linux-stable/fs/lockd/svclock.c
NeilBrown 2ec197db1a lockd: send correct lock when granting a delayed lock.
If an NFS client attempts to get a lock (using NLM) and the lock is
not available, the server will remember the request and when the lock
becomes available it will send a GRANT request to the client to
provide the lock.

If the client already held an adjacent lock, the GRANT callback will
report the union of the existing and new locks, which can confuse the
client.

This happens because __posix_lock_file (called by vfs_lock_file)
updates the passed-in file_lock structure when adjacent or
over-lapping locks are found.

To avoid this problem we take a copy of the two fields that can
be changed (fl_start and fl_end) before the call and restore them
afterwards.
An alternate would be to allocate a 'struct file_lock', initialise it,
use locks_copy_lock() to take a copy, then locks_release_private()
after the vfs_lock_file() call.  But that is a lot more work.

Reported-by: Olaf Kirch <okir@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

--
v1 had a couple of issues (large on-stack struct and didn't really work properly).
This version is much better tested.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2014-02-13 14:55:02 -05:00

987 lines
26 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/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(&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;
block->b_fl = NULL;
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 = posix_unblock_lock(&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->b_fl);
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);
}
/*
* 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 = lock->fl.fl_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",
file_inode(file->f_file)->i_sb->s_id,
file_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)
{
struct nlm_block *block = NULL;
int error;
__be32 ret;
dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
file_inode(file->f_file)->i_sb->s_id,
file_inode(file->f_file)->i_ino,
lock->fl.fl_type,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
/* Get existing block (in case client is busy-waiting) */
block = nlmsvc_lookup_block(file, lock);
if (block == NULL) {
struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
if (conf == NULL)
return nlm_granted;
block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
if (block == NULL) {
kfree(conf);
return nlm_granted;
}
block->b_fl = conf;
}
if (block->b_flags & B_QUEUED) {
dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
block, block->b_flags, block->b_fl);
if (block->b_flags & B_TIMED_OUT) {
nlmsvc_unlink_block(block);
ret = nlm_lck_denied;
goto out;
}
if (block->b_flags & B_GOT_CALLBACK) {
nlmsvc_unlink_block(block);
if (block->b_fl != NULL
&& block->b_fl->fl_type != F_UNLCK) {
lock->fl = *block->b_fl;
goto conf_lock;
} else {
ret = nlm_granted;
goto out;
}
}
ret = nlm_drop_reply;
goto out;
}
if (locks_in_grace(SVC_NET(rqstp))) {
ret = nlm_lck_denied_grace_period;
goto out;
}
error = vfs_test_lock(file->f_file, &lock->fl);
if (error == FILE_LOCK_DEFERRED) {
ret = nlmsvc_defer_lock_rqst(rqstp, block);
goto out;
}
if (error) {
ret = nlm_lck_denied_nolocks;
goto out;
}
if (lock->fl.fl_type == F_UNLCK) {
ret = nlm_granted;
goto out;
}
conf_lock:
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 = lock->fl.fl_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;
ret = nlm_lck_denied;
out:
if (block)
nlmsvc_release_block(block);
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",
file_inode(file->f_file)->i_sb->s_id,
file_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",
file_inode(file->f_file)->i_sb->s_id,
file_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 GETLK request it will copy the reply to the nlm_block.
* 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, struct file_lock *conf,
int result)
{
block->b_flags |= B_GOT_CALLBACK;
if (result == 0)
block->b_granted = 1;
else
block->b_flags |= B_TIMED_OUT;
if (conf) {
if (block->b_fl)
__locks_copy_lock(block->b_fl, conf);
}
}
static int nlmsvc_grant_deferred(struct file_lock *fl, struct file_lock *conf,
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, conf, 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");
}
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;
}
/*
* Since NLM uses two "keys" for tracking locks, we need to hash them down
* to one for the blocked_hash. Here, we're just xor'ing the host address
* with the pid in order to create a key value for picking a hash bucket.
*/
static unsigned long
nlmsvc_owner_key(struct file_lock *fl)
{
return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
}
const struct lock_manager_operations nlmsvc_lock_operations = {
.lm_compare_owner = nlmsvc_same_owner,
.lm_owner_key = nlmsvc_owner_key,
.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 (block) {
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;
}