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Linux/fs/lockd/clntlock.c

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  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 }
300 

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