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ocfs2 fix o2dlm dlm run purgelist (rev 3) 

This patch fixes two problems in dlm_run_purgelist

1. If a lockres is found to be in use, dlm_run_purgelist keeps trying to purge
the same lockres instead of trying the next lockres.

2. When a lockres is found unused, dlm_run_purgelist releases lockres spinlock
before setting DLM_LOCK_RES_DROPPING_REF and calls dlm_purge_lockres.
spinlock is reacquired but in this window lockres can get reused. This leads
to BUG.

This patch modifies dlm_run_purgelist to skip lockres if it's in use and purge
 next lockres. It also sets DLM_LOCK_RES_DROPPING_REF before releasing the
lockres spinlock protecting it from getting reused.

Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Acked-by: Sunil Mushran <sunil.mushran@oracle.com>
Cc: stable@kernel.org
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This commit is contained in:
Srinivas Eeda 2010-07-19 16:04:12 -07:00 committed by Joel Becker
parent 6d98c3ccb5
commit 7beaf24378
1 changed files with 34 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
fs/ocfs2/dlm/dlmthread.c
View File

@ -152,45 +152,25 @@ void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
spin_unlock(&dlm->spinlock);
}
static int dlm_purge_lockres(struct dlm_ctxt *dlm,
static void dlm_purge_lockres(struct dlm_ctxt *dlm,
struct dlm_lock_resource *res)
{
int master;
int ret = 0;
spin_lock(&res->spinlock);
if (!__dlm_lockres_unused(res)) {
mlog(0, "%s:%.*s: tried to purge but not unused\n",
dlm->name, res->lockname.len, res->lockname.name);
__dlm_print_one_lock_resource(res);
spin_unlock(&res->spinlock);
BUG();
}
if (res->state & DLM_LOCK_RES_MIGRATING) {
mlog(0, "%s:%.*s: Delay dropref as this lockres is "
"being remastered\n", dlm->name, res->lockname.len,
res->lockname.name);
/* Re-add the lockres to the end of the purge list */
if (!list_empty(&res->purge)) {
list_del_init(&res->purge);
list_add_tail(&res->purge, &dlm->purge_list);
}
spin_unlock(&res->spinlock);
return 0;
}
assert_spin_locked(&dlm->spinlock);
assert_spin_locked(&res->spinlock);
master = (res->owner == dlm->node_num);
if (!master)
res->state |= DLM_LOCK_RES_DROPPING_REF;
spin_unlock(&res->spinlock);
mlog(0, "purging lockres %.*s, master = %d\n", res->lockname.len,
res->lockname.name, master);
if (!master) {
res->state |= DLM_LOCK_RES_DROPPING_REF;
/* drop spinlock... retake below */
spin_unlock(&res->spinlock);
spin_unlock(&dlm->spinlock);
spin_lock(&res->spinlock);
@ -208,31 +188,35 @@ static int dlm_purge_lockres(struct dlm_ctxt *dlm,
mlog(0, "%s:%.*s: dlm_deref_lockres returned %d\n",
dlm->name, res->lockname.len, res->lockname.name, ret);
spin_lock(&dlm->spinlock);
spin_lock(&res->spinlock);
}
spin_lock(&res->spinlock);
if (!list_empty(&res->purge)) {
mlog(0, "removing lockres %.*s:%p from purgelist, "
"master = %d\n", res->lockname.len, res->lockname.name,
res, master);
list_del_init(&res->purge);
spin_unlock(&res->spinlock);
dlm_lockres_put(res);
dlm->purge_count--;
} else
spin_unlock(&res->spinlock);
}
if (!__dlm_lockres_unused(res)) {
mlog(ML_ERROR, "found lockres %s:%.*s: in use after deref\n",
dlm->name, res->lockname.len, res->lockname.name);
__dlm_print_one_lock_resource(res);
BUG();
}
__dlm_unhash_lockres(res);
/* lockres is not in the hash now. drop the flag and wake up
* any processes waiting in dlm_get_lock_resource. */
if (!master) {
spin_lock(&res->spinlock);
res->state &= ~DLM_LOCK_RES_DROPPING_REF;
spin_unlock(&res->spinlock);
wake_up(&res->wq);
}
return 0;
} else
spin_unlock(&res->spinlock);
}
static void dlm_run_purge_list(struct dlm_ctxt *dlm,
@ -251,17 +235,7 @@ static void dlm_run_purge_list(struct dlm_ctxt *dlm,
lockres = list_entry(dlm->purge_list.next,
struct dlm_lock_resource, purge);
/* Status of the lockres *might* change so double
* check. If the lockres is unused, holding the dlm
* spinlock will prevent people from getting and more
* refs on it -- there's no need to keep the lockres
* spinlock. */
spin_lock(&lockres->spinlock);
unused = __dlm_lockres_unused(lockres);
spin_unlock(&lockres->spinlock);
if (!unused)
continue;
purge_jiffies = lockres->last_used +
msecs_to_jiffies(DLM_PURGE_INTERVAL_MS);
@ -273,15 +247,29 @@ static void dlm_run_purge_list(struct dlm_ctxt *dlm,
* in tail order, we can stop at the first
* unpurgable resource -- anyone added after
* him will have a greater last_used value */
spin_unlock(&lockres->spinlock);
break;
}
/* Status of the lockres *might* change so double
* check. If the lockres is unused, holding the dlm
* spinlock will prevent people from getting and more
* refs on it. */
unused = __dlm_lockres_unused(lockres);
if (!unused ||
(lockres->state & DLM_LOCK_RES_MIGRATING)) {
mlog(0, "lockres %s:%.*s: is in use or "
"being remastered, used %d, state %d\n",
dlm->name, lockres->lockname.len,
lockres->lockname.name, !unused, lockres->state);
list_move_tail(&dlm->purge_list, &lockres->purge);
spin_unlock(&lockres->spinlock);
continue;
}
dlm_lockres_get(lockres);
/* This may drop and reacquire the dlm spinlock if it
* has to do migration. */
if (dlm_purge_lockres(dlm, lockres))
BUG();
dlm_purge_lockres(dlm, lockres);
dlm_lockres_put(lockres);