From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joseph Qi Date: Thu, 24 Sep 2015 12:11:56 +0800 Subject: [Ocfs2-devel] [PATCH 1/2 v3] ocfs2/dlm: fix race between convert and recovery In-Reply-To: <560374F4.10307@oracle.com> References: <56036AAB.7070102@huawei.com> <560374F4.10307@oracle.com> Message-ID: <5603780C.2040400@huawei.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Hi Junxiao, On 2015/9/24 11:58, Junxiao Bi wrote: > On 09/24/2015 11:14 AM, Joseph Qi wrote: >> There is a race window between dlmconvert_remote and >> dlm_move_lockres_to_recovery_list, which will cause a lock with >> OCFS2_LOCK_BUSY in grant list, thus system hangs. >> >> dlmconvert_remote >> { >> spin_lock(&res->spinlock); >> list_move_tail(&lock->list, &res->converting); >> lock->convert_pending = 1; >> spin_unlock(&res->spinlock); >> >> status = dlm_send_remote_convert_request(); >> >>>>>> race window, master has queued ast and return DLM_NORMAL, >> and then down before sending ast. >> this node detects master down and calls >> dlm_move_lockres_to_recovery_list, which will revert the >> lock to grant list. >> Then OCFS2_LOCK_BUSY won't be cleared as new master won't >> send ast any more because it thinks already be authorized. > How this race windowed fixed? > the process have sent convert request to master node successfully(return > value DLM_NORMAL) then wait on LOCK_BUSY, then when master node panic > before send out ast, dlm_move_lockres_to_recovery_list() move the lock > to grant list. Ast never come. res->state is now having DLM_LOCK_RES_RECOVERING set. This patch will reset the status to DLM_RECOVERING and then retry convert request. Then new master will handle it and send ast. > > Thanks, > Junxiao. > >> >> spin_lock(&res->spinlock); >> lock->convert_pending = 0; >> if (status != DLM_NORMAL) >> dlm_revert_pending_convert(res, lock); >> spin_unlock(&res->spinlock); >> } >> >> In this case, check if res->state has DLM_LOCK_RES_RECOVERING bit set >> (res is still in recovering) or res master changed (new master has >> finished recovery), reset the status to DLM_RECOVERING, then it will >> retry convert. >> >> Signed-off-by: Joseph Qi >> Reported-by: Yiwen Jiang >> Cc: >> --- >> fs/ocfs2/dlm/dlmconvert.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c >> index e36d63f..9e6116e 100644 >> --- a/fs/ocfs2/dlm/dlmconvert.c >> +++ b/fs/ocfs2/dlm/dlmconvert.c >> @@ -262,6 +262,7 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm, >> struct dlm_lock *lock, int flags, int type) >> { >> enum dlm_status status; >> + u8 old_owner = res->owner; >> >> mlog(0, "type=%d, convert_type=%d, busy=%d\n", lock->ml.type, >> lock->ml.convert_type, res->state & DLM_LOCK_RES_IN_PROGRESS); >> @@ -316,11 +317,19 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm, >> spin_lock(&res->spinlock); >> res->state &= ~DLM_LOCK_RES_IN_PROGRESS; >> lock->convert_pending = 0; >> - /* if it failed, move it back to granted queue */ >> + /* if it failed, move it back to granted queue. >> + * if master returns DLM_NORMAL and then down before sending ast, >> + * it may have already been moved to granted queue, reset to >> + * DLM_RECOVERING and retry convert */ >> if (status != DLM_NORMAL) { >> if (status != DLM_NOTQUEUED) >> dlm_error(status); >> dlm_revert_pending_convert(res, lock); >> + } else if ((res->state & DLM_LOCK_RES_RECOVERING) || >> + (old_owner != res->owner)) { >> + mlog(0, "res %.*s is in recovering or has been recovered.\n", >> + res->lockname.len, res->lockname.name); >> + status = DLM_RECOVERING; >> } >> bail: >> spin_unlock(&res->spinlock); >> > > > . >