always bound when
                                 * osc_lock is in OLS_GRANTED state.
                                 */
                        } else if (dlmlock->l_granted_mode ==
                                   dlmlock->l_req_mode) {
                                osc_lock_granted(env, olck, dlmlock, dlmrc);
                        }
                        unlock_res_and_lock(dlmlock);

                        if (dlmrc != 0) {
                                CL_LOCK_DEBUG(D_ERROR, env, lock,
                                              "dlmlock returned %d\n", dlmrc);
                                cl_lock_error(env, lock, dlmrc);
                        }
                        cl_lock_mutex_put(env, lock);
                        osc_ast_data_put(env, olck);
                        result = 0;
                } else
                        result = -ELDLM_NO_LOCK_DATA;
                cl_env_nested_put(&nest, env);
        } else
                result = PTR_ERR(env);
        return dlmrc ?: result;
}

static int osc_ldlm_glimpse_ast(struct ldlm_lock *dlmlock, void *data)
{
        struct ptlrpc_request *req = data;
        struct osc_lock *olck;
        struct cl_lock *lock;
        struct cl_object *obj;
        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)) {
                /* osc_ast_data_get() has to go after environment is
                 * allocated, because osc_ast_data() acquires a
                 * reference to a lock, and it can only be released in
                 * environment.
                 */
                olck = osc_ast_data_get(dlmlock);
                if (olck != NULL) {
                        lock = olck->ols_cl.cls_lock;
                        /* 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);
                                obj = lock->cll_descr.cld_obj;
                                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);
                        osc_ast_data_put(env, olck);
                } 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 unsigned long osc_lock_weigh(const struct lu_env *env,
                                    const struct cl_lock_slice *slice)
{
        /*
         * don't need to grab coh_page_guard since we don't care the exact #
         * of pages..
         */
        return cl_object_header(slice->cls_obj)->coh_pages;
}

static void osc_lock_build_einfo(const struct lu_env *env,
                                 const struct cl_lock *clock,
                                 struct osc_lock *lock,
                                 struct ldlm_enqueue_info *einfo)
{
        enum cl_lock_mode mode;

        mode = clock->cll_descr.cld_mode;
        if (mode == CLM_PHANTOM)
                /*
                 * For now, enqueue all glimpse locks in read mode. In the
                 * future, client might choose to enqueue LCK_PW lock for
                 * glimpse on a file opened for write.
                 */
                mode = CLM_READ;

        einfo->ei_type = LDLM_EXTENT;
        einfo->ei_mode = osc_cl_lock2ldlm(mode);
        einfo->ei_cb_bl = osc_ldlm_blocking_ast;
        einfo->ei_cb_cp = osc_ldlm_completion_ast;
        einfo->ei_cb_gl = osc_ldlm_glimpse_ast;
        einfo->ei_cbdata = lock; /* 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 int osc_lock_compatible(const struct osc_lock *qing,
                               const struct osc_lock *qed)
{
        enum cl_lock_mode qing_mode;
        enum cl_lock_mode qed_mode;

        qing_mode = qing->ols_cl.cls_lock->cll_descr.cld_mode;
        if (qed->ols_glimpse &&
            (qed->ols_state >= OLS_UPCALL_RECEIVED || qing_mode == CLM_READ))
                return 1;

        qed_mode = qed->ols_cl.cls_lock->cll_descr.cld_mode;
        return ((qing_mode == CLM_READ) && (qed_mode == CLM_READ));
}

/**
 * Cancel all conflicting locks and wait for them to be destroyed.
 *
 * This function is used for two purposes:
 *
 *     - early cancel all conflicting locks before starting IO, and
 *
 *     - guarantee that pages added to the page cache by lockless IO are never
 *       covered by locks other than lockless IO lock, and, hence, are not
 *       visible to other threads.
 */
static int osc_lock_enqueue_wait(const struct lu_env *env,
                                 const struct osc_lock *olck)
{
        struct cl_lock *lock = olck->ols_cl.cls_lock;
        struct cl_lock_descr *descr = &lock->cll_descr;
        struct cl_object_header *hdr = cl_object_header(descr->cld_obj);
        struct cl_lock *scan;
        struct cl_lock *conflict = NULL;
        int lockless = osc_lock_is_lockless(olck);
        int rc = 0;

        LASSERT(cl_lock_is_mutexed(lock));

        /* make it enqueue anyway for glimpse lock, because we actually
         * don't need to cancel any conflicting locks. */
        if (olck->ols_glimpse)
                return 0;

        spin_lock(&hdr->coh_lock_guard);
        list_for_each_entry(scan, &hdr->coh_locks, cll_linkage) {
                struct cl_lock_descr *cld = &scan->cll_descr;
                const struct osc_lock *scan_ols;

                if (scan == lock)
                        break;

                if (scan->cll_state < CLS_QUEUING ||
                    scan->cll_state == CLS_FREEING ||
                    cld->cld_start > descr->cld_end ||
                    cld->cld_end < descr->cld_start)
                        continue;

                /* overlapped and living locks. */

                /* We're not supposed to give up group lock. */
                if (scan->cll_descr.cld_mode == CLM_GROUP) {
                        LASSERT(descr->cld_mode != CLM_GROUP ||
                                descr->cld_gid != scan->cll_descr.cld_gid);
                        continue;
                }

                scan_ols = osc_lock_at(scan);

                /* We need to cancel the compatible locks if we're enqueuing
                 * a lockless lock, for example:
                 * imagine that client has PR lock on [0, 1000], and thread T0
                 * is doing lockless IO in [500, 1500] region. Concurrent
                 * thread T1 can see lockless data in [500, 1000], which is
                 * wrong, because these data are possibly stale. */
                if (!lockless && osc_lock_compatible(olck, scan_ols))
                        continue;

                cl_lock_get_trust(scan);
                conflict = scan;
                break;
        }
        spin_unlock(&hdr->coh_lock_guard);

        if (conflict) {
                if (lock->cll_descr.cld_mode == CLM_GROUP) {
                        /* we want a group lock but a previous lock request
                         * conflicts, we do not wait but return 0 so the
                         * request is send to the server
                         */
                        CDEBUG(D_DLMTRACE, "group lock %p is conflicted with %p, no wait, send to server\n",
                               lock, conflict);
                        cl_lock_put(env, conflict);
                        rc = 0;
                } else {
                        CDEBUG(D_DLMTRACE, "lock %p is conflicted with %p, will wait\n",
                               lock, conflict);
                        LASSERT(lock->cll_conflict == NULL);
                        lu_ref_add(&conflict->cll_reference, "cancel-wait",
                                   lock);
                        lock->cll_conflict = conflict;
                        rc = CLO_WAIT;
                }
        }
        return rc;
}

/**
 * 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, __u32 enqflags)
{
        struct osc_lock *ols = cl2osc_lock(slice);
        struct cl_lock *lock = ols->ols_cl.cls_lock;
        int result;

        LASSERT(cl_lock_is_mutexed(lock));
        LASSERTF(ols->ols_state == OLS_NEW,
                 "Impossible state: %d\n", ols->ols_state);

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

        result = osc_lock_enqueue_wait(env, ols);
        if (result == 0) {
                if (!osc_lock_is_lockless(ols)) {
                        struct osc_object *obj = cl2osc(slice->cls_obj);
                        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 ldlm_enqueue_info *einfo = &ols->ols_einfo;

                        /* lock will be passed as upcall cookie,
                         * hold ref to prevent to be released. */
                        cl_lock_hold_add(env, lock, "upcall", lock);
                        /* a user for lock also */
                        cl_lock_user_add(env, lock);
                        ols->ols_state = OLS_ENQUEUED;

                        /*
                         * XXX: this is possible blocking point as
                         * ldlm_lock_match(LDLM_FL_LVB_READY) waits for
                         * LDLM_CP_CALLBACK.
                         */
                        ostid_build_res_name(&obj->oo_oinfo->loi_oi, resname);
                        osc_lock_build_policy(env, lock, policy);
                        result = osc_enqueue_base(osc_export(obj), resname,
                                          &ols->ols_flags, policy,
                                          &ols->ols_lvb,
                                          obj->oo_oinfo->loi_kms_valid,
                                          osc_lock_upcall,
                                          ols, einfo, &ols->ols_handle,
                                          PTLRPCD_SET, 1, ols->ols_agl);
                        if (result != 0) {
                                cl_lock_user_del(env, lock);
                                cl_lock_unhold(env, lock, "upcall", lock);
                                if (unlikely(result == -ECANCELED)) {
                                        ols->ols_state = OLS_NEW;
                                        result = 0;
                                }
                        }
                } else {
                        ols->ols_state = OLS_GRANTED;
                        ols->ols_owner = osc_env_io(env);
                }
        }
        LASSERT(ergo(ols->ols_glimpse, !osc_lock_is_lockless(ols)));
        return result;
}

static int osc_lock_wait(const struct lu_env *env,
                         const struct cl_lock_slice *slice)
{
        struct osc_lock *olck = cl2osc_lock(slice);
        struct cl_lock *lock = olck->ols_cl.cls_lock;

        LINVRNT(osc_lock_invariant(olck));

        if (olck->ols_glimpse && olck->ols_state >= OLS_UPCALL_RECEIVED) {
                if (olck->ols_flags & LDLM_FL_LVB_READY) {
                        return 0;
                } else if (olck->ols_agl) {
                        if (lock->cll_flags & CLF_FROM_UPCALL)
                                /* It is from enqueue RPC reply upcall for
                                 * updating state. Do not re-enqueue. */
                                return -ENAVAIL;
                        olck->ols_state = OLS_NEW;
                } else {
                        LASSERT(lock->cll_error);
                        return lock->cll_error;
                }
        }

        if (olck->ols_state == OLS_NEW) {
                int rc;

                LASSERT(olck->ols_agl);
                olck->ols_agl = 0;
                olck->ols_flags &= ~LDLM_FL_BLOCK_NOWAIT;
                rc = osc_lock_enqueue(env, slice, NULL, CEF_ASYNC | CEF_MUST);
                if (rc != 0)
                        return rc;
                else
                        return CLO_REENQUEUED;
        }

        LASSERT(equi(olck->ols_state >= OLS_UPCALL_RECEIVED &&
                     lock->cll_error == 0, olck->ols_lock != NULL));

        return lock->cll_error ?: olck->ols_state >= OLS_GRANTED ? 0 : CLO_WAIT;
}

/**
 * An implementation of cl_lock_operations::clo_use() method that pins cached
 * lock.
 */
static int osc_lock_use(const struct lu_env *env,
                        const struct cl_lock_slice *slice)
{
        struct osc_lock *olck = cl2osc_lock(slice);
        int rc;

        LASSERT(!olck->ols_hold);

        /*
         * Atomically check for LDLM_FL_CBPENDING and addref a lock if this
         * flag is not set. This protects us from a concurrent blocking ast.
         */
        rc = ldlm_lock_addref_try(&olck->ols_handle, olck->ols_einfo.ei_mode);
        if (rc == 0) {
                olck->ols_hold = 1;
                olck->ols_state = OLS_GRANTED;
        } else {
                struct cl_lock *lock;

                /*
                 * Lock is being cancelled somewhere within
                 * ldlm_handle_bl_callback(): LDLM_FL_CBPENDING is already
                 * set, but osc_ldlm_blocking_ast() hasn't yet acquired
                 * cl_lock mutex.
                 */
                lock = slice->cls_lock;
                LASSERT(lock->cll_state == CLS_INTRANSIT);
                LASSERT(lock->cll_users > 0);
                /* set a flag for osc_dlm_blocking_ast0() to signal the
                 * lock.*/
                olck->ols_ast_wait = 1;
                rc = CLO_WAIT;
        }
        return rc;
}

static int osc_lock_flush(struct osc_lock *ols, int discard)
{
        struct cl_lock *lock = ols->ols_cl.cls_lock;
        struct cl_env_nest nest;
        struct lu_env *env;
        int result = 0;

        env = cl_env_nested_get(&nest);
        if (!IS_ERR(env)) {
                struct osc_object *obj = cl2osc(ols->ols_cl.cls_obj);
                struct cl_lock_descr *descr = &lock->cll_descr;
                int rc = 0;

                if (descr->cld_mode >= CLM_WRITE) {
                        result = osc_cache_writeback_range(env, obj,
                                        descr->cld_start, descr->cld_end,
                                        1, discard);
                        LDLM_DEBUG(ols->ols_lock,
                                "lock %p: %d pages were %s.\n", lock, result,
                                discard ? "discarded" : "written");
                        if (result > 0)
                                result = 0;
                }

                rc = cl_lock_discard_pages(env, lock);
                if (result == 0 && rc < 0)
                        result = rc;

                cl_env_nested_put(&nest, env);
        } else
                result = PTR_ERR(env);
        if (result == 0) {
                ols->ols_flush = 1;
                LINVRNT(!osc_lock_has_pages(ols));
        }
        return result;
}

/**
 * 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 cl_lock *lock = slice->cls_lock;
        struct osc_lock *olck = cl2osc_lock(slice);
        struct ldlm_lock *dlmlock = olck->ols_lock;
        int result = 0;
        int discard;

        LASSERT(cl_lock_is_mutexed(lock));
        LINVRNT(osc_lock_invariant(olck));

        if (dlmlock != NULL) {
                int do_cancel;

                discard = !!(dlmlock->l_flags & LDLM_FL_DISCARD_DATA);
                if (olck->ols_state >= OLS_GRANTED)
                        result = osc_lock_flush(olck, discard);
                osc_lock_unhold(olck);

                lock_res_and_lock(dlmlock);
                /* Now that we're the only user of dlm read/write reference,
                 * mostly the ->l_readers + ->l_writers should be zero.
                 * However, there is a corner case.
                 * See bug 18829 for details.*/
                do_cancel = (dlmlock->l_readers == 0 &&
                             dlmlock->l_writers == 0);
                dlmlock->l_flags |= LDLM_FL_CBPENDING;
                unlock_res_and_lock(dlmlock);
                if (do_cancel)
                        result = ldlm_cli_cancel(&olck->ols_handle, LCF_ASYNC);
                if (result < 0)
                        CL_LOCK_DEBUG(D_ERROR, env, lock,
                                      "lock %p cancel failure with error(%d)\n",
                                      lock, result);
        }
        olck->ols_state = OLS_CANCELLED;
        olck->ols_flags &= ~LDLM_FL_LVB_READY;
        osc_lock_detach(env, olck);
}

static int osc_lock_has_pages(struct osc_lock *olck)
{
        return 0;
}

static void osc_lock_delete(const struct lu_env *env,
                            const struct cl_lock_slice *slice)
{
        struct osc_lock *olck;

        olck = cl2osc_lock(slice);
        if (olck->ols_glimpse) {
                LASSERT(!olck->ols_hold);
                LASSERT(!olck->ols_lock);
                return;
        }

        LINVRNT(osc_lock_invariant(olck));
        LINVRNT(!osc_lock_has_pages(olck));

        osc_lock_unhold(olck);
        osc_lock_detach(env, olck);
}

/**
 * Implements cl_lock_operations::clo_state() method for osc layer.
 *
 * Maintains osc_lock::ols_owner field.
 *
 * This assumes that lock always enters CLS_HELD (from some other state) in
 * the same IO context as one that requested the lock. This should not be a
 * problem, because context is by definition shared by all activity pertaining
 * to the same high-level IO.
 */
static void osc_lock_state(const struct lu_env *env,
                           const struct cl_lock_slice *slice,
                           enum cl_lock_state state)
{
        struct osc_lock *lock = cl2osc_lock(slice);

        /*
         * XXX multiple io contexts can use the lock at the same time.
         */
        LINVRNT(osc_lock_invariant(lock));
        if (state == CLS_HELD && slice->cls_lock->cll_state != CLS_HELD) {
                struct osc_io *oio = osc_env_io(env);

                LASSERT(lock->ols_owner == NULL);
                lock->ols_owner = oio;
        } else if (state != CLS_HELD)
                lock->ols_owner = NULL;
}

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);

        /*
         * XXX print ldlm lock and einfo properly.
         */
        (*p)(env, cookie, "%p %#16llx %#llx %d %p ",
             lock->ols_lock, 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 int osc_lock_fits_into(const struct lu_env *env,
                              const struct cl_lock_slice *slice,
                              const struct cl_lock_descr *need,
                              const struct cl_io *io)
{
        struct osc_lock *ols = cl2osc_lock(slice);

        if (need->cld_enq_flags & CEF_NEVER)
                return 0;

        if (ols->ols_state >= OLS_CANCELLED)
                return 0;

        if (need->cld_mode == CLM_PHANTOM) {
                if (ols->ols_agl)
                        return !(ols->ols_state > OLS_RELEASED);

                /*
                 * Note: the QUEUED lock can't be matched here, otherwise
                 * it might cause the deadlocks.
                 * In read_process,
                 * P1: enqueued read lock, create sublock1
                 * P2: enqueued write lock, create sublock2(conflicted
                 *     with sublock1).
                 * P1: Grant read lock.
                 * P1: enqueued glimpse lock(with holding sublock1_read),
                 *     matched with sublock2, waiting sublock2 to be granted.
                 *     But sublock2 can not be granted, because P1
                 *     will not release sublock1. Bang!
                 */
                if (ols->ols_state < OLS_GRANTED ||
                    ols->ols_state > OLS_RELEASED)
                        return 0;
        } else if (need->cld_enq_flags & CEF_MUST) {
                /*
                 * If the lock hasn't ever enqueued, it can't be matched
                 * because enqueue process brings in many information
                 * which can be used to determine things such as lockless,
                 * CEF_MUST, etc.
                 */
                if (ols->ols_state < OLS_UPCALL_RECEIVED &&
                    ols->ols_locklessable)
                        return 0;
        }
        return 1;
}

static const struct cl_lock_operations osc_lock_ops = {
        .clo_fini    = osc_lock_fini,
        .clo_enqueue = osc_lock_enqueue,
        .clo_wait    = osc_lock_wait,
        .clo_unuse   = osc_lock_unuse,
        .clo_use     = osc_lock_use,
        .clo_delete  = osc_lock_delete,
        .clo_state   = osc_lock_state,
        .clo_cancel  = osc_lock_cancel,
        .clo_weigh   = osc_lock_weigh,
        .clo_print   = osc_lock_print,
        .clo_fits_into = osc_lock_fits_into,
};

static int osc_lock_lockless_unuse(const struct lu_env *env,
                                   const struct cl_lock_slice *slice)
{
        struct osc_lock *ols = cl2osc_lock(slice);
        struct cl_lock *lock = slice->cls_lock;

        LASSERT(ols->ols_state == OLS_GRANTED);
        LINVRNT(osc_lock_invariant(ols));

        cl_lock_cancel(env, lock);
        cl_lock_delete(env, lock);
        return 0;
}

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

        result = osc_lock_flush(ols, 0);
        if (result)
                CERROR("Pages for lockless lock %p were not purged(%d)\n",
                       ols, result);
        ols->ols_state = OLS_CANCELLED;
}

static int osc_lock_lockless_wait(const struct lu_env *env,
                                  const struct cl_lock_slice *slice)
{
        struct osc_lock *olck = cl2osc_lock(slice);
        struct cl_lock *lock = olck->ols_cl.cls_lock;

        LINVRNT(osc_lock_invariant(olck));
        LASSERT(olck->ols_state >= OLS_UPCALL_RECEIVED);

        return lock->cll_error;
}

static void osc_lock_lockless_state(const struct lu_env *env,
                                    const struct cl_lock_slice *slice,
                                    enum cl_lock_state state)
{
        struct osc_lock *lock = cl2osc_lock(slice);

        LINVRNT(osc_lock_invariant(lock));
        if (state == CLS_HELD) {
                struct osc_io *oio = osc_env_io(env);

                LASSERT(ergo(lock->ols_owner, lock->ols_owner == oio));
                lock->ols_owner = oio;

                /* set the io to be lockless if this lock is for io's
                 * host object */
                if (cl_object_same(oio->oi_cl.cis_obj, slice->cls_obj))
                        oio->oi_lockless = 1;
        }
}

static int osc_lock_lockless_fits_into(const struct lu_env *env,
                                       const struct cl_lock_slice *slice,
                                       const struct cl_lock_descr *need,
                                       const struct cl_io *io)
{
        struct osc_lock *lock = cl2osc_lock(slice);

        if (!(need->cld_enq_flags & CEF_NEVER))
                return 0;

        /* lockless lock should only be used by its owning io. b22147 */
        return (lock->ols_owner == osc_env_io(env));
}

static const struct cl_lock_operations osc_lock_lockless_ops = {
        .clo_fini      = osc_lock_fini,
        .clo_enqueue   = osc_lock_enqueue,
        .clo_wait      = osc_lock_lockless_wait,
        .clo_unuse     = osc_lock_lockless_unuse,
        .clo_state     = osc_lock_lockless_state,
        .clo_fits_into = osc_lock_lockless_fits_into,
        .clo_cancel    = osc_lock_lockless_cancel,
        .clo_print     = osc_lock_print
};

int osc_lock_init(const struct lu_env *env,
                  struct cl_object *obj, struct cl_lock *lock,
                  const struct cl_io *unused)
{
        struct osc_lock *clk;
        int result;

        clk = kmem_cache_alloc(osc_lock_kmem, GFP_NOFS | __GFP_ZERO);
        if (clk != NULL) {
                __u32 enqflags = lock->cll_descr.cld_enq_flags;

                osc_lock_build_einfo(env, lock, clk, &clk->ols_einfo);
                atomic_set(&clk->ols_pageref, 0);
                clk->ols_state = OLS_NEW;

                clk->ols_flags = osc_enq2ldlm_flags(enqflags);
                clk->ols_agl = !!(enqflags & CEF_AGL);
                if (clk->ols_agl)
                        clk->ols_flags |= LDLM_FL_BLOCK_NOWAIT;
                if (clk->ols_flags & LDLM_FL_HAS_INTENT)
                        clk->ols_glimpse = 1;

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

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

                LDLM_DEBUG_NOLOCK("lock %p, osc lock %p, flags %llx\n",
                                lock, clk, clk->ols_flags);

                result = 0;
        } else
                result = -ENOMEM;
        return result;
}

int osc_dlm_lock_pageref(struct ldlm_lock *dlm)
{
        struct osc_lock *olock;
        int rc = 0;

        spin_lock(&osc_ast_guard);
        olock = dlm->l_ast_data;
        /*
         * there's a very rare race with osc_page_addref_lock(), but that
         * doesn't matter because in the worst case we don't cancel a lock
         * which we actually can, that's no harm.
         */
        if (olock != NULL &&
            atomic_add_return(_PAGEREF_MAGIC,
                                  &olock->ols_pageref) != _PAGEREF_MAGIC) {
                atomic_sub(_PAGEREF_MAGIC, &olock->ols_pageref);
                rc = 1;
        }
        spin_unlock(&osc_ast_guard);
        return rc;
}

/** @} osc */