linux/fs/dlm/ast.c
David Teigland 7fe2b3190b dlm: fix ordering of bast and cast
When both blocking and completion callbacks are queued for lock,
the dlm would always deliver the completion callback (cast) first.
In some cases the blocking callback (bast) is queued before the
cast, though, and should be delivered first.  This patch keeps
track of the order in which they were queued and delivers them
in that order.

This patch also keeps track of the granted mode in the last cast
and eliminates the following bast if the bast mode is compatible
with the preceding cast mode.  This happens when a remotely mastered
lock is demoted, e.g. EX->NL, in which case the local node queues
a cast immediately after sending the demote message.  In this way
a cast can be queued for a mode, e.g. NL, that makes an in-transit
bast extraneous.

Signed-off-by: David Teigland <teigland@redhat.com>
2010-02-24 11:46:53 -06:00

207 lines
4.7 KiB
C

/******************************************************************************
*******************************************************************************
**
** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
** Copyright (C) 2004-2010 Red Hat, Inc. All rights reserved.
**
** This copyrighted material is made available to anyone wishing to use,
** modify, copy, or redistribute it subject to the terms and conditions
** of the GNU General Public License v.2.
**
*******************************************************************************
******************************************************************************/
#include "dlm_internal.h"
#include "lock.h"
#include "user.h"
#include "ast.h"
#define WAKE_ASTS 0
static struct list_head ast_queue;
static spinlock_t ast_queue_lock;
static struct task_struct * astd_task;
static unsigned long astd_wakeflags;
static struct mutex astd_running;
void dlm_del_ast(struct dlm_lkb *lkb)
{
spin_lock(&ast_queue_lock);
if (lkb->lkb_ast_type & (AST_COMP | AST_BAST))
list_del(&lkb->lkb_astqueue);
spin_unlock(&ast_queue_lock);
}
void dlm_add_ast(struct dlm_lkb *lkb, int type, int mode)
{
if (lkb->lkb_flags & DLM_IFL_USER) {
dlm_user_add_ast(lkb, type, mode);
return;
}
spin_lock(&ast_queue_lock);
if (!(lkb->lkb_ast_type & (AST_COMP | AST_BAST))) {
kref_get(&lkb->lkb_ref);
list_add_tail(&lkb->lkb_astqueue, &ast_queue);
lkb->lkb_ast_first = type;
}
/* sanity check, this should not happen */
if ((type == AST_COMP) && (lkb->lkb_ast_type & AST_COMP))
log_print("repeat cast %d castmode %d lock %x %s",
mode, lkb->lkb_castmode,
lkb->lkb_id, lkb->lkb_resource->res_name);
lkb->lkb_ast_type |= type;
if (type == AST_BAST)
lkb->lkb_bastmode = mode;
else
lkb->lkb_castmode = mode;
spin_unlock(&ast_queue_lock);
set_bit(WAKE_ASTS, &astd_wakeflags);
wake_up_process(astd_task);
}
static void process_asts(void)
{
struct dlm_ls *ls = NULL;
struct dlm_rsb *r = NULL;
struct dlm_lkb *lkb;
void (*castfn) (void *astparam);
void (*bastfn) (void *astparam, int mode);
int type, first, bastmode, castmode, do_bast, do_cast, last_castmode;
repeat:
spin_lock(&ast_queue_lock);
list_for_each_entry(lkb, &ast_queue, lkb_astqueue) {
r = lkb->lkb_resource;
ls = r->res_ls;
if (dlm_locking_stopped(ls))
continue;
list_del(&lkb->lkb_astqueue);
type = lkb->lkb_ast_type;
lkb->lkb_ast_type = 0;
first = lkb->lkb_ast_first;
lkb->lkb_ast_first = 0;
bastmode = lkb->lkb_bastmode;
castmode = lkb->lkb_castmode;
castfn = lkb->lkb_astfn;
bastfn = lkb->lkb_bastfn;
spin_unlock(&ast_queue_lock);
do_cast = (type & AST_COMP) && castfn;
do_bast = (type & AST_BAST) && bastfn;
/* Skip a bast if its blocking mode is compatible with the
granted mode of the preceding cast. */
if (do_bast) {
if (first == AST_COMP)
last_castmode = castmode;
else
last_castmode = lkb->lkb_castmode_done;
if (dlm_modes_compat(bastmode, last_castmode))
do_bast = 0;
}
if (first == AST_COMP) {
if (do_cast)
castfn(lkb->lkb_astparam);
if (do_bast)
bastfn(lkb->lkb_astparam, bastmode);
} else if (first == AST_BAST) {
if (do_bast)
bastfn(lkb->lkb_astparam, bastmode);
if (do_cast)
castfn(lkb->lkb_astparam);
} else {
log_error(ls, "bad ast_first %d ast_type %d",
first, type);
}
if (do_cast)
lkb->lkb_castmode_done = castmode;
if (do_bast)
lkb->lkb_bastmode_done = bastmode;
/* this removes the reference added by dlm_add_ast
and may result in the lkb being freed */
dlm_put_lkb(lkb);
cond_resched();
goto repeat;
}
spin_unlock(&ast_queue_lock);
}
static inline int no_asts(void)
{
int ret;
spin_lock(&ast_queue_lock);
ret = list_empty(&ast_queue);
spin_unlock(&ast_queue_lock);
return ret;
}
static int dlm_astd(void *data)
{
while (!kthread_should_stop()) {
set_current_state(TASK_INTERRUPTIBLE);
if (!test_bit(WAKE_ASTS, &astd_wakeflags))
schedule();
set_current_state(TASK_RUNNING);
mutex_lock(&astd_running);
if (test_and_clear_bit(WAKE_ASTS, &astd_wakeflags))
process_asts();
mutex_unlock(&astd_running);
}
return 0;
}
void dlm_astd_wake(void)
{
if (!no_asts()) {
set_bit(WAKE_ASTS, &astd_wakeflags);
wake_up_process(astd_task);
}
}
int dlm_astd_start(void)
{
struct task_struct *p;
int error = 0;
INIT_LIST_HEAD(&ast_queue);
spin_lock_init(&ast_queue_lock);
mutex_init(&astd_running);
p = kthread_run(dlm_astd, NULL, "dlm_astd");
if (IS_ERR(p))
error = PTR_ERR(p);
else
astd_task = p;
return error;
}
void dlm_astd_stop(void)
{
kthread_stop(astd_task);
}
void dlm_astd_suspend(void)
{
mutex_lock(&astd_running);
}
void dlm_astd_resume(void)
{
mutex_unlock(&astd_running);
}