lustre/ldlm/ldlm_extent.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  *  Copyright (c) 2002 Cluster File Systems, Inc.
   5  *   Author: Peter Braam <braam@clusterfs.com>
   6  *   Author: Phil Schwan <phil@clusterfs.com>
   7  *
   8  *   This file is part of Lustre, http://www.lustre.org.
   9  *
  10  *   Lustre is free software; you can redistribute it and/or
  11  *   modify it under the terms of version 2 of the GNU General Public
  12  *   License as published by the Free Software Foundation.
  13  *
  14  *   Lustre is distributed in the hope that it will be useful,
  15  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *   GNU General Public License for more details.
  18  *
  19  *   You should have received a copy of the GNU General Public License
  20  *   along with Lustre; if not, write to the Free Software
  21  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  22  */
  23
  24 #define DEBUG_SUBSYSTEM S_LDLM
  25 #ifndef __KERNEL__
  26 # include <liblustre.h>
  27 #endif
  28
  29 #include <linux/lustre_dlm.h>
  30 #include <linux/obd_support.h>
  31 #include <linux/lustre_lib.h>
  32
  33 /* This function will be called to judge if one extent overlaps with another */
  34 int ldlm_extent_compat(struct ldlm_lock *a, struct ldlm_lock *b)
  35 {
  36         if ((a->l_extent.start <= b->l_extent.end) &&
  37             (a->l_extent.end >=  b->l_extent.start))
  38                 RETURN(0);
  39
  40         RETURN(1);
  41 }
  42
  43 /* The purpose of this function is to return:
  44  * - the maximum extent
  45  * - containing the requested extent
  46  * - and not overlapping existing conflicting extents outside the requested one
  47  *
  48  * An alternative policy is to not shrink the new extent when conflicts exist.
  49  *
  50  * To reconstruct our formulas, take a deep breath. */
  51 static void policy_internal(struct list_head *queue, struct ldlm_extent *req_ex,
  52                             struct ldlm_extent *new_ex, ldlm_mode_t mode)
  53 {
  54         struct list_head *tmp;
  55
  56         list_for_each(tmp, queue) {
  57                 struct ldlm_lock *lock;
  58                 lock = list_entry(tmp, struct ldlm_lock, l_res_link);
  59
  60                 /* if lock doesn't overlap new_ex, skip it. */
  61                 if (lock->l_extent.end < new_ex->start ||
  62                     lock->l_extent.start > new_ex->end)
  63                         continue;
  64
  65                 /* Locks are compatible, overlap doesn't matter */
  66                 if (lockmode_compat(lock->l_req_mode, mode))
  67                         continue;
  68
  69                 if (lock->l_extent.start < req_ex->start) {
  70                         if (lock->l_extent.end == ~0) {
  71                                 new_ex->start = req_ex->start;
  72                                 new_ex->end = req_ex->end;
  73                                 return;
  74                         }
  75                         new_ex->start = MIN(lock->l_extent.end + 1,
  76                                             req_ex->start);
  77                 }
  78
  79                 if (lock->l_extent.end > req_ex->end) {
  80                         if (lock->l_extent.start == 0) {
  81                                 new_ex->start = req_ex->start;
  82                                 new_ex->end = req_ex->end;
  83                                 return;
  84                         }
  85                         new_ex->end = MAX(lock->l_extent.start - 1,
  86                                           req_ex->end);
  87                 }
  88         }
  89 }
  90
  91 /* apply the internal policy by walking all the lists */
  92 int ldlm_extent_policy(struct ldlm_namespace *ns, struct ldlm_lock **lockp,
  93                        void *req_cookie, ldlm_mode_t mode, int flags,
  94                        void *data)
  95 {
  96         struct ldlm_lock *lock = *lockp;
  97         struct ldlm_resource *res = lock->l_resource;
  98         struct ldlm_extent *req_ex = req_cookie;
  99         struct ldlm_extent new_ex;
 100         new_ex.start = 0;
 101         new_ex.end = ~0;
 102
 103         if (!res)
 104                 LBUG();
 105
 106         l_lock(&ns->ns_lock);
 107         policy_internal(&res->lr_granted, req_ex, &new_ex, mode);
 108         policy_internal(&res->lr_converting, req_ex, &new_ex, mode);
 109         policy_internal(&res->lr_waiting, req_ex, &new_ex, mode);
 110         l_unlock(&ns->ns_lock);
 111
 112         memcpy(&lock->l_extent, &new_ex, sizeof(new_ex));
 113
 114         LDLM_DEBUG(lock, "requested extent ["LPU64"->"LPU64"], new extent ["
 115                    LPU64"->"LPU64"]",
 116                    req_ex->start, req_ex->end, new_ex.start, new_ex.end);
 117
 118         if (new_ex.end != req_ex->end || new_ex.start != req_ex->start)
 119                 return ELDLM_LOCK_CHANGED;
 120         else
 121                 return 0;
 122 }