diff options
Diffstat (limited to 'fs/dlm/lock.c')
| -rw-r--r-- | fs/dlm/lock.c | 78 |
1 files changed, 58 insertions, 20 deletions
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c index 6dca5cdbbc5d..fd752dd03896 100644 --- a/fs/dlm/lock.c +++ b/fs/dlm/lock.c @@ -5014,21 +5014,32 @@ static struct dlm_lkb *find_resend_waiter(struct dlm_ls *ls) return lkb; } -/* Deal with lookups and lkb's marked RESEND from _pre. We may now be the - master or dir-node for r. Processing the lkb may result in it being placed - back on waiters. */ - -/* We do this after normal locking has been enabled and any saved messages - (in requestqueue) have been processed. We should be confident that at - this point we won't get or process a reply to any of these waiting - operations. But, new ops may be coming in on the rsbs/locks here from - userspace or remotely. */ - -/* there may have been an overlap unlock/cancel prior to recovery or after - recovery. if before, the lkb may still have a pos wait_count; if after, the - overlap flag would just have been set and nothing new sent. we can be - confident here than any replies to either the initial op or overlap ops - prior to recovery have been received. */ +/* + * Forced state reset for locks that were in the middle of remote operations + * when recovery happened (i.e. lkbs that were on the waiters list, waiting + * for a reply from a remote operation.) The lkbs remaining on the waiters + * list need to be reevaluated; some may need resending to a different node + * than previously, and some may now need local handling rather than remote. + * + * First, the lkb state for the voided remote operation is forcibly reset, + * equivalent to what remove_from_waiters() would normally do: + * . lkb removed from ls_waiters list + * . lkb wait_type cleared + * . lkb waiters_count cleared + * . lkb ref count decremented for each waiters_count (almost always 1, + * but possibly 2 in case of cancel/unlock overlapping, which means + * two remote replies were being expected for the lkb.) + * + * Second, the lkb is reprocessed like an original operation would be, + * by passing it to _request_lock or _convert_lock, which will either + * process the lkb operation locally, or send it to a remote node again + * and put the lkb back onto the waiters list. + * + * When reprocessing the lkb, we may find that it's flagged for an overlapping + * force-unlock or cancel, either from before recovery began, or after recovery + * finished. If this is the case, the unlock/cancel is done directly, and the + * original operation is not initiated again (no _request_lock/_convert_lock.) + */ int dlm_recover_waiters_post(struct dlm_ls *ls) { @@ -5043,6 +5054,11 @@ int dlm_recover_waiters_post(struct dlm_ls *ls) break; } + /* + * Find an lkb from the waiters list that's been affected by + * recovery node changes, and needs to be reprocessed. Does + * hold_lkb(), adding a refcount. + */ lkb = find_resend_waiter(ls); if (!lkb) break; @@ -5051,6 +5067,11 @@ int dlm_recover_waiters_post(struct dlm_ls *ls) hold_rsb(r); lock_rsb(r); + /* + * If the lkb has been flagged for a force unlock or cancel, + * then the reprocessing below will be replaced by just doing + * the unlock/cancel directly. + */ mstype = lkb->lkb_wait_type; oc = test_and_clear_bit(DLM_IFL_OVERLAP_CANCEL_BIT, &lkb->lkb_iflags); @@ -5064,23 +5085,40 @@ int dlm_recover_waiters_post(struct dlm_ls *ls) r->res_nodeid, lkb->lkb_nodeid, lkb->lkb_wait_nodeid, dlm_dir_nodeid(r), oc, ou); - /* At this point we assume that we won't get a reply to any - previous op or overlap op on this lock. First, do a big - remove_from_waiters() for all previous ops. */ + /* + * No reply to the pre-recovery operation will now be received, + * so a forced equivalent of remove_from_waiters() is needed to + * reset the waiters state that was in place before recovery. + */ clear_bit(DLM_IFL_RESEND_BIT, &lkb->lkb_iflags); + + /* Forcibly clear wait_type */ lkb->lkb_wait_type = 0; - /* drop all wait_count references we still - * hold a reference for this iteration. + + /* + * Forcibly reset wait_count and associated refcount. The + * wait_count will almost always be 1, but in case of an + * overlapping unlock/cancel it could be 2: see where + * add_to_waiters() finds the lkb is already on the waiters + * list and does lkb_wait_count++; hold_lkb(). */ while (lkb->lkb_wait_count) { lkb->lkb_wait_count--; unhold_lkb(lkb); } + + /* Forcibly remove from waiters list */ mutex_lock(&ls->ls_waiters_mutex); list_del_init(&lkb->lkb_wait_reply); mutex_unlock(&ls->ls_waiters_mutex); + /* + * The lkb is now clear of all prior waiters state and can be + * processed locally, or sent to remote node again, or directly + * cancelled/unlocked. + */ + if (oc || ou) { /* do an unlock or cancel instead of resending */ switch (mstype) { |