From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sunil Mushran Date: Tue, 22 Jun 2010 16:22:00 -0700 Subject: [Ocfs2-devel] [PATCH 1/1] ocfs2 fix o2dlm dlm run purgelist(bug 9094491) - rev3 In-Reply-To: <1277228012-13836-1-git-send-email-srinivas.eeda@oracle.com> References: <1277228012-13836-1-git-send-email-srinivas.eeda@oracle.com> Message-ID: <4C214598.2060104@oracle.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Comments inlined. Getting there. Some more cleanups. On 06/22/2010 10:33 AM, Srinivas Eeda wrote: > There are 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 > --- > fs/ocfs2/dlm/dlmthread.c | 76 ++++++++++++++++++++-------------------------- > 1 files changed, 33 insertions(+), 43 deletions(-) > > diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c > index 11a6d1f..cb74689 100644 > --- a/fs/ocfs2/dlm/dlmthread.c > +++ b/fs/ocfs2/dlm/dlmthread.c > @@ -152,45 +152,26 @@ 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) { > /* drop spinlock... retake below */ > + spin_unlock(&res->spinlock); > spin_unlock(&dlm->spinlock); > > spin_lock(&res->spinlock); > This can do with more cleanup. + 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 +189,35 @@ 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); > + } > > - __dlm_unhash_lockres(res); > + if (__dlm_lockres_unused(res)) > + __dlm_unhash_lockres(res); > + else { > + 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(); > + } > Blocks that BUG should be separated if possible. Improves readability. + 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 +236,7 @@ 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 +248,30 @@ 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\n", dlm->name, > + lockres->lockname.len, lockres->lockname.name); > + 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); > > This comment is dated. We don't migrate in purge_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);