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 #include <linux/lm_interface.h>
  20
  21 struct lmh_wrapper {
  22         struct list_head lw_list;
  23         const struct lm_lockops *lw_ops;
  24 };
  25
  26 static int nolock_mount(char *table_name, char *host_data,
  27                         lm_callback_t cb, void *cb_data,
  28                         unsigned int min_lvb_size, int flags,
  29                         struct lm_lockstruct *lockstruct,
  30                         struct kobject *fskobj);
  31
  32 /* List of registered low-level locking protocols.  A file system selects one
  33    of them by name at mount time, e.g. lock_nolock, lock_dlm. */
  34
  35 static const struct lm_lockops nolock_ops = {
  36         .lm_proto_name = "lock_nolock",
  37         .lm_mount = nolock_mount,
  38 };
  39
  40 static struct lmh_wrapper nolock_proto  = {
  41         .lw_list = LIST_HEAD_INIT(nolock_proto.lw_list),
  42         .lw_ops = &nolock_ops,
  43 };
  44
  45 static LIST_HEAD(lmh_list);
  46 static DEFINE_MUTEX(lmh_lock);
  47
  48 static int nolock_mount(char *table_name, char *host_data,
  49                         lm_callback_t cb, void *cb_data,
  50                         unsigned int min_lvb_size, int flags,
  51                         struct lm_lockstruct *lockstruct,
  52                         struct kobject *fskobj)
  53 {
  54         char *c;
  55         unsigned int jid;
  56
  57         c = strstr(host_data, "jid=");
  58         if (!c)
  59                 jid = 0;
  60         else {
  61                 c += 4;
  62                 sscanf(c, "%u", &jid);
  63         }
  64
  65         lockstruct->ls_jid = jid;
  66         lockstruct->ls_first = 1;
  67         lockstruct->ls_lvb_size = min_lvb_size;
  68         lockstruct->ls_ops = &nolock_ops;
  69         lockstruct->ls_flags = LM_LSFLAG_LOCAL;
  70
  71         return 0;
  72 }
  73
  74 /**
  75  * gfs2_register_lockproto - Register a low-level locking protocol
  76  * @proto: the protocol definition
  77  *
  78  * Returns: 0 on success, -EXXX on failure
  79  */
  80
  81 int gfs2_register_lockproto(const struct lm_lockops *proto)
  82 {
  83         struct lmh_wrapper *lw;
  84
  85         mutex_lock(&lmh_lock);
  86
  87         list_for_each_entry(lw, &lmh_list, lw_list) {
  88                 if (!strcmp(lw->lw_ops->lm_proto_name, proto->lm_proto_name)) {
  89                         mutex_unlock(&lmh_lock);
  90                         printk(KERN_INFO "GFS2: protocol %s already exists\n",
  91                                proto->lm_proto_name);
  92                         return -EEXIST;
  93                 }
  94         }
  95
  96         lw = kzalloc(sizeof(struct lmh_wrapper), GFP_KERNEL);
  97         if (!lw) {
  98                 mutex_unlock(&lmh_lock);
  99                 return -ENOMEM;
 100         }
 101
 102         lw->lw_ops = proto;
 103         list_add(&lw->lw_list, &lmh_list);
 104
 105         mutex_unlock(&lmh_lock);
 106
 107         return 0;
 108 }
 109
 110 /**
 111  * gfs2_unregister_lockproto - Unregister a low-level locking protocol
 112  * @proto: the protocol definition
 113  *
 114  */
 115
 116 void gfs2_unregister_lockproto(const struct lm_lockops *proto)
 117 {
 118         struct lmh_wrapper *lw;
 119
 120         mutex_lock(&lmh_lock);
 121
 122         list_for_each_entry(lw, &lmh_list, lw_list) {
 123                 if (!strcmp(lw->lw_ops->lm_proto_name, proto->lm_proto_name)) {
 124                         list_del(&lw->lw_list);
 125                         mutex_unlock(&lmh_lock);
 126                         kfree(lw);
 127                         return;
 128                 }
 129         }
 130
 131         mutex_unlock(&lmh_lock);
 132
 133         printk(KERN_WARNING "GFS2: can't unregister lock protocol %s\n",
 134                proto->lm_proto_name);
 135 }
 136
 137 /**
 138  * gfs2_mount_lockproto - Mount a lock protocol
 139  * @proto_name - the name of the protocol
 140  * @table_name - the name of the lock space
 141  * @host_data - data specific to this host
 142  * @cb - the callback to the code using the lock module
 143  * @sdp - The GFS2 superblock
 144  * @min_lvb_size - the mininum LVB size that the caller can deal with
 145  * @flags - LM_MFLAG_*
 146  * @lockstruct - a structure returned describing the mount
 147  *
 148  * Returns: 0 on success, -EXXX on failure
 149  */
 150
 151 int gfs2_mount_lockproto(char *proto_name, char *table_name, char *host_data,
 152                          lm_callback_t cb, void *cb_data,
 153                          unsigned int min_lvb_size, int flags,
 154                          struct lm_lockstruct *lockstruct,
 155                          struct kobject *fskobj)
 156 {
 157         struct lmh_wrapper *lw = NULL;
 158         int try = 0;
 159         int error, found;
 160
 161
 162 retry:
 163         mutex_lock(&lmh_lock);
 164
 165         if (list_empty(&nolock_proto.lw_list))
 166                 list_add(&nolock_proto.lw_list, &lmh_list);
 167
 168         found = 0;
 169         list_for_each_entry(lw, &lmh_list, lw_list) {
 170                 if (!strcmp(lw->lw_ops->lm_proto_name, proto_name)) {
 171                         found = 1;
 172                         break;
 173                 }
 174         }
 175
 176         if (!found) {
 177                 if (!try && capable(CAP_SYS_MODULE)) {
 178                         try = 1;
 179                         mutex_unlock(&lmh_lock);
 180                         request_module(proto_name);
 181                         goto retry;
 182                 }
 183                 printk(KERN_INFO "GFS2: can't find protocol %s\n", proto_name);
 184                 error = -ENOENT;
 185                 goto out;
 186         }
 187
 188         if (lw->lw_ops->lm_owner &&
 189             !try_module_get(lw->lw_ops->lm_owner)) {
 190                 try = 0;
 191                 mutex_unlock(&lmh_lock);
 192                 msleep(1000);
 193                 goto retry;
 194         }
 195
 196         error = lw->lw_ops->lm_mount(table_name, host_data, cb, cb_data,
 197                                      min_lvb_size, flags, lockstruct, fskobj);
 198         if (error)
 199                 module_put(lw->lw_ops->lm_owner);
 200 out:
 201         mutex_unlock(&lmh_lock);
 202         return error;
 203 }
 204
 205 void gfs2_unmount_lockproto(struct lm_lockstruct *lockstruct)
 206 {
 207         mutex_lock(&lmh_lock);
 208         if (lockstruct->ls_ops->lm_unmount)
 209                 lockstruct->ls_ops->lm_unmount(lockstruct->ls_lockspace);
 210         if (lockstruct->ls_ops->lm_owner)
 211                 module_put(lockstruct->ls_ops->lm_owner);
 212         mutex_unlock(&lmh_lock);
 213 }
 214
 215 /**
 216  * gfs2_withdraw_lockproto - abnormally unmount a lock module
 217  * @lockstruct: the lockstruct passed into mount
 218  *
 219  */
 220
 221 void gfs2_withdraw_lockproto(struct lm_lockstruct *lockstruct)
 222 {
 223         mutex_lock(&lmh_lock);
 224         lockstruct->ls_ops->lm_withdraw(lockstruct->ls_lockspace);
 225         if (lockstruct->ls_ops->lm_owner)
 226                 module_put(lockstruct->ls_ops->lm_owner);
 227         mutex_unlock(&lmh_lock);
 228 }
 229
 230 EXPORT_SYMBOL_GPL(gfs2_register_lockproto);
 231 EXPORT_SYMBOL_GPL(gfs2_unregister_lockproto);
 232