root/fs/lockd/clntlock.c

DEFINITIONS

1. nlmclnt_init
2. nlmclnt_done
3. nlmclnt_prepare_block
4. nlmclnt_finish_block
5. nlmclnt_block
6. nlmclnt_grant
7. nlmclnt_recovery
8. reclaimer

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/fs/lockd/clntlock.c
   4  *
   5  * Lock handling for the client side NLM implementation
   6  *
   7  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
   8  */
   9 
  10 #include <linux/module.h>
  11 #include <linux/types.h>
  12 #include <linux/slab.h>
  13 #include <linux/time.h>
  14 #include <linux/nfs_fs.h>
  15 #include <linux/sunrpc/addr.h>
  16 #include <linux/sunrpc/svc.h>
  17 #include <linux/lockd/lockd.h>
  18 #include <linux/kthread.h>
  19 
  20 #define NLMDBG_FACILITY         NLMDBG_CLIENT
  21 
  22 /*
  23  * Local function prototypes
  24  */
  25 static int                      reclaimer(void *ptr);
  26 
  27 /*
  28  * The following functions handle blocking and granting from the
  29  * client perspective.
  30  */
  31 
  32 /*
  33  * This is the representation of a blocked client lock.
  34  */
  35 struct nlm_wait {
  36         struct list_head        b_list;         /* linked list */
  37         wait_queue_head_t       b_wait;         /* where to wait on */
  38         struct nlm_host *       b_host;
  39         struct file_lock *      b_lock;         /* local file lock */
  40         unsigned short          b_reclaim;      /* got to reclaim lock */
  41         __be32                  b_status;       /* grant callback status */
  42 };
  43 
  44 static LIST_HEAD(nlm_blocked);
  45 static DEFINE_SPINLOCK(nlm_blocked_lock);
  46 
  47 /**
  48  * nlmclnt_init - Set up per-NFS mount point lockd data structures
  49  * @nlm_init: pointer to arguments structure
  50  *
  51  * Returns pointer to an appropriate nlm_host struct,
  52  * or an ERR_PTR value.
  53  */
  54 struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init)
  55 {
  56         struct nlm_host *host;
  57         u32 nlm_version = (nlm_init->nfs_version == 2) ? 1 : 4;
  58         int status;
  59 
  60         status = lockd_up(nlm_init->net, nlm_init->cred);
  61         if (status < 0)
  62                 return ERR_PTR(status);
  63 
  64         host = nlmclnt_lookup_host(nlm_init->address, nlm_init->addrlen,
  65                                    nlm_init->protocol, nlm_version,
  66                                    nlm_init->hostname, nlm_init->noresvport,
  67                                    nlm_init->net, nlm_init->cred);
  68         if (host == NULL)
  69                 goto out_nohost;
  70         if (host->h_rpcclnt == NULL && nlm_bind_host(host) == NULL)
  71                 goto out_nobind;
  72 
  73         host->h_nlmclnt_ops = nlm_init->nlmclnt_ops;
  74         return host;
  75 out_nobind:
  76         nlmclnt_release_host(host);
  77 out_nohost:
  78         lockd_down(nlm_init->net);
  79         return ERR_PTR(-ENOLCK);
  80 }
  81 EXPORT_SYMBOL_GPL(nlmclnt_init);
  82 
  83 /**
  84  * nlmclnt_done - Release resources allocated by nlmclnt_init()
  85  * @host: nlm_host structure reserved by nlmclnt_init()
  86  *
  87  */
  88 void nlmclnt_done(struct nlm_host *host)
  89 {
  90         struct net *net = host->net;
  91 
  92         nlmclnt_release_host(host);
  93         lockd_down(net);
  94 }
  95 EXPORT_SYMBOL_GPL(nlmclnt_done);
  96 
  97 /*
  98  * Queue up a lock for blocking so that the GRANTED request can see it
  99  */
 100 struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)
 101 {
 102         struct nlm_wait *block;
 103 
 104         block = kmalloc(sizeof(*block), GFP_KERNEL);
 105         if (block != NULL) {
 106                 block->b_host = host;
 107                 block->b_lock = fl;
 108                 init_waitqueue_head(&block->b_wait);
 109                 block->b_status = nlm_lck_blocked;
 110 
 111                 spin_lock(&nlm_blocked_lock);
 112                 list_add(&block->b_list, &nlm_blocked);
 113                 spin_unlock(&nlm_blocked_lock);
 114         }
 115         return block;
 116 }
 117 
 118 void nlmclnt_finish_block(struct nlm_wait *block)
 119 {
 120         if (block == NULL)
 121                 return;
 122         spin_lock(&nlm_blocked_lock);
 123         list_del(&block->b_list);
 124         spin_unlock(&nlm_blocked_lock);
 125         kfree(block);
 126 }
 127 
 128 /*
 129  * Block on a lock
 130  */
 131 int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)
 132 {
 133         long ret;
 134 
 135         /* A borken server might ask us to block even if we didn't
 136          * request it. Just say no!
 137          */
 138         if (block == NULL)
 139                 return -EAGAIN;
 140 
 141         /* Go to sleep waiting for GRANT callback. Some servers seem
 142          * to lose callbacks, however, so we're going to poll from
 143          * time to time just to make sure.
 144          *
 145          * For now, the retry frequency is pretty high; normally 
 146          * a 1 minute timeout would do. See the comment before
 147          * nlmclnt_lock for an explanation.
 148          */
 149         ret = wait_event_interruptible_timeout(block->b_wait,
 150                         block->b_status != nlm_lck_blocked,
 151                         timeout);
 152         if (ret < 0)
 153                 return -ERESTARTSYS;
 154         /* Reset the lock status after a server reboot so we resend */
 155         if (block->b_status == nlm_lck_denied_grace_period)
 156                 block->b_status = nlm_lck_blocked;
 157         req->a_res.status = block->b_status;
 158         return 0;
 159 }
 160 
 161 /*
 162  * The server lockd has called us back to tell us the lock was granted
 163  */
 164 __be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
 165 {
 166         const struct file_lock *fl = &lock->fl;
 167         const struct nfs_fh *fh = &lock->fh;
 168         struct nlm_wait *block;
 169         __be32 res = nlm_lck_denied;
 170 
 171         /*
 172          * Look up blocked request based on arguments. 
 173          * Warning: must not use cookie to match it!
 174          */
 175         spin_lock(&nlm_blocked_lock);
 176         list_for_each_entry(block, &nlm_blocked, b_list) {
 177                 struct file_lock *fl_blocked = block->b_lock;
 178 
 179                 if (fl_blocked->fl_start != fl->fl_start)
 180                         continue;
 181                 if (fl_blocked->fl_end != fl->fl_end)
 182                         continue;
 183                 /*
 184                  * Careful! The NLM server will return the 32-bit "pid" that
 185                  * we put on the wire: in this case the lockowner "pid".
 186                  */
 187                 if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)
 188                         continue;
 189                 if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))
 190                         continue;
 191                 if (nfs_compare_fh(NFS_FH(locks_inode(fl_blocked->fl_file)), fh) != 0)
 192                         continue;
 193                 /* Alright, we found a lock. Set the return status
 194                  * and wake up the caller
 195                  */
 196                 block->b_status = nlm_granted;
 197                 wake_up(&block->b_wait);
 198                 res = nlm_granted;
 199         }
 200         spin_unlock(&nlm_blocked_lock);
 201         return res;
 202 }
 203 
 204 /*
 205  * The following procedures deal with the recovery of locks after a
 206  * server crash.
 207  */
 208 
 209 /*
 210  * Reclaim all locks on server host. We do this by spawning a separate
 211  * reclaimer thread.
 212  */
 213 void
 214 nlmclnt_recovery(struct nlm_host *host)
 215 {
 216         struct task_struct *task;
 217 
 218         if (!host->h_reclaiming++) {
 219                 nlm_get_host(host);
 220                 task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
 221                 if (IS_ERR(task))
 222                         printk(KERN_ERR "lockd: unable to spawn reclaimer "
 223                                 "thread. Locks for %s won't be reclaimed! "
 224                                 "(%ld)\n", host->h_name, PTR_ERR(task));
 225         }
 226 }
 227 
 228 static int
 229 reclaimer(void *ptr)
 230 {
 231         struct nlm_host   *host = (struct nlm_host *) ptr;
 232         struct nlm_wait   *block;
 233         struct nlm_rqst   *req;
 234         struct file_lock *fl, *next;
 235         u32 nsmstate;
 236         struct net *net = host->net;
 237 
 238         req = kmalloc(sizeof(*req), GFP_KERNEL);
 239         if (!req)
 240                 return 0;
 241 
 242         allow_signal(SIGKILL);
 243 
 244         down_write(&host->h_rwsem);
 245         lockd_up(net, NULL);    /* note: this cannot fail as lockd is already running */
 246 
 247         dprintk("lockd: reclaiming locks for host %s\n", host->h_name);
 248 
 249 restart:
 250         nsmstate = host->h_nsmstate;
 251 
 252         /* Force a portmap getport - the peer's lockd will
 253          * most likely end up on a different port.
 254          */
 255         host->h_nextrebind = jiffies;
 256         nlm_rebind_host(host);
 257 
 258         /* First, reclaim all locks that have been granted. */
 259         list_splice_init(&host->h_granted, &host->h_reclaim);
 260         list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
 261                 list_del_init(&fl->fl_u.nfs_fl.list);
 262 
 263                 /*
 264                  * sending this thread a SIGKILL will result in any unreclaimed
 265                  * locks being removed from the h_granted list. This means that
 266                  * the kernel will not attempt to reclaim them again if a new
 267                  * reclaimer thread is spawned for this host.
 268                  */
 269                 if (signalled())
 270                         continue;
 271                 if (nlmclnt_reclaim(host, fl, req) != 0)
 272                         continue;
 273                 list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
 274                 if (host->h_nsmstate != nsmstate) {
 275                         /* Argh! The server rebooted again! */
 276                         goto restart;
 277                 }
 278         }
 279 
 280         host->h_reclaiming = 0;
 281         up_write(&host->h_rwsem);
 282         dprintk("NLM: done reclaiming locks for host %s\n", host->h_name);
 283 
 284         /* Now, wake up all processes that sleep on a blocked lock */
 285         spin_lock(&nlm_blocked_lock);
 286         list_for_each_entry(block, &nlm_blocked, b_list) {
 287                 if (block->b_host == host) {
 288                         block->b_status = nlm_lck_denied_grace_period;
 289                         wake_up(&block->b_wait);
 290                 }
 291         }
 292         spin_unlock(&nlm_blocked_lock);
 293 
 294         /* Release host handle after use */
 295         nlmclnt_release_host(host);
 296         lockd_down(net);
 297         kfree(req);
 298         return 0;
 299 }