lustre/ldlm/ldlm_plain.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  *  Copyright (c) 2002, 2003 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
  26 #ifdef __KERNEL__
  27 #include <linux/lustre_dlm.h>
  28 #include <linux/obd_support.h>
  29 #include <linux/lustre_lib.h>
  30 #else
  31 #include <liblustre.h>
  32 #endif
  33
  34 #include "ldlm_internal.h"
  35
  36 static inline int
  37 ldlm_plain_compat_queue(struct list_head *queue, struct ldlm_lock *req,
  38                         int send_cbs)
  39 {
  40         struct list_head *tmp;
  41         struct ldlm_lock *lock;
  42         ldlm_mode_t req_mode = req->l_req_mode;
  43         int compat = 1;
  44         ENTRY;
  45
  46         lockmode_verify(req_mode);
  47
  48         list_for_each(tmp, queue) {
  49                 lock = list_entry(tmp, struct ldlm_lock, l_res_link);
  50
  51                 if (req == lock)
  52                         RETURN(compat);
  53
  54                 if (lockmode_compat(lock->l_req_mode, req_mode))
  55                         continue;
  56
  57                 if (!send_cbs)
  58                         RETURN(0);
  59
  60                 compat = 0;
  61                 if (lock->l_blocking_ast)
  62                         ldlm_add_ast_work_item(lock, req, NULL, 0);
  63         }
  64
  65         RETURN(compat);
  66 }
  67
  68 /* If first_enq is 0 (ie, called from ldlm_reprocess_queue):
  69  *   - blocking ASTs have already been sent
  70  *   - the caller has already initialized req->lr_tmp
  71  *   - must call this function with the ns lock held
  72  *
  73  * If first_enq is 1 (ie, called from ldlm_lock_enqueue):
  74  *   - blocking ASTs have not been sent
  75  *   - the caller has NOT initialized req->lr_tmp, so we must
  76  *   - must call this function with the ns lock held once */
  77 int ldlm_process_plain_lock(struct ldlm_lock *lock, int *flags, int first_enq,
  78                             ldlm_error_t *err)
  79 {
  80         struct ldlm_resource *res = lock->l_resource;
  81         struct list_head rpc_list = LIST_HEAD_INIT(rpc_list);
  82         int rc;
  83         ENTRY;
  84
  85         LASSERT(list_empty(&res->lr_converting));
  86
  87         if (!first_enq) {
  88                 LASSERT(res->lr_tmp != NULL);
  89                 rc = ldlm_plain_compat_queue(&res->lr_granted, lock, 0);
  90                 if (!rc)
  91                         RETURN(LDLM_ITER_STOP);
  92                 rc = ldlm_plain_compat_queue(&res->lr_waiting, lock, 0);
  93                 if (!rc)
  94                         RETURN(LDLM_ITER_STOP);
  95
  96                 ldlm_resource_unlink_lock(lock);
  97                 ldlm_grant_lock(lock, NULL, 0, 1);
  98                 RETURN(LDLM_ITER_CONTINUE);
  99         }
 100
 101  restart:
 102         LASSERT(res->lr_tmp == NULL);
 103         res->lr_tmp = &rpc_list;
 104         rc = ldlm_plain_compat_queue(&res->lr_granted, lock, 1);
 105         rc += ldlm_plain_compat_queue(&res->lr_waiting, lock, 1);
 106         res->lr_tmp = NULL;
 107
 108         if (rc != 2) {
 109                 /* If either of the compat_queue()s returned 0, then we
 110                  * have ASTs to send and must go onto the waiting list.
 111                  *
 112                  * bug 2322: we used to unlink and re-add here, which was a
 113                  * terrible folly -- if we goto restart, we could get
 114                  * re-ordered!  Causes deadlock, because ASTs aren't sent! */
 115                 if (list_empty(&lock->l_res_link))
 116                         ldlm_resource_add_lock(res, &res->lr_waiting, lock);
 117                 l_unlock(&res->lr_namespace->ns_lock);
 118                 rc = ldlm_run_ast_work(res->lr_namespace, &rpc_list);
 119                 l_lock(&res->lr_namespace->ns_lock);
 120                 if (rc == -ERESTART)
 121                         GOTO(restart, -ERESTART);
 122                 *flags |= LDLM_FL_BLOCK_GRANTED;
 123         } else {
 124                 ldlm_resource_unlink_lock(lock);
 125                 ldlm_grant_lock(lock, NULL, 0, 0);
 126         }
 127         RETURN(0);
 128 }