Mark Fasheh wrote: > On Tue, Dec 16, 2008 at 03:49:23PM -0800, Sunil Mushran wrote: > >> 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. >> >> Patch fixes Novell bz#425491 >> https://bugzilla.novell.com/show_bug.cgi?id=425491 >> >> 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 <[email protected]> >> Signed-off-by: Sunil Mushran <[email protected]> >> --- >> fs/ocfs2/dlm/dlmmaster.c | 9 ++++++++- >> 1 files changed, 8 insertions(+), 1 deletions(-) >> >> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c >> index cbf3abe..54e182a 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); >> + } >> > > Do we have a ref on tmpres here, when we decide to wait on it? Could it get > destroyed during mastery (for example, due to mastery ending in error) and > we wake up with a bad pointer? > Yes. __dlm_lookup_lockres_full() takes a reference.
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