fs/gfs2/locking.c

   1 /*
   2  * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   3  * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
   4  *
   5  * This copyrighted material is made available to anyone wishing to use,
   6  * modify, copy, or redistribute it subject to the terms and conditions
   7  * of the GNU General Public License version 2.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/string.h>
  13 #include <linux/slab.h>
  14 #include <linux/wait.h>
  15 #include <linux/sched.h>
  16 #include <linux/kmod.h>
  17 #include <linux/fs.h>
  18 #include <linux/delay.h>
  19
  20 #include "lm_interface.h"
  21
  22 struct lmh_wrapper {
  23         struct list_head lw_list;
  24         struct lm_lockops *lw_ops;
  25 };
  26
  27 /* List of registered low-level locking protocols.  A file system selects one
  28    of them by name at mount time, e.g. lock_nolock, lock_dlm. */
  29
  30 static struct list_head lmh_list;
  31 static struct mutex lmh_lock;
  32
  33 /**
  34  * gfs2_register_lockproto - Register a low-level locking protocol
  35  * @proto: the protocol definition
  36  *
  37  * Returns: 0 on success, -EXXX on failure
  38  */
  39
  40 int gfs2_register_lockproto(struct lm_lockops *proto)
  41 {
  42         struct lmh_wrapper *lw;
  43
  44         mutex_lock(&lmh_lock);
  45
  46         list_for_each_entry(lw, &lmh_list, lw_list) {
  47                 if (!strcmp(lw->lw_ops->lm_proto_name, proto->lm_proto_name)) {
  48                         mutex_unlock(&lmh_lock);
  49                         printk(KERN_INFO "GFS2: protocol %s already exists\n",
  50                                proto->lm_proto_name);
  51                         return -EEXIST;
  52                 }
  53         }
  54
  55         lw = kzalloc(sizeof(struct lmh_wrapper), GFP_KERNEL);
  56         if (!lw) {
  57                 mutex_unlock(&lmh_lock);
  58                 return -ENOMEM;
  59         }
  60
  61         lw->lw_ops = proto;
  62         list_add(&lw->lw_list, &lmh_list);
  63
  64         mutex_unlock(&lmh_lock);
  65
  66         return 0;
  67 }
  68
  69 /**
  70  * gfs2_unregister_lockproto - Unregister a low-level locking protocol
  71  * @proto: the protocol definition
  72  *
  73  */
  74
  75 void gfs2_unregister_lockproto(struct lm_lockops *proto)
  76 {
  77         struct lmh_wrapper *lw;
  78
  79         mutex_lock(&lmh_lock);
  80
  81         list_for_each_entry(lw, &lmh_list, lw_list) {
  82                 if (!strcmp(lw->lw_ops->lm_proto_name, proto->lm_proto_name)) {
  83                         list_del(&lw->lw_list);
  84                         mutex_unlock(&lmh_lock);
  85                         kfree(lw);
  86                         return;
  87                 }
  88         }
  89
  90         mutex_unlock(&lmh_lock);
  91
  92         printk(KERN_WARNING "GFS2: can't unregister lock protocol %s\n",
  93                proto->lm_proto_name);
  94 }
  95
  96 /**
  97  * gfs2_mount_lockproto - Mount a lock protocol
  98  * @proto_name - the name of the protocol
  99  * @table_name - the name of the lock space
 100  * @host_data - data specific to this host
 101  * @cb - the callback to the code using the lock module
 102  * @fsdata - data to pass back with the callback
 103  * @min_lvb_size - the mininum LVB size that the caller can deal with
 104  * @flags - LM_MFLAG_*
 105  * @lockstruct - a structure returned describing the mount
 106  *
 107  * Returns: 0 on success, -EXXX on failure
 108  */
 109
 110 int gfs2_mount_lockproto(char *proto_name, char *table_name, char *host_data,
 111                          lm_callback_t cb, lm_fsdata_t *fsdata,
 112                          unsigned int min_lvb_size, int flags,
 113                          struct lm_lockstruct *lockstruct,
 114                          struct kobject *fskobj)
 115 {
 116         struct lmh_wrapper *lw = NULL;
 117         int try = 0;
 118         int error, found;
 119
 120 retry:
 121         mutex_lock(&lmh_lock);
 122
 123         found = 0;
 124         list_for_each_entry(lw, &lmh_list, lw_list) {
 125                 if (!strcmp(lw->lw_ops->lm_proto_name, proto_name)) {
 126                         found = 1;
 127                         break;
 128                 }
 129         }
 130
 131         if (!found) {
 132                 if (!try && capable(CAP_SYS_MODULE)) {
 133                         try = 1;
 134                         mutex_unlock(&lmh_lock);
 135                         request_module(proto_name);
 136                         goto retry;
 137                 }
 138                 printk(KERN_INFO "GFS2: can't find protocol %s\n", proto_name);
 139                 error = -ENOENT;
 140                 goto out;
 141         }
 142
 143         if (!try_module_get(lw->lw_ops->lm_owner)) {
 144                 try = 0;
 145                 mutex_unlock(&lmh_lock);
 146                 msleep(1000);
 147                 goto retry;
 148         }
 149
 150         error = lw->lw_ops->lm_mount(table_name, host_data, cb, fsdata,
 151                                      min_lvb_size, flags, lockstruct, fskobj);
 152         if (error)
 153                 module_put(lw->lw_ops->lm_owner);
 154 out:
 155         mutex_unlock(&lmh_lock);
 156         return error;
 157 }
 158
 159 void gfs2_unmount_lockproto(struct lm_lockstruct *lockstruct)
 160 {
 161         mutex_lock(&lmh_lock);
 162         lockstruct->ls_ops->lm_unmount(lockstruct->ls_lockspace);
 163         if (lockstruct->ls_ops->lm_owner)
 164                 module_put(lockstruct->ls_ops->lm_owner);
 165         mutex_unlock(&lmh_lock);
 166 }
 167
 168 /**
 169  * gfs2_withdraw_lockproto - abnormally unmount a lock module
 170  * @lockstruct: the lockstruct passed into mount
 171  *
 172  */
 173
 174 void gfs2_withdraw_lockproto(struct lm_lockstruct *lockstruct)
 175 {
 176         mutex_lock(&lmh_lock);
 177         lockstruct->ls_ops->lm_withdraw(lockstruct->ls_lockspace);
 178         if (lockstruct->ls_ops->lm_owner)
 179                 module_put(lockstruct->ls_ops->lm_owner);
 180         mutex_unlock(&lmh_lock);
 181 }
 182
 183 void __init gfs2_init_lmh(void)
 184 {
 185         mutex_init(&lmh_lock);
 186         INIT_LIST_HEAD(&lmh_list);
 187 }
 188
 189 EXPORT_SYMBOL_GPL(gfs2_register_lockproto);
 190 EXPORT_SYMBOL_GPL(gfs2_unregister_lockproto);
 191