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authorSunil Mushran <sunil.mushran@oracle.com>2008-12-16 15:49:23 -0800
committerMark Fasheh <mfasheh@suse.com>2009-01-05 08:40:35 -0800
commit7b791d68562e4ce5ab57cbacb10a1ad4ee33956e (patch)
tree7ecff8f244995c4d16dff21f2a61c9946ab67435
parentb0d4f817ba5de8adb875ace594554a96d7737710 (diff)
ocfs2/dlm: Fix race during lockres mastery
dlm_get_lock_resource() is supposed to return a lock resource with a proper master. If multiple concurrent threads attempt to lookup the lockres for the same lockid while the lock mastery in underway, one or more threads are likely to return a lockres without a proper master. This patch makes the threads wait in dlm_get_lock_resource() while the mastery is underway, ensuring all threads return the lockres with a proper master. This issue is known to be limited to users using the flock() syscall. For all other fs operations, the ocfs2 dlmglue layer serializes the dlm op for each lockid. Users encountering this bug will see flock() return EINVAL and dmesg have the following error: ERROR: Dlm error "DLM_BADARGS" while calling dlmlock on resource <LOCKID>: bad api args Reported-by: Coly Li <coyli@suse.de> Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
-rw-r--r--fs/ocfs2/dlm/dlmmaster.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index cbf3abe24cd..54e182a27ca 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -732,14 +732,21 @@ lookup:
if (tmpres) {
int dropping_ref = 0;
+ spin_unlock(&dlm->spinlock);
+
spin_lock(&tmpres->spinlock);
+ /* We wait for the other thread that is mastering the resource */
+ if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
+ __dlm_wait_on_lockres(tmpres);
+ BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
+ }
+
if (tmpres->owner == dlm->node_num) {
BUG_ON(tmpres->state & DLM_LOCK_RES_DROPPING_REF);
dlm_lockres_grab_inflight_ref(dlm, tmpres);
} else if (tmpres->state & DLM_LOCK_RES_DROPPING_REF)
dropping_ref = 1;
spin_unlock(&tmpres->spinlock);
- spin_unlock(&dlm->spinlock);
/* wait until done messaging the master, drop our ref to allow
* the lockres to be purged, start over. */