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