[DLM] cancel in conversion deadlock [4/6]
When conversion deadlock is detected, cancel the conversion and return EDEADLK to the application. This is a new default behavior where before the dlm would allow the deadlock to exist indefinately. The DLM_LKF_NODLCKWT flag can now be used in a conversion to prevent the dlm from performing conversion deadlock detection/cancelation on it. The DLM_LKF_CONVDEADLK flag can continue to be used as before to tell the dlm to demote the granted mode of the lock being converted if it gets into a conversion deadlock. Signed-off-by: David Teigland <teigland@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
David Teigland
Steven Whitehouse
parent
d7db923ea4
commit
c85d65e914
195
fs/dlm/lock.c
195
fs/dlm/lock.c
|
|
@ -1408,10 +1408,8 @@ static int queue_conflict(struct list_head *head, struct dlm_lkb *lkb)
|
|||
* queue for one resource. The granted mode of each lock blocks the requested
|
||||
* mode of the other lock."
|
||||
*
|
||||
* Part 2: if the granted mode of lkb is preventing the first lkb in the
|
||||
* convert queue from being granted, then demote lkb (set grmode to NL).
|
||||
* This second form requires that we check for conv-deadlk even when
|
||||
* now == 0 in _can_be_granted().
|
||||
* Part 2: if the granted mode of lkb is preventing an earlier lkb in the
|
||||
* convert queue from being granted, then deadlk/demote lkb.
|
||||
*
|
||||
* Example:
|
||||
* Granted Queue: empty
|
||||
|
|
@ -1420,41 +1418,52 @@ static int queue_conflict(struct list_head *head, struct dlm_lkb *lkb)
|
|||
*
|
||||
* The first lock can't be granted because of the granted mode of the second
|
||||
* lock and the second lock can't be granted because it's not first in the
|
||||
* list. We demote the granted mode of the second lock (the lkb passed to this
|
||||
* function).
|
||||
* list. We either cancel lkb's conversion (PR->EX) and return EDEADLK, or we
|
||||
* demote the granted mode of lkb (from PR to NL) if it has the CONVDEADLK
|
||||
* flag set and return DEMOTED in the lksb flags.
|
||||
*
|
||||
* After the resolution, the "grant pending" function needs to go back and try
|
||||
* to grant locks on the convert queue again since the first lock can now be
|
||||
* granted.
|
||||
* Originally, this function detected conv-deadlk in a more limited scope:
|
||||
* - if !modes_compat(lkb1, lkb2) && !modes_compat(lkb2, lkb1), or
|
||||
* - if lkb1 was the first entry in the queue (not just earlier), and was
|
||||
* blocked by the granted mode of lkb2, and there was nothing on the
|
||||
* granted queue preventing lkb1 from being granted immediately, i.e.
|
||||
* lkb2 was the only thing preventing lkb1 from being granted.
|
||||
*
|
||||
* That second condition meant we'd only say there was conv-deadlk if
|
||||
* resolving it (by demotion) would lead to the first lock on the convert
|
||||
* queue being granted right away. It allowed conversion deadlocks to exist
|
||||
* between locks on the convert queue while they couldn't be granted anyway.
|
||||
*
|
||||
* Now, we detect and take action on conversion deadlocks immediately when
|
||||
* they're created, even if they may not be immediately consequential. If
|
||||
* lkb1 exists anywhere in the convert queue and lkb2 comes in with a granted
|
||||
* mode that would prevent lkb1's conversion from being granted, we do a
|
||||
* deadlk/demote on lkb2 right away and don't let it onto the convert queue.
|
||||
* I think this means that the lkb_is_ahead condition below should always
|
||||
* be zero, i.e. there will never be conv-deadlk between two locks that are
|
||||
* both already on the convert queue.
|
||||
*/
|
||||
|
||||
static int conversion_deadlock_detect(struct dlm_rsb *rsb, struct dlm_lkb *lkb)
|
||||
static int conversion_deadlock_detect(struct dlm_rsb *r, struct dlm_lkb *lkb2)
|
||||
{
|
||||
struct dlm_lkb *this, *first = NULL, *self = NULL;
|
||||
struct dlm_lkb *lkb1;
|
||||
int lkb_is_ahead = 0;
|
||||
|
||||
list_for_each_entry(this, &rsb->res_convertqueue, lkb_statequeue) {
|
||||
if (!first)
|
||||
first = this;
|
||||
if (this == lkb) {
|
||||
self = lkb;
|
||||
list_for_each_entry(lkb1, &r->res_convertqueue, lkb_statequeue) {
|
||||
if (lkb1 == lkb2) {
|
||||
lkb_is_ahead = 1;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (!modes_compat(this, lkb) && !modes_compat(lkb, this))
|
||||
return 1;
|
||||
if (!lkb_is_ahead) {
|
||||
if (!modes_compat(lkb2, lkb1))
|
||||
return 1;
|
||||
} else {
|
||||
if (!modes_compat(lkb2, lkb1) &&
|
||||
!modes_compat(lkb1, lkb2))
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
/* if lkb is on the convert queue and is preventing the first
|
||||
from being granted, then there's deadlock and we demote lkb.
|
||||
multiple converting locks may need to do this before the first
|
||||
converting lock can be granted. */
|
||||
|
||||
if (self && self != first) {
|
||||
if (!modes_compat(lkb, first) &&
|
||||
!queue_conflict(&rsb->res_grantqueue, first))
|
||||
return 1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -1583,42 +1592,57 @@ static int _can_be_granted(struct dlm_rsb *r, struct dlm_lkb *lkb, int now)
|
|||
if (!now && !conv && list_empty(&r->res_convertqueue) &&
|
||||
first_in_list(lkb, &r->res_waitqueue))
|
||||
return 1;
|
||||
|
||||
out:
|
||||
/*
|
||||
* The following, enabled by CONVDEADLK, departs from VMS.
|
||||
*/
|
||||
|
||||
if (conv && (lkb->lkb_exflags & DLM_LKF_CONVDEADLK) &&
|
||||
conversion_deadlock_detect(r, lkb)) {
|
||||
lkb->lkb_grmode = DLM_LOCK_NL;
|
||||
lkb->lkb_sbflags |= DLM_SBF_DEMOTED;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* The ALTPR and ALTCW flags aren't traditional lock manager flags, but are a
|
||||
* simple way to provide a big optimization to applications that can use them.
|
||||
*/
|
||||
|
||||
static int can_be_granted(struct dlm_rsb *r, struct dlm_lkb *lkb, int now)
|
||||
static int can_be_granted(struct dlm_rsb *r, struct dlm_lkb *lkb, int now,
|
||||
int *err)
|
||||
{
|
||||
uint32_t flags = lkb->lkb_exflags;
|
||||
int rv;
|
||||
int8_t alt = 0, rqmode = lkb->lkb_rqmode;
|
||||
int8_t is_convert = (lkb->lkb_grmode != DLM_LOCK_IV);
|
||||
|
||||
if (err)
|
||||
*err = 0;
|
||||
|
||||
rv = _can_be_granted(r, lkb, now);
|
||||
if (rv)
|
||||
goto out;
|
||||
|
||||
if (lkb->lkb_sbflags & DLM_SBF_DEMOTED)
|
||||
goto out;
|
||||
/*
|
||||
* The CONVDEADLK flag is non-standard and tells the dlm to resolve
|
||||
* conversion deadlocks by demoting grmode to NL, otherwise the dlm
|
||||
* cancels one of the locks.
|
||||
*/
|
||||
|
||||
if (rqmode != DLM_LOCK_PR && flags & DLM_LKF_ALTPR)
|
||||
if (is_convert && can_be_queued(lkb) &&
|
||||
conversion_deadlock_detect(r, lkb)) {
|
||||
if (lkb->lkb_exflags & DLM_LKF_CONVDEADLK) {
|
||||
lkb->lkb_grmode = DLM_LOCK_NL;
|
||||
lkb->lkb_sbflags |= DLM_SBF_DEMOTED;
|
||||
} else if (!(lkb->lkb_exflags & DLM_LKF_NODLCKWT)) {
|
||||
if (err)
|
||||
*err = -EDEADLK;
|
||||
else {
|
||||
log_print("can_be_granted deadlock %x now %d",
|
||||
lkb->lkb_id, now);
|
||||
dlm_dump_rsb(r);
|
||||
}
|
||||
}
|
||||
goto out;
|
||||
}
|
||||
|
||||
/*
|
||||
* The ALTPR and ALTCW flags are non-standard and tell the dlm to try
|
||||
* to grant a request in a mode other than the normal rqmode. It's a
|
||||
* simple way to provide a big optimization to applications that can
|
||||
* use them.
|
||||
*/
|
||||
|
||||
if (rqmode != DLM_LOCK_PR && (lkb->lkb_exflags & DLM_LKF_ALTPR))
|
||||
alt = DLM_LOCK_PR;
|
||||
else if (rqmode != DLM_LOCK_CW && flags & DLM_LKF_ALTCW)
|
||||
else if (rqmode != DLM_LOCK_CW && (lkb->lkb_exflags & DLM_LKF_ALTCW))
|
||||
alt = DLM_LOCK_CW;
|
||||
|
||||
if (alt) {
|
||||
|
|
@ -1633,10 +1657,20 @@ static int can_be_granted(struct dlm_rsb *r, struct dlm_lkb *lkb, int now)
|
|||
return rv;
|
||||
}
|
||||
|
||||
/* FIXME: I don't think that can_be_granted() can/will demote or find deadlock
|
||||
for locks pending on the convert list. Once verified (watch for these
|
||||
log_prints), we should be able to just call _can_be_granted() and not
|
||||
bother with the demote/deadlk cases here (and there's no easy way to deal
|
||||
with a deadlk here, we'd have to generate something like grant_lock with
|
||||
the deadlk error.) */
|
||||
|
||||
/* returns the highest requested mode of all blocked conversions */
|
||||
|
||||
static int grant_pending_convert(struct dlm_rsb *r, int high)
|
||||
{
|
||||
struct dlm_lkb *lkb, *s;
|
||||
int hi, demoted, quit, grant_restart, demote_restart;
|
||||
int deadlk;
|
||||
|
||||
quit = 0;
|
||||
restart:
|
||||
|
|
@ -1646,14 +1680,29 @@ static int grant_pending_convert(struct dlm_rsb *r, int high)
|
|||
|
||||
list_for_each_entry_safe(lkb, s, &r->res_convertqueue, lkb_statequeue) {
|
||||
demoted = is_demoted(lkb);
|
||||
if (can_be_granted(r, lkb, 0)) {
|
||||
deadlk = 0;
|
||||
|
||||
if (can_be_granted(r, lkb, 0, &deadlk)) {
|
||||
grant_lock_pending(r, lkb);
|
||||
grant_restart = 1;
|
||||
} else {
|
||||
hi = max_t(int, lkb->lkb_rqmode, hi);
|
||||
if (!demoted && is_demoted(lkb))
|
||||
demote_restart = 1;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (!demoted && is_demoted(lkb)) {
|
||||
log_print("WARN: pending demoted %x node %d %s",
|
||||
lkb->lkb_id, lkb->lkb_nodeid, r->res_name);
|
||||
demote_restart = 1;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (deadlk) {
|
||||
log_print("WARN: pending deadlock %x node %d %s",
|
||||
lkb->lkb_id, lkb->lkb_nodeid, r->res_name);
|
||||
dlm_dump_rsb(r);
|
||||
continue;
|
||||
}
|
||||
|
||||
hi = max_t(int, lkb->lkb_rqmode, hi);
|
||||
}
|
||||
|
||||
if (grant_restart)
|
||||
|
|
@ -1671,7 +1720,7 @@ static int grant_pending_wait(struct dlm_rsb *r, int high)
|
|||
struct dlm_lkb *lkb, *s;
|
||||
|
||||
list_for_each_entry_safe(lkb, s, &r->res_waitqueue, lkb_statequeue) {
|
||||
if (can_be_granted(r, lkb, 0))
|
||||
if (can_be_granted(r, lkb, 0, NULL))
|
||||
grant_lock_pending(r, lkb);
|
||||
else
|
||||
high = max_t(int, lkb->lkb_rqmode, high);
|
||||
|
|
@ -2121,7 +2170,7 @@ static int do_request(struct dlm_rsb *r, struct dlm_lkb *lkb)
|
|||
{
|
||||
int error = 0;
|
||||
|
||||
if (can_be_granted(r, lkb, 1)) {
|
||||
if (can_be_granted(r, lkb, 1, NULL)) {
|
||||
grant_lock(r, lkb);
|
||||
queue_cast(r, lkb, 0);
|
||||
goto out;
|
||||
|
|
@ -2147,16 +2196,32 @@ static int do_request(struct dlm_rsb *r, struct dlm_lkb *lkb)
|
|||
static int do_convert(struct dlm_rsb *r, struct dlm_lkb *lkb)
|
||||
{
|
||||
int error = 0;
|
||||
int deadlk = 0;
|
||||
|
||||
/* changing an existing lock may allow others to be granted */
|
||||
|
||||
if (can_be_granted(r, lkb, 1)) {
|
||||
if (can_be_granted(r, lkb, 1, &deadlk)) {
|
||||
grant_lock(r, lkb);
|
||||
queue_cast(r, lkb, 0);
|
||||
grant_pending_locks(r);
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* can_be_granted() detected that this lock would block in a conversion
|
||||
deadlock, so we leave it on the granted queue and return EDEADLK in
|
||||
the ast for the convert. */
|
||||
|
||||
if (deadlk) {
|
||||
/* it's left on the granted queue */
|
||||
log_debug(r->res_ls, "deadlock %x node %d sts%d g%d r%d %s",
|
||||
lkb->lkb_id, lkb->lkb_nodeid, lkb->lkb_status,
|
||||
lkb->lkb_grmode, lkb->lkb_rqmode, r->res_name);
|
||||
revert_lock(r, lkb);
|
||||
queue_cast(r, lkb, -EDEADLK);
|
||||
error = -EDEADLK;
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* is_demoted() means the can_be_granted() above set the grmode
|
||||
to NL, and left us on the granted queue. This auto-demotion
|
||||
(due to CONVDEADLK) might mean other locks, and/or this lock, are
|
||||
|
|
@ -2438,7 +2503,7 @@ int dlm_lock(dlm_lockspace_t *lockspace,
|
|||
out_put:
|
||||
if (convert || error)
|
||||
__put_lkb(ls, lkb);
|
||||
if (error == -EAGAIN)
|
||||
if (error == -EAGAIN || error == -EDEADLK)
|
||||
error = 0;
|
||||
out:
|
||||
dlm_unlock_recovery(ls);
|
||||
|
|
@ -3312,6 +3377,12 @@ static void __receive_convert_reply(struct dlm_rsb *r, struct dlm_lkb *lkb,
|
|||
queue_cast(r, lkb, -EAGAIN);
|
||||
break;
|
||||
|
||||
case -EDEADLK:
|
||||
receive_flags_reply(lkb, ms);
|
||||
revert_lock_pc(r, lkb);
|
||||
queue_cast(r, lkb, -EDEADLK);
|
||||
break;
|
||||
|
||||
case -EINPROGRESS:
|
||||
/* convert was queued on remote master */
|
||||
receive_flags_reply(lkb, ms);
|
||||
|
|
@ -4284,7 +4355,7 @@ int dlm_user_convert(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
|
|||
|
||||
error = convert_lock(ls, lkb, &args);
|
||||
|
||||
if (error == -EINPROGRESS || error == -EAGAIN)
|
||||
if (error == -EINPROGRESS || error == -EAGAIN || error == -EDEADLK)
|
||||
error = 0;
|
||||
out_put:
|
||||
dlm_put_lkb(lkb);
|
||||
|
|
|
|||
|
|
@ -85,7 +85,11 @@
|
|||
* Only relevant to locks originating in userspace. A persistent lock will not
|
||||
* be removed if the process holding the lock exits.
|
||||
*
|
||||
* DLM_LKF_NODLKWT
|
||||
* DLM_LKF_NODLCKWT
|
||||
*
|
||||
* Do not cancel the lock if it gets into conversion deadlock.
|
||||
* Exclude this lock from being monitored due to DLM_LSFL_TIMEWARN.
|
||||
*
|
||||
* DLM_LKF_NODLCKBLK
|
||||
*
|
||||
* net yet implemented
|
||||
|
|
|
|||
Loading…
Reference in New Issue