From b0d4f817ba5de8adb875ace594554a96d7737710 Mon Sep 17 00:00:00 2001 From: Sunil Mushran Date: Tue, 16 Dec 2008 15:49:22 -0800 Subject: ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list This patch adds a new lock, dlm->tracking_lock, to protect adding/removing lockres' to/from the dlm->tracking_list. We were previously using dlm->spinlock for the same, but that proved inadequate as we could be freeing a lockres from a context that did not hold that lock. As the new lock only protects this list, we can explicitly take it when removing the lockres from the tracking list. This bug was exposed when testing multiple processes concurrently flock() the same file. Signed-off-by: Sunil Mushran Signed-off-by: Mark Fasheh --- fs/ocfs2/dlm/dlmcommon.h | 3 +++ fs/ocfs2/dlm/dlmdebug.c | 53 ++++++++++++++++++++++-------------------------- fs/ocfs2/dlm/dlmdomain.c | 1 + fs/ocfs2/dlm/dlmmaster.c | 10 +++++++++ 4 files changed, 38 insertions(+), 29 deletions(-) diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h index d5a86fb81a4..bb53714813a 100644 --- a/fs/ocfs2/dlm/dlmcommon.h +++ b/fs/ocfs2/dlm/dlmcommon.h @@ -140,6 +140,7 @@ struct dlm_ctxt unsigned int purge_count; spinlock_t spinlock; spinlock_t ast_lock; + spinlock_t track_lock; char *name; u8 node_num; u32 key; @@ -316,6 +317,8 @@ struct dlm_lock_resource * put on a list for the dlm thread to run. */ unsigned long last_used; + struct dlm_ctxt *dlm; + unsigned migration_pending:1; atomic_t asts_reserved; spinlock_t spinlock; diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c index 1b81dcba175..b32f60a5acf 100644 --- a/fs/ocfs2/dlm/dlmdebug.c +++ b/fs/ocfs2/dlm/dlmdebug.c @@ -630,43 +630,38 @@ static void *lockres_seq_start(struct seq_file *m, loff_t *pos) { struct debug_lockres *dl = m->private; struct dlm_ctxt *dlm = dl->dl_ctxt; + struct dlm_lock_resource *oldres = dl->dl_res; struct dlm_lock_resource *res = NULL; + struct list_head *track_list; - spin_lock(&dlm->spinlock); + spin_lock(&dlm->track_lock); + if (oldres) + track_list = &oldres->tracking; + else + track_list = &dlm->tracking_list; - if (dl->dl_res) { - list_for_each_entry(res, &dl->dl_res->tracking, tracking) { - if (dl->dl_res) { - dlm_lockres_put(dl->dl_res); - dl->dl_res = NULL; - } - if (&res->tracking == &dlm->tracking_list) { - mlog(0, "End of list found, %p\n", res); - dl = NULL; - break; - } + list_for_each_entry(res, track_list, tracking) { + if (&res->tracking == &dlm->tracking_list) + res = NULL; + else dlm_lockres_get(res); - dl->dl_res = res; - break; - } - } else { - if (!list_empty(&dlm->tracking_list)) { - list_for_each_entry(res, &dlm->tracking_list, tracking) - break; - dlm_lockres_get(res); - dl->dl_res = res; - } else - dl = NULL; + break; } + spin_unlock(&dlm->track_lock); - if (dl) { - spin_lock(&dl->dl_res->spinlock); - dump_lockres(dl->dl_res, dl->dl_buf, dl->dl_len - 1); - spin_unlock(&dl->dl_res->spinlock); - } + if (oldres) + dlm_lockres_put(oldres); - spin_unlock(&dlm->spinlock); + dl->dl_res = res; + + if (res) { + spin_lock(&res->spinlock); + dump_lockres(res, dl->dl_buf, dl->dl_len - 1); + spin_unlock(&res->spinlock); + } else + dl = NULL; + /* passed to seq_show */ return dl; } diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c index 63f8125824e..d8d578f4561 100644 --- a/fs/ocfs2/dlm/dlmdomain.c +++ b/fs/ocfs2/dlm/dlmdomain.c @@ -1550,6 +1550,7 @@ static struct dlm_ctxt *dlm_alloc_ctxt(const char *domain, spin_lock_init(&dlm->spinlock); spin_lock_init(&dlm->master_lock); spin_lock_init(&dlm->ast_lock); + spin_lock_init(&dlm->track_lock); INIT_LIST_HEAD(&dlm->list); INIT_LIST_HEAD(&dlm->dirty_list); INIT_LIST_HEAD(&dlm->reco.resources); diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c index 92fd1d7d612..cbf3abe24cd 100644 --- a/fs/ocfs2/dlm/dlmmaster.c +++ b/fs/ocfs2/dlm/dlmmaster.c @@ -505,8 +505,10 @@ void dlm_change_lockres_owner(struct dlm_ctxt *dlm, static void dlm_lockres_release(struct kref *kref) { struct dlm_lock_resource *res; + struct dlm_ctxt *dlm; res = container_of(kref, struct dlm_lock_resource, refs); + dlm = res->dlm; /* This should not happen -- all lockres' have a name * associated with them at init time. */ @@ -515,6 +517,7 @@ static void dlm_lockres_release(struct kref *kref) mlog(0, "destroying lockres %.*s\n", res->lockname.len, res->lockname.name); + spin_lock(&dlm->track_lock); if (!list_empty(&res->tracking)) list_del_init(&res->tracking); else { @@ -522,6 +525,9 @@ static void dlm_lockres_release(struct kref *kref) res->lockname.len, res->lockname.name); dlm_print_one_lock_resource(res); } + spin_unlock(&dlm->track_lock); + + dlm_put(dlm); if (!hlist_unhashed(&res->hash_node) || !list_empty(&res->granted) || @@ -595,6 +601,10 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm, res->migration_pending = 0; res->inflight_locks = 0; + /* put in dlm_lockres_release */ + dlm_grab(dlm); + res->dlm = dlm; + kref_init(&res->refs); /* just for consistency */ -- cgit v1.2.3-18-g5258