/*
* linux/fs/lockd/svclock.c
*
* Handling of server-side locks, mostly of the blocked variety.
* This is the ugliest part of lockd because we tread on very thin ice.
* GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
* IMNSHO introducing the grant callback into the NLM protocol was one
* of the worst ideas Sun ever had. Except maybe for the idea of doing
* NFS file locking at all.
*
* I'm trying hard to avoid race conditions by protecting most accesses
* to a file's list of blocked locks through a semaphore. The global
* list of blocked locks is not protected in this fashion however.
* Therefore, some functions (such as the RPC callback for the async grant
* call) move blocked locks towards the head of the list *while some other
* process might be traversing it*. This should not be a problem in
* practice, because this will only cause functions traversing the list
* to visit some blocks twice.
*
* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
*/
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.h>
#include <linux/kthread.h>
#define NLMDBG_FACILITY NLMDBG_SVCLOCK
#ifdef CONFIG_LOCKD_V4
#define nlm_deadlock nlm4_deadlock
#else
#define nlm_deadlock nlm_lck_denied
#endif
static void nlmsvc_release_block(struct nlm_block *block);
static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
static void nlmsvc_remove_block(struct nlm_block *block);
static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
static void nlmsvc_freegrantargs(struct nlm_rqst *call);
static const struct rpc_call_ops nlmsvc_grant_ops;
/*
* The list of blocked locks to retry
*/
static LIST_HEAD(nlm_blocked);
static DEFINE_SPINLOCK(nlm_blocked_lock);
#ifdef LOCKD_DEBUG
static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
{
/*
* We can get away with a static buffer because we're only
* called with BKL held.
*/
static char buf[2*NLM_MAXCOOKIELEN+1];
unsigned int i, len = sizeof(buf);
char *p = buf;
len--; /* allow for trailing \0 */
if (len < 3)
return "???";
for (i = 0 ; i < cookie->len ; i++) {
if (len < 2) {
strcpy(p-3, "...");
break;
}
sprintf(p, "%02x", cookie->data[i]);
p += 2;
len -= 2;
}
*p = '\0';
return buf;
}
#endif
/*
* Insert a blocked lock into the global list
*/
static void
nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
{
struct nlm_block *b;
struct list_head *pos;
dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
if (list_empty(&block->b_list)) {
kref_get(&block->b_count);
} else {
list_del_init(&block->b_list);
}
pos = &nlm_blocked;
if (when != NLM_NEVER) {
if ((when += jiffies) == NLM_NEVER)
when ++;
list_for_each(pos, &nlm_blocked) {
b = list_entry(pos, struct nlm_block, b_list);
if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
break;
}
/* On normal exit from the loop, pos == &nlm_blocked,
* so we will be adding to the end of the list - good
*/
}
list_add_tail(&block->b_list, pos);
block->b_when = when;
}
static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
{
spin_lock(&nlm_blocked_lock);
nlmsvc_insert_block_locked(block, when);
spin_unlock(&nlm_blocked_lock);
}
/*
* Remove a block from the global list
*/
static inline void
nlmsvc_remove_block(struct nlm_block *block)
{
if (!list_empty(&block->b_list)) {
spin_lock(&nlm_blocked_lock);
list_del_init(&block->b_list);
spin_unlock(&nlm_blocked_lock);
nlmsvc_release_block(block);
}
}
/*
* Find a block for a given lock
*/
static struct nlm_block *
nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
{
struct nlm_block *block;
struct file_lock *fl;
dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
file, lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end, lock->fl.fl_type);
list_for_each_entry(block, &nlm_blocked, b_list) {
fl = &block->b_call->a_args.lock.fl;
dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
block->b_file, fl->fl_pid,
(long long)fl->fl_start,
(long long)fl->fl_end, fl->fl_type,
nlmdbg_cookie2a(