[Ocfs2-devel] [PATCH] ocfs2/dlm: retry migrating if nomem or lockres is in recovery on target
Sunil Mushran
sunil.mushran at oracle.com
Thu Sep 9 18:41:46 PDT 2010
I don't think this fixes the issue. As in, the fix for reco+mig race is a
lot more involved. Is someone hitting this freq? As in, this should be
a hard race to reproduce.
On 08/31/2010 08:41 AM, Wengang Wang wrote:
> This patch tries to fix two problems:
>
> problem 1):
> It's a case of recovery + migration. That is a recovery is happening when node I
> is in progress of umount. Node I is the recovery master.
> Say lockres A was mastered by the dead node and need to be recovered. Node I(the
> reco master) and node II both have reference on lockres A.
> So lockres A is being recovered from node II to node I, with RECOVERING flag set.
> The umounting process is going on, it happened to be migrating lockres A to node
> II. Since recovery not finished yet(RECOVERING still set), node II reponds with
> -EFAULT to kill node I. Then node I killed its self(BUGON).
>
> There is a checking for recovery(on RECOVERING), but it droped res->spinlock and
> dlm->spinlock. So the checking does not help much enough.
>
> Since we have to drop any spinlock when we are sending migrate lockres(
> DLM_MIG_LOCKRES_MSG) message, we have to deal with above case.
>
> problem 2):
> In the same context of problem 1), -ENOMEM from target node can trigger an
> incorrect BUG() on the requester of "migrate lockres".
>
> The fix is when target node returns -EFAULT or -ENOMEM, we retry the migration(
> for umount).
> Though they are two separated problems, the fixes are in the same way. So I
> combined them together.
>
> Signed-off-by: Wengang Wang<wen.gang.wang at oracle.com>
> ---
> fs/ocfs2/dlm/dlmrecovery.c | 28 ++++++++++++++++++++++------
> 1 files changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
> index aaaffbc..b7dd03f 100644
> --- a/fs/ocfs2/dlm/dlmrecovery.c
> +++ b/fs/ocfs2/dlm/dlmrecovery.c
> @@ -1122,6 +1122,8 @@ static int dlm_send_mig_lockres_msg(struct dlm_ctxt *dlm,
> orig_flags& DLM_MRES_MIGRATION ? "migration" : "recovery",
> send_to);
>
> +#define WAIT_FOR_NOMEM_MS 30
> +resend:
> /* send it */
> ret = o2net_send_message(DLM_MIG_LOCKRES_MSG, dlm->key, mres,
> sz, send_to,&status);
> @@ -1132,16 +1134,30 @@ static int dlm_send_mig_lockres_msg(struct dlm_ctxt *dlm,
> "0x%x) to node %u\n", ret, DLM_MIG_LOCKRES_MSG,
> dlm->key, send_to);
> } else {
> - /* might get an -ENOMEM back here */
> - ret = status;
> if (ret< 0) {
> mlog_errno(ret);
>
> - if (ret == -EFAULT) {
> - mlog(ML_ERROR, "node %u told me to kill "
> - "myself!\n", send_to);
> - BUG();
> + /*
> + * -ENOMEM or -EFAULT here.
> + * -EFAULT means lockres is in recovery.
> + * we should retry in both the two cases.
> + */
> + ret = status;
> + if (ret == -ENOMEM) {
> + mlog(ML_NOTICE, "node %u no memory\n",
> + send_to);
> + if (dlm_in_recovery(dlm)) {
> + dlm_wait_for_recovery(dlm);
> + } else {
> + msleep(WAIT_FOR_NOMEM_MS);
> + }
> + } else {
> + BUG_ON(ret != -EFAULT);
> + mlog(ML_NOTICE, "node %u in recovery\n",
> + send_to);
> + dlm_wait_for_recovery(dlm);
> }
> + goto resend;
> }
> }
>
>
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