linux/fs/lockd/svclock.c
J. Bruce Fields 64a318ee2a NLM: Further cancel fixes
If the server receives an NLM cancel call and finds no waiting lock to
 cancel, then chances are the lock has already been applied, and the client
 just hadn't yet processed the NLM granted callback before it sent the
 cancel.

 The Open Group text, for example, perimts a server to return either success
 (LCK_GRANTED) or failure (LCK_DENIED) in this case.  But returning an error
 seems more helpful; the client may be able to use it to recognize that a
 race has occurred and to recover from the race.

 So, modify the relevant functions to return an error in this case.

 Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2006-01-06 14:58:54 -05:00

689 lines
19 KiB
C

/*
* 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 const struct rpc_call_ops nlmsvc_grant_ops;
/*
* 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;
block->b_file = file;
/* Add to file's list of blocks */
block->b_fnext = file->f_blocks;
file->f_blocks = block;
/* Set up RPC arguments for callback */
call = &block->b_call;
call->a_host = host;
call->a_flags = RPC_TASK_ASYNC;
return block;
failed_free:
kfree(block);
failed:
nlm_release_host(host);
return NULL;
}
/*
* Delete a block. If the lock was cancelled or the grant callback
* failed, unlock is set to 1.
* It is the caller's responsibility to check whether the file
* can be closed hereafter.
*/
static int
nlmsvc_delete_block(struct nlm_block *block, int unlock)
{
struct file_lock *fl = &block->b_call.a_args.lock.fl;
struct nlm_file *file = block->b_file;
struct nlm_block **bp;
int status = 0;
dprintk("lockd: deleting block %p...\n", block);
/* Remove block from list */
nlmsvc_remove_block(block);
if (unlock)
status = posix_unblock_lock(file->f_file, fl);
/* If the block is in the middle of a GRANT callback,
* don't kill it yet. */
if (block->b_incall) {
nlmsvc_insert_block(block, NLM_NEVER);
block->b_done = 1;
return status;
}
/* Remove block from file's list of blocks */
for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
if (*bp == block) {
*bp = block->b_fnext;
break;
}
}
if (block->b_host)
nlm_release_host(block->b_host);
nlmclnt_freegrantargs(&block->b_call);
kfree(block);
return status;
}
/*
* Loop over all blocks and perform the action specified.
* (NLM_ACT_CHECK handled by nlmsvc_inspect_file).
*/
int
nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
{
struct nlm_block *block, *next;
/* XXX: Will everything get cleaned up if we don't unlock here? */
down(&file->f_sema);
for (block = file->f_blocks; block; block = next) {
next = block->b_fnext;
if (action == NLM_ACT_MARK)
block->b_host->h_inuse = 1;
else if (action == NLM_ACT_UNLOCK) {
if (host == NULL || host == block->b_host)
nlmsvc_delete_block(block, 1);
}
}
up(&file->f_sema);
return 0;
}
/*
* Attempt to establish a lock, and if it can't be granted, block it
* if required.
*/
u32
nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
{
struct file_lock *conflock;
struct nlm_block *block;
int error;
dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
file->f_file->f_dentry->d_inode->i_sb->s_id,
file->f_file->f_dentry->d_inode->i_ino,
lock->fl.fl_type, lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end,
wait);
/* Get existing block (in case client is busy-waiting) */
block = nlmsvc_lookup_block(file, lock, 0);
lock->fl.fl_flags |= FL_LOCKD;
again:
/* Lock file against concurrent access */
down(&file->f_sema);
if (!(conflock = posix_test_lock(file->f_file, &lock->fl))) {
error = posix_lock_file(file->f_file, &lock->fl);
if (block)
nlmsvc_delete_block(block, 0);
up(&file->f_sema);
dprintk("lockd: posix_lock_file returned %d\n", -error);
switch(-error) {
case 0:
return nlm_granted;
case EDEADLK:
return nlm_deadlock;
case EAGAIN:
return nlm_lck_denied;
default: /* includes ENOLCK */
return nlm_lck_denied_nolocks;
}
}
if (!wait) {
up(&file->f_sema);
return nlm_lck_denied;
}
if (posix_locks_deadlock(&lock->fl, conflock)) {
up(&file->f_sema);
return nlm_deadlock;
}
/* If we don't have a block, create and initialize it. Then
* retry because we may have slept in kmalloc. */
/* We have to release f_sema as nlmsvc_create_block may try to
* to claim it while doing host garbage collection */
if (block == NULL) {
up(&file->f_sema);
dprintk("lockd: blocking on this lock (allocating).\n");
if (!(block = nlmsvc_create_block(rqstp, file, lock, cookie)))
return nlm_lck_denied_nolocks;
goto again;
}
/* Append to list of blocked */
nlmsvc_insert_block(block, NLM_NEVER);
if (list_empty(&block->b_call.a_args.lock.fl.fl_block)) {
/* Now add block to block list of the conflicting lock
if we haven't done so. */
dprintk("lockd: blocking on this lock.\n");
posix_block_lock(conflock, &block->b_call.a_args.lock.fl);
}
up(&file->f_sema);
return nlm_lck_blocked;
}
/*
* Test for presence of a conflicting lock.
*/
u32
nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
struct nlm_lock *conflock)
{
struct file_lock *fl;
dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
file->f_file->f_dentry->d_inode->i_sb->s_id,
file->f_file->f_dentry->d_inode->i_ino,
lock->fl.fl_type,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
if ((fl = posix_test_lock(file->f_file, &lock->fl)) != NULL) {
dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
fl->fl_type, (long long)fl->fl_start,
(long long)fl->fl_end);
conflock->caller = "somehost"; /* FIXME */
conflock->oh.len = 0; /* don't return OH info */
conflock->fl = *fl;
return nlm_lck_denied;
}
return nlm_granted;
}
/*
* Remove a lock.
* This implies a CANCEL call: We send a GRANT_MSG, the client replies
* with a GRANT_RES call which gets lost, and calls UNLOCK immediately
* afterwards. In this case the block will still be there, and hence
* must be removed.
*/
u32
nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
{
int error;
dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
file->f_file->f_dentry->d_inode->i_sb->s_id,
file->f_file->f_dentry->d_inode->i_ino,
lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
/* First, cancel any lock that might be there */
nlmsvc_cancel_blocked(file, lock);
lock->fl.fl_type = F_UNLCK;
error = posix_lock_file(file->f_file, &lock->fl);
return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
}
/*
* Cancel a previously blocked request.
*
* A cancel request always overrides any grant that may currently
* be in progress.
* The calling procedure must check whether the file can be closed.
*/
u32
nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
{
struct nlm_block *block;
int status = 0;
dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
file->f_file->f_dentry->d_inode->i_sb->s_id,
file->f_file->f_dentry->d_inode->i_ino,
lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
down(&file->f_sema);
if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL)
status = nlmsvc_delete_block(block, 1);
up(&file->f_sema);
return status ? nlm_lck_denied : nlm_granted;
}
/*
* Unblock a blocked lock request. This is a callback invoked from the
* VFS layer when a lock on which we blocked is removed.
*
* This function doesn't grant the blocked lock instantly, but rather moves
* the block to the head of nlm_blocked where it can be picked up by lockd.
*/
static void
nlmsvc_notify_blocked(struct file_lock *fl)
{
struct nlm_block **bp, *block;
dprintk("lockd: VFS unblock notification for block %p\n", fl);
for (bp = &nlm_blocked; (block = *bp) != 0; bp = &block->b_next) {
if (nlm_compare_locks(&block->b_call.a_args.lock.fl, fl)) {
nlmsvc_insert_block(block, 0);
svc_wake_up(block->b_daemon);
return;
}
}
printk(KERN_WARNING "lockd: notification for unknown block!\n");
}
static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
}
struct lock_manager_operations nlmsvc_lock_operations = {
.fl_compare_owner = nlmsvc_same_owner,
.fl_notify = nlmsvc_notify_blocked,
};
/*
* Try to claim a lock that was previously blocked.
*
* Note that we use both the RPC_GRANTED_MSG call _and_ an async
* RPC thread when notifying the client. This seems like overkill...
* Here's why:
* - we don't want to use a synchronous RPC thread, otherwise
* we might find ourselves hanging on a dead portmapper.
* - Some lockd implementations (e.g. HP) don't react to
* RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
*/
static void
nlmsvc_grant_blocked(struct nlm_block *block)
{
struct nlm_file *file = block->b_file;
struct nlm_lock *lock = &block->b_call.a_args.lock;
struct file_lock *conflock;
int error;
dprintk("lockd: grant blocked lock %p\n", block);
/* First thing is lock the file */
down(&file->f_sema);
/* Unlink block request from list */
nlmsvc_remove_block(block);
/* If b_granted is true this means we've been here before.
* Just retry the grant callback, possibly refreshing the RPC
* binding */
if (block->b_granted) {
nlm_rebind_host(block->b_host);
goto callback;
}
/* Try the lock operation again */
if ((conflock = posix_test_lock(file->f_file, &lock->fl)) != NULL) {
/* Bummer, we blocked again */
dprintk("lockd: lock still blocked\n");
nlmsvc_insert_block(block, NLM_NEVER);
posix_block_lock(conflock, &lock->fl);
up(&file->f_sema);
return;
}
/* Alright, no conflicting lock. Now lock it for real. If the
* following yields an error, this is most probably due to low
* memory. Retry the lock in a few seconds.
*/
if ((error = posix_lock_file(file->f_file, &lock->fl)) < 0) {
printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
-error, __FUNCTION__);
nlmsvc_insert_block(block, 10 * HZ);
up(&file->f_sema);
return;
}
callback:
/* Lock was granted by VFS. */
dprintk("lockd: GRANTing blocked lock.\n");
block->b_granted = 1;
block->b_incall = 1;
/* Schedule next grant callback in 30 seconds */
nlmsvc_insert_block(block, 30 * HZ);
/* Call the client */
nlm_get_host(block->b_call.a_host);
if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
&nlmsvc_grant_ops) < 0)
nlm_release_host(block->b_call.a_host);
up(&file->f_sema);
}
/*
* This is the callback from the RPC layer when the NLM_GRANTED_MSG
* RPC call has succeeded or timed out.
* Like all RPC callbacks, it is invoked by the rpciod process, so it
* better not sleep. Therefore, we put the blocked lock on the nlm_blocked
* chain once more in order to have it removed by lockd itself (which can
* then sleep on the file semaphore without disrupting e.g. the nfs client).
*/
static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
{
struct nlm_rqst *call = data;
struct nlm_block *block;
unsigned long timeout;
struct sockaddr_in *peer_addr = RPC_PEERADDR(task->tk_client);
dprintk("lockd: GRANT_MSG RPC callback\n");
dprintk("callback: looking for cookie %s, host (%u.%u.%u.%u)\n",
nlmdbg_cookie2a(&call->a_args.cookie),
NIPQUAD(peer_addr->sin_addr.s_addr));
if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) {
dprintk("lockd: no block for cookie %s, host (%u.%u.%u.%u)\n",
nlmdbg_cookie2a(&call->a_args.cookie),
NIPQUAD(peer_addr->sin_addr.s_addr));
return;
}
/* Technically, we should down the file semaphore here. Since we
* move the block towards the head of the queue only, no harm
* can be done, though. */
if (task->tk_status < 0) {
/* RPC error: Re-insert for retransmission */
timeout = 10 * HZ;
} else if (block->b_done) {
/* Block already removed, kill it for real */
timeout = 0;
} else {
/* Call was successful, now wait for client callback */
timeout = 60 * HZ;
}
nlmsvc_insert_block(block, timeout);
svc_wake_up(block->b_daemon);
block->b_incall = 0;
nlm_release_host(call->a_host);
}
static const struct rpc_call_ops nlmsvc_grant_ops = {
.rpc_call_done = nlmsvc_grant_callback,
};
/*
* We received a GRANT_RES callback. Try to find the corresponding
* block.
*/
void
nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status)
{
struct nlm_block *block;
struct nlm_file *file;
dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n",
*(unsigned int *)(cookie->data),
ntohl(rqstp->rq_addr.sin_addr.s_addr), status);
if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr)))
return;
file = block->b_file;
file->f_count++;
down(&file->f_sema);
block = nlmsvc_find_block(cookie, &rqstp->rq_addr);
if (block) {
if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
/* Try again in a couple of seconds */
nlmsvc_insert_block(block, 10 * HZ);
up(&file->f_sema);
} else {
/* Lock is now held by client, or has been rejected.
* In both cases, the block should be removed. */
up(&file->f_sema);
if (status == NLM_LCK_GRANTED)
nlmsvc_delete_block(block, 0);
else
nlmsvc_delete_block(block, 1);
}
}
nlm_release_file(file);
}
/*
* Retry all blocked locks that have been notified. This is where lockd
* picks up locks that can be granted, or grant notifications that must
* be retransmitted.
*/
unsigned long
nlmsvc_retry_blocked(void)
{
struct nlm_block *block;
dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
nlm_blocked,
nlm_blocked? nlm_blocked->b_when : 0);
while ((block = nlm_blocked) != 0) {
if (block->b_when == NLM_NEVER)
break;
if (time_after(block->b_when,jiffies))
break;
dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
block, block->b_when, block->b_done);
if (block->b_done)
nlmsvc_delete_block(block, 0);
else
nlmsvc_grant_blocked(block);
}
if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
return (block->b_when - jiffies);
return MAX_SCHEDULE_TIMEOUT;
}