/*
* 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_release_block(struct nlm_block *block);
static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
static int 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 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);
kref_get(&block->b_count);
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;
nlmsvc_release_block(block);
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;
}
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 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;
}
if (block != NULL)
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.
*/
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);
kref_init(&block->b_count);
if (!nlmsvc_setgrantargs(&block->b_call, lock))
goto failed_free;
/* Set notifier function for VFS, and init args */
block->b_call.a_args.lock.fl.fl_flags |= FL_SLEEP;
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_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_file->f_file, &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;
struct nlm_block **bp;
dprintk("lockd: freeing block %p...\n", block);
/* 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);
nlmsvc_freegrantargs(&block->b_call);
kfree(block);
}
static void nlmsvc_release_block(struct nlm_block *block)
{
if (block != NULL)
kref_put(&block->b_count, nlmsvc_free_block);
}
/*
* 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_unlink_block(block);
}
}
up(&file->f_sema);
return 0;
}
/*
* 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 = system_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) {
nlmsvc_freegrantargs(call);
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)
{
struct file_lock *fl = &call->a_args.lock.fl;
/*
* Check whether we allocated memory for the owner.
*/
if (call->a_args.lock.oh.data != (u8 *) call->a_owner) {
kfree(call->a_args.lock.oh.data);
}
if (fl->fl_ops && fl->fl_ops->fl_release_private)
fl->fl_ops->fl_release_private(fl);
if (fl->fl_lmops && fl->fl_lmops->fl_release_private)
fl->fl_lmops->fl_release_private(fl);
}
/*
* 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 nlm_block *block, *newblock = NULL;
int error;
u32 ret;
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);
lock->fl.fl_flags &= ~FL_SLEEP;
again:
/* Lock file against concurrent access */
down(&file->f_sema);
/* Get existing block (in case client is busy-waiting) */
block = nlmsvc_lookup_block(file, lock, 0);
if (block == NULL) {
if (newblock != NULL)
lock = &newblock->b_call.a_args.lock;
} else
lock = &block->b_call.a_args.lock;
error = posix_lock_file(file->f_file, &lock->fl);
lock->fl.fl_flags &= ~FL_SLEEP;
dprintk("lockd: posix_lock_file returned %d\n", error);
switch(error) {
case 0:
ret = nlm_granted;
goto out;
case -EAGAIN:
break;
case -EDEADLK:
ret = nlm_deadlock;
goto out;
default: /* includes ENOLCK */
ret = nlm_lck_denied_nolocks;
goto out;
}
ret = nlm_lck_denied;
if (!wait)
goto out;
ret = nlm_lck_blocked;
if (block != NULL)
goto out;
/* 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 (newblock == NULL) {
up(&file->f_sema);
dprintk("lockd: blocking on this lock (allocating).\n");
if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
return nlm_lck_denied_nolocks;
goto again;
}
/* Append to list of blocked */
nlmsvc_insert_block(newblock, NLM_NEVER);
out:
up(&file->f_sema);
nlmsvc_release_block(newblock);
nlmsvc_release_block(block);
dprintk("lockd: nlmsvc_lock returned %u\n", ret);
return ret;
}
/*
* Test for presence of a conflicting lock.
*/
u32
nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
struct nlm_lock *conflock)
{
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 (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
conflock->fl.fl_type,
(long long)conflock->fl.fl_start,
(long long)conflock->fl.fl_end);
conflock->caller = "somehost"; /* FIXME */
conflock->oh.len = 0; /* don't return OH info */
conflock->svid = conflock->fl.fl_pid;
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_unlink_block(block);
nlmsvc_release_block(block);
}
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;
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_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 */
lock->fl.fl_flags |= FL_SLEEP;
error = posix_lock_file(file->f_file, &lock->fl);
lock->fl.fl_flags &= ~FL_SLEEP;
switch (error) {
case 0:
break;
case -EAGAIN:
dprintk("lockd: lock still blocked\n");
nlmsvc_insert_block(block, NLM_NEVER);
goto out_unlock;
default:
printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
-error, __FUNCTION__);
nlmsvc_insert_block(block, 10 * HZ);
goto out_unlock;
}
callback:
/* Lock was granted by VFS. */
dprintk("lockd: GRANTing blocked lock.\n");
block->b_granted = 1;
/* Schedule next grant callback in 30 seconds */
nlmsvc_insert_block(block, 30 * HZ);
/* Call the client */
kref_get(&block->b_count);
if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
&nlmsvc_grant_ops) < 0)
nlmsvc_release_block(block);
out_unlock:
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 = container_of(call, struct nlm_block, b_call);
unsigned long timeout;
dprintk("lockd: GRANT_MSG RPC callback\n");
/* 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);
}
void nlmsvc_grant_release(void *data)
{
nlmsvc_release_block(data);
}
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 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);
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);
}
}
up(&file->f_sema);
nlm_release_file(file);
nlmsvc_release_block(block);
}
/*
* 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);
kref_get(&block->b_count);
if (block->b_done)
nlmsvc_unlink_block(block);
else
nlmsvc_grant_blocked(block);
nlmsvc_release_block(block);
}
if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
return (block->b_when - jiffies);
return MAX_SCHEDULE_TIMEOUT;
}
