/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*- * vim:expandtab:shiftwidth=8:tabstop=8: * * Copyright (c) 2002, 2003 Cluster File Systems, Inc. * Author: Peter Braam * Author: Phil Schwan * * This file is part of Lustre, http://www.lustre.org. * * Lustre is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. * * Lustre 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 for more details. * * You should have received a copy of the GNU General Public License * along with Lustre; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #define DEBUG_SUBSYSTEM S_LDLM #ifndef __KERNEL__ # include #endif #include #include #include #include "ldlm_internal.h" /* The purpose of this function is to return: * - the maximum extent * - containing the requested extent * - and not overlapping existing conflicting extents outside the requested one */ static void ldlm_extent_internal_policy(struct list_head *queue, struct ldlm_lock *req, struct ldlm_extent *new_ex) { struct list_head *tmp; ldlm_mode_t req_mode = req->l_req_mode; __u64 req_start = req->l_req_extent.start; __u64 req_end = req->l_req_extent.end; ENTRY; lockmode_verify(req_mode); list_for_each(tmp, queue) { struct ldlm_lock *lock; struct ldlm_extent *l_extent; lock = list_entry(tmp, struct ldlm_lock, l_res_link); l_extent = &lock->l_policy_data.l_extent; if (new_ex->start == req_start && new_ex->end == req_end) { EXIT; return; } /* Don't conflict with ourselves */ if (req == lock) continue; /* If lock doesn't overlap new_ex, skip it. */ if (l_extent->end < new_ex->start || l_extent->start > new_ex->end) continue; /* Locks are compatible, overlap doesn't matter */ if (lockmode_compat(lock->l_req_mode, req_mode)) continue; /* Locks conflicting in requested extents and we can't satisfy * both locks, so ignore it. Either we will ping-pong this * extent (we would regardless of what extent we granted) or * lock is unused and it shouldn't limit our extent growth. */ if (lock->l_req_extent.end >= req_start && lock->l_req_extent.start <= req_end) continue; /* We grow extents downwards only as far as they don't overlap * with already-granted locks, on the assumtion that clients * will be writing beyond the initial requested end and would * then need to enqueue a new lock beyond the previous request. * We don't grow downwards if there are lots of lockers. */ if (l_extent->start < req_start) { if (atomic_read(&req->l_resource->lr_refcount) > 20) new_ex->start = req_start; else new_ex->start = min(l_extent->end+1, req_start); } /* If we need to cancel this lock anyways because our request * overlaps the granted lock, we grow up to its requested * extent start instead of limiting this extent, assuming that * clients are writing forwards and the lock had over grown * its extent downwards before we enqueued our request. */ if (l_extent->end > req_end) { if (l_extent->start <= req_end) new_ex->end = max(lock->l_req_extent.start - 1, req_end); else new_ex->end = max(l_extent->start - 1, req_end); } } EXIT; } /* In order to determine the largest possible extent we can grant, we need * to scan all of the queues. */ static void ldlm_extent_policy(struct ldlm_resource *res, struct ldlm_lock *lock, int *flags) { struct ldlm_extent new_ex = { .start = 0, .end = ~0}; ldlm_extent_internal_policy(&res->lr_granted, lock, &new_ex); ldlm_extent_internal_policy(&res->lr_waiting, lock, &new_ex); if (new_ex.start != lock->l_policy_data.l_extent.start || new_ex.end != lock->l_policy_data.l_extent.end) { *flags |= LDLM_FL_LOCK_CHANGED; lock->l_policy_data.l_extent.start = new_ex.start; lock->l_policy_data.l_extent.end = new_ex.end; } } /* Determine if the lock is compatible with all locks on the queue. * We stop walking the queue if we hit ourselves so we don't take * conflicting locks enqueued after us into accound, or we'd wait forever. */ static int ldlm_extent_compat_queue(struct list_head *queue, struct ldlm_lock *req, int send_cbs) { struct list_head *tmp; struct ldlm_lock *lock; ldlm_mode_t req_mode = req->l_req_mode; __u64 req_start = req->l_req_extent.start; __u64 req_end = req->l_req_extent.end; int compat = 1; ENTRY; lockmode_verify(req_mode); list_for_each(tmp, queue) { lock = list_entry(tmp, struct ldlm_lock, l_res_link); if (req == lock) RETURN(compat); /* locks are compatible, overlap doesn't matter */ if (lockmode_compat(lock->l_req_mode, req_mode)) continue; /* if lock doesn't overlap skip it */ if (lock->l_policy_data.l_extent.end < req_start || lock->l_policy_data.l_extent.start > req_end) continue; if (!send_cbs) RETURN(0); compat = 0; if (lock->l_blocking_ast) ldlm_add_ast_work_item(lock, req, NULL, 0); } RETURN(compat); } /* If first_enq is 0 (ie, called from ldlm_reprocess_queue): * - blocking ASTs have already been sent * - the caller has already initialized req->lr_tmp * - must call this function with the ns lock held * * If first_enq is 1 (ie, called from ldlm_lock_enqueue): * - blocking ASTs have not been sent * - the caller has NOT initialized req->lr_tmp, so we must * - must call this function with the ns lock held once */ int ldlm_process_extent_lock(struct ldlm_lock *lock, int *flags, int first_enq, ldlm_error_t *err) { struct ldlm_resource *res = lock->l_resource; struct list_head rpc_list = LIST_HEAD_INIT(rpc_list); int rc; ENTRY; LASSERT(list_empty(&res->lr_converting)); if (!first_enq) { LASSERT(res->lr_tmp != NULL); rc = ldlm_extent_compat_queue(&res->lr_granted, lock, 0); if (!rc) RETURN(LDLM_ITER_STOP); rc = ldlm_extent_compat_queue(&res->lr_waiting, lock, 0); if (!rc) RETURN(LDLM_ITER_STOP); ldlm_resource_unlink_lock(lock); ldlm_extent_policy(res, lock, flags); ldlm_grant_lock(lock, NULL, 0, 1); RETURN(LDLM_ITER_CONTINUE); } restart: LASSERT(res->lr_tmp == NULL); res->lr_tmp = &rpc_list; rc = ldlm_extent_compat_queue(&res->lr_granted, lock, 1); rc += ldlm_extent_compat_queue(&res->lr_waiting, lock, 1); res->lr_tmp = NULL; if (rc != 2) { /* If either of the compat_queue()s returned 0, then we * have ASTs to send and must go onto the waiting list. * * bug 2322: we used to unlink and re-add here, which was a * terrible folly -- if we goto restart, we could get * re-ordered! Causes deadlock, because ASTs aren't sent! */ if (list_empty(&lock->l_res_link)) ldlm_resource_add_lock(res, &res->lr_waiting, lock); l_unlock(&res->lr_namespace->ns_lock); rc = ldlm_run_ast_work(res->lr_namespace, &rpc_list); l_lock(&res->lr_namespace->ns_lock); if (rc == -ERESTART) GOTO(restart, -ERESTART); *flags |= LDLM_FL_BLOCK_GRANTED; } else { ldlm_extent_policy(res, lock, flags); ldlm_resource_unlink_lock(lock); ldlm_grant_lock(lock, NULL, 0, 0); } RETURN(0); } /* When a lock is cancelled by a client, the KMS may undergo change if this * is the "highest lock". This function returns the new KMS value. * * NB: A lock on [x,y] protects a KMS of up to y + 1 bytes! */ __u64 ldlm_extent_shift_kms(struct ldlm_lock *lock, __u64 old_kms) { struct ldlm_resource *res = lock->l_resource; struct list_head *tmp; struct ldlm_lock *lck; __u64 kms = 0; ENTRY; l_lock(&res->lr_namespace->ns_lock); list_for_each(tmp, &res->lr_granted) { lck = list_entry(tmp, struct ldlm_lock, l_res_link); if (lock == lck) continue; if (lck->l_policy_data.l_extent.end >= old_kms) GOTO(out, kms = old_kms); kms = lck->l_policy_data.l_extent.end + 1; } GOTO(out, kms); out: l_unlock(&res->lr_namespace->ns_lock); return kms; }