Root/fs/lockd/clntlock.c

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();
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    if (host == NULL) {
67        lockd_down();
68        return ERR_PTR(-ENOLCK);
69    }
70
71    return host;
72}
73EXPORT_SYMBOL_GPL(nlmclnt_init);
74
75/**
76 * nlmclnt_done - Release resources allocated by nlmclnt_init()
77 * @host: nlm_host structure reserved by nlmclnt_init()
78 *
79 */
80void nlmclnt_done(struct nlm_host *host)
81{
82    nlmclnt_release_host(host);
83    lockd_down();
84}
85EXPORT_SYMBOL_GPL(nlmclnt_done);
86
87/*
88 * Queue up a lock for blocking so that the GRANTED request can see it
89 */
90struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)
91{
92    struct nlm_wait *block;
93
94    block = kmalloc(sizeof(*block), GFP_KERNEL);
95    if (block != NULL) {
96        block->b_host = host;
97        block->b_lock = fl;
98        init_waitqueue_head(&block->b_wait);
99        block->b_status = nlm_lck_blocked;
100
101        spin_lock(&nlm_blocked_lock);
102        list_add(&block->b_list, &nlm_blocked);
103        spin_unlock(&nlm_blocked_lock);
104    }
105    return block;
106}
107
108void nlmclnt_finish_block(struct nlm_wait *block)
109{
110    if (block == NULL)
111        return;
112    spin_lock(&nlm_blocked_lock);
113    list_del(&block->b_list);
114    spin_unlock(&nlm_blocked_lock);
115    kfree(block);
116}
117
118/*
119 * Block on a lock
120 */
121int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)
122{
123    long ret;
124
125    /* A borken server might ask us to block even if we didn't
126     * request it. Just say no!
127     */
128    if (block == NULL)
129        return -EAGAIN;
130
131    /* Go to sleep waiting for GRANT callback. Some servers seem
132     * to lose callbacks, however, so we're going to poll from
133     * time to time just to make sure.
134     *
135     * For now, the retry frequency is pretty high; normally
136     * a 1 minute timeout would do. See the comment before
137     * nlmclnt_lock for an explanation.
138     */
139    ret = wait_event_interruptible_timeout(block->b_wait,
140            block->b_status != nlm_lck_blocked,
141            timeout);
142    if (ret < 0)
143        return -ERESTARTSYS;
144    req->a_res.status = block->b_status;
145    return 0;
146}
147
148/*
149 * The server lockd has called us back to tell us the lock was granted
150 */
151__be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
152{
153    const struct file_lock *fl = &lock->fl;
154    const struct nfs_fh *fh = &lock->fh;
155    struct nlm_wait *block;
156    __be32 res = nlm_lck_denied;
157
158    /*
159     * Look up blocked request based on arguments.
160     * Warning: must not use cookie to match it!
161     */
162    spin_lock(&nlm_blocked_lock);
163    list_for_each_entry(block, &nlm_blocked, b_list) {
164        struct file_lock *fl_blocked = block->b_lock;
165
166        if (fl_blocked->fl_start != fl->fl_start)
167            continue;
168        if (fl_blocked->fl_end != fl->fl_end)
169            continue;
170        /*
171         * Careful! The NLM server will return the 32-bit "pid" that
172         * we put on the wire: in this case the lockowner "pid".
173         */
174        if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)
175            continue;
176        if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))
177            continue;
178        if (nfs_compare_fh(NFS_FH(fl_blocked->fl_file->f_path.dentry->d_inode) ,fh) != 0)
179            continue;
180        /* Alright, we found a lock. Set the return status
181         * and wake up the caller
182         */
183        block->b_status = nlm_granted;
184        wake_up(&block->b_wait);
185        res = nlm_granted;
186    }
187    spin_unlock(&nlm_blocked_lock);
188    return res;
189}
190
191/*
192 * The following procedures deal with the recovery of locks after a
193 * server crash.
194 */
195
196/*
197 * Reclaim all locks on server host. We do this by spawning a separate
198 * reclaimer thread.
199 */
200void
201nlmclnt_recovery(struct nlm_host *host)
202{
203    struct task_struct *task;
204
205    if (!host->h_reclaiming++) {
206        nlm_get_host(host);
207        task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
208        if (IS_ERR(task))
209            printk(KERN_ERR "lockd: unable to spawn reclaimer "
210                "thread. Locks for %s won't be reclaimed! "
211                "(%ld)\n", host->h_name, PTR_ERR(task));
212    }
213}
214
215static int
216reclaimer(void *ptr)
217{
218    struct nlm_host *host = (struct nlm_host *) ptr;
219    struct nlm_wait *block;
220    struct file_lock *fl, *next;
221    u32 nsmstate;
222
223    allow_signal(SIGKILL);
224
225    down_write(&host->h_rwsem);
226    lockd_up(); /* note: this cannot fail as lockd is already running */
227
228    dprintk("lockd: reclaiming locks for host %s\n", host->h_name);
229
230restart:
231    nsmstate = host->h_nsmstate;
232
233    /* Force a portmap getport - the peer's lockd will
234     * most likely end up on a different port.
235     */
236    host->h_nextrebind = jiffies;
237    nlm_rebind_host(host);
238
239    /* First, reclaim all locks that have been granted. */
240    list_splice_init(&host->h_granted, &host->h_reclaim);
241    list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
242        list_del_init(&fl->fl_u.nfs_fl.list);
243
244        /*
245         * sending this thread a SIGKILL will result in any unreclaimed
246         * locks being removed from the h_granted list. This means that
247         * the kernel will not attempt to reclaim them again if a new
248         * reclaimer thread is spawned for this host.
249         */
250        if (signalled())
251            continue;
252        if (nlmclnt_reclaim(host, fl) != 0)
253            continue;
254        list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
255        if (host->h_nsmstate != nsmstate) {
256            /* Argh! The server rebooted again! */
257            goto restart;
258        }
259    }
260
261    host->h_reclaiming = 0;
262    up_write(&host->h_rwsem);
263    dprintk("NLM: done reclaiming locks for host %s\n", host->h_name);
264
265    /* Now, wake up all processes that sleep on a blocked lock */
266    spin_lock(&nlm_blocked_lock);
267    list_for_each_entry(block, &nlm_blocked, b_list) {
268        if (block->b_host == host) {
269            block->b_status = nlm_lck_denied_grace_period;
270            wake_up(&block->b_wait);
271        }
272    }
273    spin_unlock(&nlm_blocked_lock);
274
275    /* Release host handle after use */
276    nlmclnt_release_host(host);
277    lockd_down();
278    return 0;
279}
280

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