linux-kernel - Re: [RFC 7/7] rv: add dlm compatible lock state kernel verifier

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Message-ID: <CAK-6q+iedvC_b3_dO+7C6S15y2o9uuqwDaNJ=a0wZE3hW=+G1g@mail.gmail.com>
Date: Fri, 30 Aug 2024 08:55:31 -0400
From: Alexander Aring <aahringo@...hat.com>
To: teigland@...hat.com
Cc: gfs2@...ts.linux.dev, song@...nel.org, yukuai3@...wei.com, 
	agruenba@...hat.com, mark@...heh.com, jlbec@...lplan.org, 
	joseph.qi@...ux.alibaba.com, gregkh@...uxfoundation.org, rafael@...nel.org, 
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, 
	linux-raid@...r.kernel.org, ocfs2-devel@...ts.linux.dev, 
	netdev@...r.kernel.org, vvidic@...entin-vidic.from.hr, heming.zhao@...e.com, 
	lucien.xin@...il.com, paulmck@...nel.org, rcu@...r.kernel.org, 
	juri.lelli@...hat.com, williams@...hat.com
Subject: Re: [RFC 7/7] rv: add dlm compatible lock state kernel verifier

Hi,

On Tue, Aug 27, 2024 at 2:03 PM Alexander Aring <aahringo@...hat.com> wrote:
...
> +       set_holder_state(lk, our_nodeid, mode);
> +       rv = check_valid_lock_holders(lk, mode, our_nodeid);
> +       if (rv) {
> +               /* the whole validation process, this event signals
> +                * everything is fine and DLM works correctly there
> +                * are no cluster-wide locks that violates DLM locking.
> +                */
> +               da_handle_event_dlm(lk, with_others_compatible_dlm);
> +       } else {
> +               /* print all holders of the lock when a invalid lock state is entered */
> +               console_lock();

I can't hold this lock in some contexts the ast callback can be called from.
I will drop this lock as I don't care.

It would be nice to use this msg callback from the refactor but then I
somehow need to pass the lk pointer to it.

This however works for me that I know at least which nodes/modes are
incompatible if it hits.

> +               pr_info("---\n");
> +               pr_info("ls_id %u lkb_id: 0x%08x\n", ls_id, lkb_id);
> +               pr_info("holders:\n");
> +               list_for_each_entry(hl, &lk->holders, list) {
> +                       pr_info("\tnodeid: %u mode: %d\n", hl->nodeid,
> +                               hl->mode);
> +               }
> +               pr_info("---\n");
> +               console_unlock();
> +
> +               /* move into an invalid state change, we don't have a edge for that
> +                * so we just use event_max_dlm.
> +                */
> +               da_handle_event_dlm(lk, event_max_dlm);
> +       }
> +       spin_unlock_bh(&dlm_rv_hash_lock);
> +}
> +
> +/* set the holder to transition state as lock downgrades can issue
> + * grant messages to other nodes we need to ignore if a lock on a
> + * specific node is in state transition. From point of DLM API
> + * the user cannot assume to still hold the lock at this point
> + * anyway.
> + */
> +static void set_holder_transition(uint32_t ls_id, const char *res_name,
> +                                 size_t res_length, uint32_t our_nodeid)
> +{
> +       struct dlm_rv_holder *hl;
> +       struct dlm_rv_lock *lk;
> +
> +       spin_lock_bh(&dlm_rv_hash_lock);
> +       lk = lookup_lock(ls_id, res_name, res_length);
> +       if (lk) {
> +               hl = lookup_holder(lk, our_nodeid);
> +               if (hl)
> +                       hl->mode = STATE_MODE_IN_TRANSITION;
> +       }
> +       spin_unlock_bh(&dlm_rv_hash_lock);
> +}
> +
> +/* after a lock request got validated it cannot fail */
> +static void handle_dlm_lock_validated(void *data, struct dlm_ls *ls,
> +                                     struct dlm_lkb *lkb,
> +                                     struct dlm_args *args,
> +                                     const char *res_name, size_t res_length)
> +{
> +       set_holder_transition(ls->ls_global_id, res_name,
> +                             res_length, ls->ls_dn->our_node->id);
> +}
> +
> +static void handle_dlm_unlock_validated(void *data, struct dlm_ls *ls,
> +                                       struct dlm_lkb *lkb,
> +                                       struct dlm_args *args)
> +{

we need to ignore unlock(CANCEL) requests.

> +       set_holder_transition(ls->ls_global_id,
> +                             lkb->lkb_resource->res_name,
> +                             lkb->lkb_resource->res_length,
> +                             ls->ls_dn->our_node->id);
> +}
> +

- Alex