// SPDX-License-Identifier: GPL-2.0
/*
* 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 [31mCONFIG_LOCKD_V4[0m
#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);
#if IS_ENABLED([31mCONFIG_SUNRPC_DEBUG[0m)
static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
{
/*
* We can get away with a static buffer because this is only called
* from lockd, which is single-threaded.
*/
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(&block->b_call->a_args.cookie));
if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
kref_get(&block->b_count);
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 nlm_block *block;
list_for_each_entry(block, &nlm_blocked, b_list) {
if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
goto found;
}
return NULL;
found:
dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
kref_get(&block->b_count);
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.
*
* 10 years later: I hope we can safely ignore these old and broken
* clients by now. Let's fix this so we can uniquely identify an incoming
* GRANTED_RES message by cookie, without having to rely on the client's IP
* address. --okir
*/
static struct nlm_block *
nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
struct nlm_file *file, struct nlm_lock *lock,
struct nlm_cookie *cookie)
{
struct nlm_block *block;
struct nlm_rqst *call = NULL;
call = nlm_alloc_call(host);
if (call == NULL)
return NULL;
/* Allocate memory for block, and initialize arguments */
block = kzalloc(sizeof(*block), GFP_KERNEL);
if (block == NULL)
goto failed;
kref_init(&block->b_count);
INIT_LIST_HEAD(&block->b_list);
INIT_LIST_HEAD(&block->b_flist);
if (!nlmsvc_setgrantargs(call, lock))
goto failed_free;
/* Set notifier function for VFS, and init args */
call->a_args.lock.fl.fl_flags |= FL_SLEEP;
call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
nlmclnt_next_cookie(&call->a_args.cookie);
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;
file->f_count++;
/* Add to file's list of blocks */
list_add(&block->b_flist, &file->f_blocks);
/* Set up RPC arguments for callback */
block->b_call = call;
call->a_flags = RPC_TASK_ASYNC;
call->a_block = block;
return block;
failed_free:
kfree(block);
failed:
nlmsvc_release_call(call);
return NULL;
}
/*
* Delete a block.
* It is the caller's responsibility to check whether the file
* can be closed hereafter.
*/
static int nlmsvc_unlink_block(struct nlm_block *block)
{
int status;
dprintk("lockd: unlinking block %p...\n", block);
/* Remove block from list */
status = locks_delete_block(&block->b_call->a_args.lock.fl);
nlmsvc_remove_block(block);
return status;
}
static void nlmsvc_free_block(struct kref *kref)
{
struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
struct nlm_file *file = block->b_file;
dprintk("lockd: freeing block %p...\n", block);
/* Remove block from file's list of blocks */
list_del_init(&block->b_flist);
mutex_unlock(&file->f_mutex);
nlmsvc_freegrantargs(block->b_call);
nlmsvc_release_call(block->b_call);
nlm_release_file(block->b_file);
kfree(block);
}
static void nlmsvc_release_block(struct nlm_block *block)
{
if (block != NULL)
kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
}
/*
* Loop over all blocks and delete blocks held by
* a matching host.
*/
void nlmsvc_traverse_blocks(struct nlm_host *host,
struct nlm_file *file,
nlm_host_match_fn_t match)
{
struct nlm_block *block, *next;
restart:
mutex_lock(&file->f_mutex);
list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
if (!match(block->b_host, host))
continue;
/* Do not destroy blocks that are not on
* the global retry list - why? */
if (list_empty(&block->b_list))
continue;
kref_get(&block->b_count);
mutex_unlock(&file->f_mutex);
nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
goto restart;
}
mutex_unlock(&file->f_mutex);
}
static struct nlm_lockowner *
nlmsvc_get_lockowner(struct nlm_lockowner *lockowner)
{
refcount_inc(&lockowner->count);
return lockowner;
}
static void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
{
if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
return;
list_del(&lockowner->list);
spin_unlock(&lockowner->host->h_lock);
nlmsvc_release_host(lockowner->host);
kfree(lockowner);
}
static struct nlm_lockowner *__nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
{
struct nlm_lockowner *lockowner;
list_for_each_entry(lockowner, &host->h_lockowners, list) {
if (lockowner->pid != pid)
continue;
return nlmsvc_get_lockowner(lockowner);
}
return NULL;
}
static struct nlm_lockowner *nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
{
struct nlm_lockowner *res, *new = NULL;
spin_lock(&host->h_lock);
res = __nlmsvc_find_lockowner(host, pid);
if (res == NULL) {
spin_unlock(&host->h_lock);
new = kmalloc(sizeof(*res), GFP_KERNEL);
spin_lock(&host->h_lock);
res = __nlmsvc_find_lockowner(host, pid);
if (res == NULL && new != NULL) {
res = new;
/* fs/locks.c will manage the refcount through lock_ops */
refcount_set(&new->count, 1);
new->pid = pid;
new->host = nlm_get_host(host);
list_add(&new->list, &host->h_lockowners);
new = NULL;
}
}
spin_unlock(&host->h_lock);
kfree(new);
return res;
}
void
nlmsvc_release_lockowner(struct nlm_lock *lock)
{
if (lock->fl.fl_owner)
nlmsvc_put_lockowner(lock->fl.fl_owner);
}
static void nlmsvc_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
struct nlm_lockowner *nlm_lo = (struct nlm_lockowner *)fl->fl_owner;
new->fl_owner = nlmsvc_get_lockowner(nlm_lo);
}
static void nlmsvc_locks_release_private(struct file_lock *fl)
{
nlmsvc_put_lockowner((struct nlm_lockowner *)fl->fl_owner);
}
static const struct file_lock_operations nlmsvc_lock_ops = {
.fl_copy_lock = nlmsvc_locks_copy_lock,
.fl_release_private = nlmsvc_locks_release_private,
};
void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host,
pid_t pid)
{
fl->fl_owner = nlmsvc_find_lockowner(host, pid);
if (fl->fl_owner != NULL)
fl->fl_ops = &nlmsvc_lock_ops;
}
/*
* Initialize arguments for GRANTED call. The nlm_rqst structure
* has been cleared already.
*/
static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
{
locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
call->a_args.lock.caller = utsname()->nodename;
call->a_args.lock.oh.len = lock->oh.len;
/* set default data area */
call->a_args.lock.oh.data = call->a_owner;
call->a_args.lock.svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
if (lock->oh.len > NLMCLNT_OHSIZE) {
void *data = kmalloc(lock->oh.len, GFP_KERNEL);
if (!data)
return 0;
call->a_args.lock.oh.data = (u8 *) data;
}
memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
return 1;
}
static void nlmsvc_freegrantargs(struct nlm_rqst *call)
{
if (call->a_args.lock.oh.data != call->a_owner)
kfree(call->a_args.lock.oh.data);
locks_release_private(&call->a_args.lock.fl);
}
/*
* Deferred lock request handling for non-blocking lock
*/
static __be32
nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
{
__be32 status = nlm_lck_denied_nolocks;
block->b_flags |= B_QUEUED;
nlmsvc_insert_block(block, NLM_TIMEOUT);
block->b_cache_req = &rqstp->rq_chandle;
if (rqstp->rq_chandle.defer) {
block->b_deferred_req =
rqstp->rq_chandle.defer(block->b_cache_req);
if (block->b_deferred_req != NULL)
status = nlm_drop_reply;
}
dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
block, block->b_flags, ntohl(status));
return status;
}
/*
* Attempt to establish a lock, and if it can't be granted, block it
* if required.
*/
__be32
nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_host *host, struct nlm_lock *lock, int wait,
struct nlm_cookie *cookie, int reclaim)
{
struct nlm_block *block = NULL;
int error;
__be32 ret;
dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
locks_inode(file->f_file)->i_sb->s_id,
locks_inode(file->f_file)->i_ino,
lock->fl.fl_type, lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end,
wait);
/* Lock file against concurrent access */
mutex_lock(&file->f_mutex);
/* Get existing block (in case client is busy-waiting)
* or create new block
*/
block = nlmsvc_lookup_block(file, lock);
if (block == NULL) {
block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
ret = nlm_lck_denied_nolocks;
if (block == NULL)
goto out;
lock = &block->b_call->a_args.lock;
} else
lock->fl.fl_flags &= ~FL_SLEEP;
if (block->b_flags & B_QUEUED) {
dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
block, block->b_flags);
if (block->b_granted) {
nlmsvc_unlink_block(block);
ret = nlm_granted;
goto out;
}
if (block->b_flags & B_TIMED_OUT) {
nlmsvc_unlink_block(block);
ret = nlm_lck_denied;
goto out;
}
ret = nlm_drop_reply;
goto out;
}
if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
ret = nlm_lck_denied_grace_period;
goto out;
}
if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
ret = nlm_lck_denied_grace_period;
goto out;
}
if (!wait)
lock->fl.fl_flags &= ~FL_SLEEP;
error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
lock->fl.fl_flags &= ~FL_SLEEP;
dprintk("lockd: vfs_lock_file returned %d\n", error);
switch (error) {
case 0:
ret = nlm_granted;
goto out;
case -EAGAIN:
/*
* If this is a blocking request for an
* already pending lock request then we need
* to put it back on lockd's block list
*/
if (wait)
break;
ret = nlm_lck_denied;
goto out;
case FILE_LOCK_DEFERRED:
if (wait)
break;
/* Filesystem lock operation is in progress
Add it to the queue waiting for callback */
ret = nlmsvc_defer_lock_rqst(rqstp, block);
goto out;
case -EDEADLK:
ret = nlm_deadlock;
goto out;
default: /* includes ENOLCK */
ret = nlm_lck_denied_nolocks;
goto out;
}
ret = nlm_lck_blocked;
/* Append to list of blocked */
nlmsvc_insert_block(block, NLM_NEVER);
out:
mutex_unlock(&file->f_mutex);
nlmsvc_release_block(block);
dprintk("lockd: nlmsvc_lock returned %u\n", ret);
return ret;
}
/*
* Test for presence of a conflicting lock.
*/
__be32
nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_host *host, struct nlm_lock *lock,
struct nlm_lock *conflock, struct nlm_cookie *cookie)
{
int error;
__be32 ret;
struct nlm_lockowner *test_owner;
dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
locks_inode(file->f_file)->i_sb->s_id,
locks_inode(file->f_file)->i_ino,
lock->fl.fl_type,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
if (locks_in_grace(SVC_NET(rqstp))) {
ret = nlm_lck_denied_grace_period;
goto out;
}
/* If there's a conflicting lock, remember to clean up the test lock */
test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
error = vfs_test_lock(file->f_file, &lock->fl);
if (error) {
/* We can't currently deal with deferred test requests */
if (error == FILE_LOCK_DEFERRED)
WARN_ON_ONCE(1);
ret = nlm_lck_denied_nolocks;
goto out;
}
if (lock->fl.fl_type == F_UNLCK) {
ret = nlm_granted;
goto out;
}
dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
lock->fl.fl_type, (long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
conflock->caller = "somehost"; /* FIXME */
conflock->len = strlen(conflock->caller);
conflock->oh.len = 0; /* don't return OH info */
conflock->svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
conflock->fl.fl_type = lock->fl.fl_type;
conflock->fl.fl_start = lock->fl.fl_start;
conflock->fl.fl_end = lock->fl.fl_end;
locks_release_private(&lock->fl);
/* Clean up the test lock */
lock->fl.fl_owner = NULL;
nlmsvc_put_lockowner(test_owner);
ret = nlm_lck_denied;
out:
return ret;
}
/*
* 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.
*/
__be32
nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
{
int error;
dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
locks_inode(file->f_file)->i_sb->s_id,
locks_inode(file->f_file)->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(net, file, lock);
lock->fl.fl_type = F_UNLCK;
error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
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.
*/
__be32
nlmsvc_cancel_blocked(struct net *net, 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",
locks_inode(file->f_file)->i_sb->s_id,
locks_inode(file->f_file)->i_ino,
lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
if (locks_in_grace(net))
return nlm_lck_denied_grace_period;
mutex_lock(&file->f_mutex);
block = nlmsvc_lookup_block(file, lock);
mutex_unlock(&file->f_mutex);
if (block != NULL) {
vfs_cancel_lock(block->b_file->f_file,
&block->b_call->a_args.lock.fl);
status = nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
}
return status ? nlm_lck_denied : nlm_granted;
}
/*
* This is a callback from the filesystem for VFS file lock requests.
* It will be used if lm_grant is defined and the filesystem can not
* respond to the request immediately.
* For SETLK or SETLKW request it will get the local posix lock.
* In all cases it will move the block to the head of nlm_blocked q where
* nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
* deferred rpc for GETLK and SETLK.
*/
static void
nlmsvc_update_deferred_block(struct nlm_block *block, int result)
{
block->b_flags |= B_GOT_CALLBACK;
if (result == 0)
block->b_granted = 1;
else
block->b_flags |= B_TIMED_OUT;
}
static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
{
struct nlm_block *block;
int rc = -ENOENT;
spin_lock(&nlm_blocked_lock);
list_for_each_entry(block, &nlm_blocked, b_list) {
if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
block, block->b_flags);
if (block->b_flags & B_QUEUED) {
if (block->b_flags & B_TIMED_OUT) {
rc = -ENOLCK;
break;
}
nlmsvc_update_deferred_block(block, result);
} else if (result == 0)
block->b_granted = 1;
nlmsvc_insert_block_locked(block, 0);
svc_wake_up(block->b_daemon);
rc = 0;
break;
}
}
spin_unlock(&nlm_blocked_lock);
if (rc == -ENOENT)
printk(KERN_WARNING "lockd: grant for unknown block\n");
return rc;
}
/*
* 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 *block;
dprintk("lockd: VFS unblock notification for block %p\n", fl);
spin_lock(&nlm_blocked_lock);
list_for_each_entry(block, &nlm_blocked, b_list) {
if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
nlmsvc_insert_block_locked(block, 0);
spin_unlock(&nlm_blocked_lock);
svc_wake_up(block->b_daemon);
return;
}
}
spin_unlock(&nlm_blocked_lock);
printk(KERN_WARNING "lockd: notification for unknown block!\n");
}
const struct lock_manager_operations nlmsvc_lock_operations = {
.lm_notify = nlmsvc_notify_blocked,
.lm_grant = nlmsvc_grant_deferred,
};
/*
* 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;
int error;
loff_t fl_start, fl_end;
dprintk("lockd: grant blocked lock %p\n", block);
kref_get(&block->b_count);
/* Unlink block request from list */
nlmsvc_unlink_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 */
/* vfs_lock_file() can mangle fl_start and fl_end, but we need
* them unchanged for the GRANT_MSG
*/
lock->fl.fl_flags |= FL_SLEEP;
fl_start = lock->fl.fl_start;
fl_end = lock->fl.fl_end;
error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
lock->fl.fl_flags &= ~FL_SLEEP;
lock->fl.fl_start = fl_start;
lock->fl.fl_end = fl_end;
switch (error) {
case 0:
break;
case FILE_LOCK_DEFERRED:
dprintk("lockd: lock still blocked error %d\n", error);
nlmsvc_insert_block(block, NLM_NEVER);
nlmsvc_release_block(block);
return;
default:
printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
-error, __func__);
nlmsvc_insert_block(block, 10 * HZ);
nlmsvc_release_block(block);
return;
}
callback:
/* Lock was granted by VFS. */
dprintk("lockd: GRANTing blocked lock.\n");
block->b_granted = 1;
/* keep block on the list, but don't reattempt until the RPC
* completes or the submission fails
*/
nlmsvc_insert_block(block, NLM_NEVER);
/* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
* will queue up a new one if this one times out
*/
error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
&nlmsvc_grant_ops);
/* RPC submission failed, wait a bit and retry */
if (error < 0)
nlmsvc_insert_block(block, 10 * HZ);
}
/*
* 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 = call->a_block;
unsigned long timeout;
dprintk("lockd: GRANT_MSG RPC callback\n");
spin_lock(&nlm_blocked_lock);
/* if the block is not on a list at this point then it has
* been invalidated. Don't try to requeue it.
*
* FIXME: it's possible that the block is removed from the list
* after this check but before the nlmsvc_insert_block. In that
* case it will be added back. Perhaps we need better locking
* for nlm_blocked?
*/
if (list_empty(&block->b_list))
goto out;
/* 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 {
/* Call was successful, now wait for client callback */
timeout = 60 * HZ;
}
nlmsvc_insert_block_locked(block, timeout);
svc_wake_up(block->b_daemon);
out:
spin_unlock(&nlm_blocked_lock);
}
/*
* FIXME: nlmsvc_release_block() grabs a mutex. This is not allowed for an
* .rpc_release rpc_call_op
*/
static void nlmsvc_grant_release(void *data)
{
struct nlm_rqst *call = data;
nlmsvc_release_block(call->a_block);
}
static const struct rpc_call_ops nlmsvc_grant_ops = {
.rpc_call_done = nlmsvc_grant_callback,
.rpc_release = nlmsvc_grant_release,
};
/*
* We received a GRANT_RES callback. Try to find the corresponding
* block.
*/
void
nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
{
struct nlm_block *block;
dprintk("grant_reply: looking for cookie %x, s=%d \n",
*(unsigned int *)(cookie->data), status);
if (!(block = nlmsvc_find_block(cookie)))
return;
if (status == nlm_lck_denied_grace_period) {
/* Try again in a couple of seconds */
nlmsvc_insert_block(block, 10 * HZ);
} else {
/*
* Lock is now held by client, or has been rejected.
* In both cases, the block should be removed.
*/
nlmsvc_unlink_block(block);
}
nlmsvc_release_block(block);
}
/* Helper function to handle retry of a deferred block.
* If it is a blocking lock, call grant_blocked.
* For a non-blocking lock or test lock, revisit the request.
*/
static void
retry_deferred_block(struct nlm_block *block)
{
if (!(block->b_flags & B_GOT_CALLBACK))
block->b_flags |= B_TIMED_OUT;
nlmsvc_insert_block(block, NLM_TIMEOUT);
dprintk("revisit block %p flags %d\n", block, block->b_flags);
if (block->b_deferred_req) {
block->b_deferred_req->revisit(block->b_deferred_req, 0);
block->b_deferred_req = NULL;
}
}
/*
* 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)
{
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
struct nlm_block *block;
spin_lock(&nlm_blocked_lock);
while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
if (block->b_when == NLM_NEVER)
break;
if (time_after(block->b_when, jiffies)) {
timeout = block->b_when - jiffies;
break;
}
spin_unlock(&nlm_blocked_lock);
dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
block, block->b_when);
if (block->b_flags & B_QUEUED) {
dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
block, block->b_granted, block->b_flags);
retry_deferred_block(block);
} else
nlmsvc_grant_blocked(block);
spin_lock(&nlm_blocked_lock);
}
spin_unlock(&nlm_blocked_lock);
return timeout;
}