/* -*- 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; int conflicting = 0; 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; /* Locks are compatible, overlap doesn't matter */ /* Until bug 20 is fixed, try to avoid granting overlapping * locks on one client (they take a long time to cancel) */ if (lockmode_compat(lock->l_req_mode, req_mode) && lock->l_export != req->l_export) continue; /* If this is a high-traffic lock, don't grow downwards at all * or grow upwards too much */ ++conflicting; if (conflicting > 4) new_ex->start = req_start; /* If lock doesn't overlap new_ex, skip it. */ if (l_extent->end < new_ex->start || l_extent->start > new_ex->end) 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 previous request. * l_req_extent->end strictly < req_start, checked above. */ if (l_extent->start < req_start && new_ex->start != req_start) { if (l_extent->end >= req_start) 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); } } #define LDLM_MAX_GROWN_EXTENT (32 * 1024 * 1024 - 1) if (conflicting > 32 && (req_mode == LCK_PW || req_mode == LCK_CW)) { if (req_end < req_start + LDLM_MAX_GROWN_EXTENT) new_ex->end = min(req_start + LDLM_MAX_GROWN_EXTENT, new_ex->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}; if (lock->l_req_mode == LCK_GROUP) return; 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. * * 0 if the lock is not compatible * 1 if the lock is compatible * 2 if this group lock is compatible and requires no further checking * negative error, such as EWOULDBLOCK for group locks */ static int ldlm_extent_compat_queue(struct list_head *queue, struct ldlm_lock *req, int *flags, struct list_head *work_list, struct list_head **insertp) { struct list_head *tmp; struct list_head *save = NULL; struct ldlm_lock *lock = NULL; ldlm_mode_t req_mode = req->l_req_mode; int compat = 1; int found = 0; ENTRY; lockmode_verify(req_mode); /* Extent locks are only queued once. We can get back here with * insertp != NULL if the blocking ASTs returned -ERESTART. */ if (!list_empty(&req->l_res_link)) insertp = NULL; if (req->l_req_mode != LCK_GROUP) { __u64 req_start = req->l_req_extent.start; __u64 req_end = req->l_req_extent.end; list_for_each(tmp, queue) { lock = list_entry(tmp, struct ldlm_lock, l_res_link); if (req == lock) break; if (lock->l_req_mode == LCK_GROUP) { if (*flags & LDLM_FL_BLOCK_NOWAIT) RETURN(-EWOULDBLOCK); /* No blocking ASTs are sent for group locks. */ compat = 0; /* there's a blocking group lock in front * of us on the queue. It can be held * indefinitely, so don't timeout. */ if (insertp) { *flags |= LDLM_FL_NO_TIMEOUT; /* lock_bitlock(req) is held here. */ req->l_flags |= LDLM_FL_NO_TIMEOUT; } if (work_list) continue; else break; } /* locks are compatible, overlap doesn't matter */ if (lockmode_compat(lock->l_req_mode, req_mode)) continue; if (lock->l_policy_data.l_extent.end < req_start || lock->l_policy_data.l_extent.start > req_end) continue; compat = 0; if (!work_list) break; if (lock->l_blocking_ast) ldlm_add_ast_work_item(lock, req, work_list); } if (insertp) *insertp = queue; RETURN(compat); } list_for_each(tmp, queue) { lock = list_entry(tmp, struct ldlm_lock, l_res_link); if (req == lock) break; if (lock->l_req_mode != LCK_GROUP) { if (lock->l_req_mode != lock->l_granted_mode) { /* we must be traversing the waitq. */ /* If a group lock was already found then * req can be queued before any extent locks * that come after the found group lock. */ if (found) break; if (!insertp) { /* We've hit a conflicting extent lock * on the waitq before hitting the req * group lock. See comments below. */ compat = 0; break; } /* Group locks are not normally blocked by * waiting PR|PW locks. */ /* If NO_TIMEOUT was sent back to the client * we can queue the group lock in front of * this extent lock. */ if (lock->l_flags & LDLM_FL_NO_TIMEOUT) { if (save == NULL) save = tmp; continue; } /* If we did NOT send NO_TIMEOUT back to the * client for this extent lock then the client * could possibly timeout if we queue this * group lock before it, so don't. This is the * only way to get a conflicting extent lock * in front of a group lock on the waitq. */ } compat = 0; if (!work_list) { LASSERT(save == NULL); break; } /* If we previously skipped over some extent locks * because we thought we were going to queue the * group lock in front of them then we need to go back * and send blocking ASTs for the locks we skipped. */ if (save != NULL) { struct ldlm_lock *lck2; for (; save != tmp; save = save->next) { lck2 = list_entry(save, struct ldlm_lock, l_res_link); /* If there was a group lock after save * then we would have exited this loop * above. */ LASSERT(lck2->l_req_mode!=LCK_GROUP); if (lck2->l_blocking_ast) { ldlm_add_ast_work_item(lck2,req, work_list); } } save = NULL; } if (lock->l_blocking_ast) ldlm_add_ast_work_item(lock, req, work_list); continue; } /* If it was safe to insert a group lock at save, * i.e. save != NULL, then this group lock already * on the queue would have been inserted before save. */ LASSERT(save == NULL); /* Note: no blocking ASTs are sent for group locks. */ if (lock->l_policy_data.l_extent.gid == req->l_policy_data.l_extent.gid) { /* group locks with this gid already on the waitq. */ found = 2; if (lock->l_req_mode == lock->l_granted_mode) { /* if a group lock with this gid has already * been granted then grant this one. */ compat = 2; break; } } else { if (found == 2) break; /* group locks already exist on the queue. */ found = 1; if (*flags & LDLM_FL_BLOCK_NOWAIT) RETURN(-EWOULDBLOCK); compat = 0; /* there's a blocking group lock in front * of us on the queue. It can be held * indefinitely, so don't timeout. */ *flags |= LDLM_FL_NO_TIMEOUT; /* the only reason to continue traversing the * list at this point is to find the proper * place to insert the lock in the waitq. */ if (!insertp) break; } } if (insertp != NULL) { if (save != NULL) *insertp = save; else *insertp = tmp; } 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 list_head *work_list) { struct ldlm_resource *res = lock->l_resource; struct list_head rpc_list = LIST_HEAD_INIT(rpc_list); struct list_head *insertp = NULL; int rc, rc2; ENTRY; LASSERT(list_empty(&res->lr_converting)); *err = ELDLM_OK; if (!first_enq) { /* -EWOULDBLOCK can't occur here since (flags & BLOCK_NOWAIT) * lock requests would either be granted or fail on their * first_enq. flags should always be zero here, and if that * ever changes we want to find out. */ LASSERT(*flags == 0); rc = ldlm_extent_compat_queue(&res->lr_granted, lock, flags, NULL, NULL); if (rc == 1) { rc = ldlm_extent_compat_queue(&res->lr_waiting, lock, flags, NULL, NULL); } if (rc == 0) RETURN(LDLM_ITER_STOP); ldlm_resource_unlink_lock(lock); ldlm_extent_policy(res, lock, flags); lock_bitlock(lock); lock->l_flags &= ~LDLM_FL_NO_TIMEOUT; unlock_bitlock(lock); ldlm_grant_lock(lock, work_list); RETURN(LDLM_ITER_CONTINUE); } restart: rc = ldlm_extent_compat_queue(&res->lr_granted, lock, flags, &rpc_list, NULL); if (rc < 0) GOTO(destroylock, rc); if (rc == 2) goto grant; /* Traverse the waiting list in case there are other conflicting * lock requests ahead of us in the queue and send blocking ASTs */ rc2 = ldlm_extent_compat_queue(&res->lr_waiting, lock, flags, &rpc_list, &insertp); if (rc2 < 0) GOTO(destroylock, rc); if (rc + rc2 == 2) { grant: ldlm_extent_policy(res, lock, flags); ldlm_resource_unlink_lock(lock); lock->l_flags &= ~LDLM_FL_NO_TIMEOUT; ldlm_grant_lock(lock, NULL); } else { /* If either of the compat_queue()s returned failure, 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, insertp, lock); unlock_res(res); rc = ldlm_run_bl_ast_work(&rpc_list); lock_res(res); if (rc == -ERESTART) GOTO(restart, -ERESTART); *flags |= LDLM_FL_BLOCK_GRANTED; } RETURN(0); destroylock: list_del_init(&lock->l_res_link); unlock_res(res); ldlm_lock_destroy(lock); lock_res(res); *err = rc; RETURN(rc); } /* 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. * Caller must hold ns_lock already. * * 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; /* don't let another thread in ldlm_extent_shift_kms race in * just after we finish and take our lock into account in its * calculation of the kms */ lock->l_flags |= LDLM_FL_KMS_IGNORE; list_for_each(tmp, &res->lr_granted) { lck = list_entry(tmp, struct ldlm_lock, l_res_link); if (lck->l_flags & LDLM_FL_KMS_IGNORE) continue; if (lck->l_policy_data.l_extent.end >= old_kms) RETURN(old_kms); /* This extent _has_ to be smaller than old_kms (checked above) * so kms can only ever be smaller or the same as old_kms. */ if (lck->l_policy_data.l_extent.end + 1 > kms) kms = lck->l_policy_data.l_extent.end + 1; } LASSERTF(kms <= old_kms, "kms "LPU64" old_kms "LPU64"\n", kms, old_kms); RETURN(kms); }