android_kernel_xiaomi_sm8350/fs/lockd/svclock.c

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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/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 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);
/*
* Insert a blocked lock into the global list
*/
static void
nlmsvc_insert_block(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;
}
/*
* Remove a block from the global list
*/
static inline void
nlmsvc_remove_block(struct nlm_block *block)
{
if (!list_empty(&block->b_list)) {
list_del_init(&block->b_list);
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 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 = NULL;
/* Create host handle for callback */
host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
if (host == NULL)
return 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:
nlm_release_call(call);
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;
dprintk("lockd: freeing block %p...\n", block);
/* Remove block from file's list of blocks */
mutex_lock(&file->f_mutex);
list_del_init(&block->b_flist);
mutex_unlock(&file->f_mutex);
nlmsvc_freegrantargs(block->b_call);
nlm_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(&block->b_count, nlmsvc_free_block);
}
/*
* 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);
}
/*
* 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_lock *lock, int wait, struct nlm_cookie *cookie)
{
struct nlm_block *block, *newblock = NULL;
int error;
__be32 ret;
dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
file->f_file->f_path.dentry->d_inode->i_sb->s_id,
file->f_file->f_path.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 */
mutex_lock(&file->f_mutex);
/* Get existing block (in case client is busy-waiting) */
block = nlmsvc_lookup_block(file, lock);
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, NULL);
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_mutex as nlmsvc_create_block may try to
* to claim it while doing host garbage collection */
if (newblock == NULL) {
mutex_unlock(&file->f_mutex);
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:
mutex_unlock(&file->f_mutex);
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.
*/
__be32
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_path.dentry->d_inode->i_sb->s_id,
file->f_file->f_path.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)) {
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;
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.
*/
__be32
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_path.dentry->d_inode->i_sb->s_id,
file->f_file->f_path.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, 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 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_path.dentry->d_inode->i_sb->s_id,
file->f_file->f_path.dentry->d_inode->i_ino,
lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
mutex_lock(&file->f_mutex);
block = nlmsvc_lookup_block(file, lock);
mutex_unlock(&file->f_mutex);
if (block != NULL) {
status = nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
}
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 *block;
dprintk("lockd: VFS unblock notification for block %p\n", fl);
list_for_each_entry(block, &nlm_blocked, b_list) {
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);
/* 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, NULL);
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);
return;
default:
printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
-error, __FUNCTION__);
nlmsvc_insert_block(block, 10 * HZ);
return;
}
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);
nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, &nlmsvc_grant_ops);
}
/*
* 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");
/* 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(block, timeout);
svc_wake_up(block->b_daemon);
}
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);
}
/*
* 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;
while (!list_empty(&nlm_blocked)) {
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;
}
dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
block, block->b_when);
kref_get(&block->b_count);
nlmsvc_grant_blocked(block);
nlmsvc_release_block(block);
}
return timeout;
}