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|
/*
* 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/config.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.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_insert_block(struct nlm_block *block, unsigned long);
static int nlmsvc_remove_block(struct nlm_block *block);
static void nlmsvc_grant_callback(struct rpc_task *task);
/*
* The list of blocked locks to retry
*/
static struct nlm_block * nlm_blocked;
/*
* Insert a blocked lock into the global list
*/
static void
nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
{
struct nlm_block **bp, *b;
dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
if (block->b_queued)
nlmsvc_remove_block(block);
bp = &nlm_blocked;
if (when != NLM_NEVER) {
if ((when += jiffies) == NLM_NEVER)
when ++;
while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER)
bp = &b->b_next;
} else
while ((b = *bp) != 0)
bp = &b->b_next;
block->b_queued = 1;
block->b_when = when;
block->b_next = b;
*bp = block;
}
/*
* Remove a block from the global list
*/
static int
nlmsvc_remove_block(struct nlm_block *block)
{
struct nlm_block **bp, *b;
if (!block->b_queued)
return 1;
for (bp = &nlm_blocked; (b = *bp) != 0; bp = &b->b_next) {
if (b == block) {
*bp = block->b_next;
block->b_queued = 0;
return 1;
}
}
return 0;
}
/*
* Find a block for a given lock and optionally remove it from
* the list.
*/
static struct nlm_block *
nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove)
{
struct nlm_block **head, *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);
for (head = &nlm_blocked; (block = *head) != 0; head = &block->b_next) {
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(&block->b_call.a_args.cookie));
if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
if (remove) {
*head = block->b_next;
block->b_queued = 0;
}
return block;
}
}
return NULL;
}
static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
{
if(a->len != b->len)
return 0;
if(memcmp(a->data,b->data,a->len))
return 0;
return 1;
}
/*
* Find a block with a given NLM cookie.
*/
static inline struct nlm_block *
nlmsvc_find_block(struct nlm_cookie *cookie, struct sockaddr_in *sin)
{
struct nlm_block *block;
for (block = nlm_blocked; block; block = block->b_next) {
dprintk("cookie: head of blocked queue %p, block %p\n",
nlm_blocked, block);
if (nlm_cookie_match(&block->b_call.a_args.cookie,cookie)
&& nlm_cmp_addr(sin, &block->b_host->h_addr))
break;
}
return block;
}
/*
* Create a block and initialize it.
*
* Note: we explicitly set the cookie of the grant reply to that of
* the blocked lock request. The spec explicitly mentions that the client
* should _not_ rely on the callback containing the same cookie as the
* request, but (as I found out later) that's because some implementations
* do just this. Never mind the standards comittees, they support our
* logging industries.
*/
static inline struct nlm_block *
nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_lock *lock, struct nlm_cookie *cookie)
{
struct nlm_block *block;
struct nlm_host *host;
struct nlm_rqst *call;
/* Create host handle for callback */
host = nlmclnt_lookup_host(&rqstp->rq_addr,
rqstp->rq_prot, rqstp->rq_vers);
if (host == NULL)
return NULL;
/* Allocate memory for block, and initialize arguments */
if (!(block = (struct nlm_block *) kmalloc(sizeof(*block), GFP_KERNEL)))
goto failed;
memset(block, 0, sizeof(*block));
locks_init_lock(&block->b_call.a_args.lock.fl);
locks_init_lock(&block->b_call.a_res.lock.fl);
if (!nlmclnt_setgrantargs(&block->b_call, lock))
goto failed_free;
/* Set notifier function for VFS, and init args */
block->b_call.a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
block->b_call.a_args.cookie = *cookie; /* see above */
dprintk("lockd: created block %p...\n", block);
/* Create and initialize the block */
block->b_daemon = rqstp->rq_server;
block->b_host = host;
|