On ven., 2012-07-27 at 15:56 -0500, Benjamin Marzinski wrote:
> This patch adds a new failback mode, followover, to deal with multiple
> computers accessing the same active/passive storage devices. In these
> cases, if only one node loses access to the primary paths, it will
> force a trespass to the secondary paths. If the nodes are configured
> with immediate failback, the other nodes with trespass back to the
> primary paths, and the machines will ping-pong the storage. If the
> nodes are configured with manual failback, this won't happen. However
> when the primary path is restored on the node that lost access to it,
> the nodes won't automatically failback to it. In followover mode, they
> will.
>
> Followover mode works by only failing back when a path comes back online
> from a pathgroup that previously had no working paths. For this to
> work, the paths need an additional attribute, chkrstate. This is just like
> the path state, except it is not updated when the paths state is changed
> by the kernel, only when the path checker function sees that the path is
> down. This is necessary because when a trespass occurs, all the outstanding
> IO to the previously active paths will fail, and the kernel will mark the
> path as down. But for failback to happen in followover mode, the paths must
> actually be down, not just in a ghost state.
>
Applied.
Good feature indeed.
> Signed-off-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
> ---
> libmultipath/dict.c | 12 ++++++++++++
> libmultipath/discovery.c | 6 +++---
> libmultipath/print.c | 2 ++
> libmultipath/structs.h | 4 +++-
> multipath/main.c | 2 +-
> multipath/multipath.conf.5 | 5 +++++
> multipathd/main.c | 35 ++++++++++++++++++++++++++++++++++-
> 7 files changed, 60 insertions(+), 6 deletions(-)
>
> Index: multipath-tools-120518/libmultipath/dict.c
> ===================================================================
> --- multipath-tools-120518.orig/libmultipath/dict.c
> +++ multipath-tools-120518/libmultipath/dict.c
> @@ -398,6 +398,8 @@ default_failback_handler(vector strvec)
> conf->pgfailback = -FAILBACK_MANUAL;
> else if (strlen(buff) == 9 && !strcmp(buff, "immediate"))
> conf->pgfailback = -FAILBACK_IMMEDIATE;
> + else if (strlen(buff) == 10 && !strcmp(buff, "followover"))
> + conf->pgfailback = -FAILBACK_FOLLOWOVER;
> else
> conf->pgfailback = atoi(buff);
>
> @@ -1053,6 +1055,8 @@ hw_failback_handler(vector strvec)
> hwe->pgfailback = -FAILBACK_MANUAL;
> else if (strlen(buff) == 9 && !strcmp(buff, "immediate"))
> hwe->pgfailback = -FAILBACK_IMMEDIATE;
> + else if (strlen(buff) == 10 && !strcmp(buff, "followover"))
> + hwe->pgfailback = -FAILBACK_FOLLOWOVER;
> else
> hwe->pgfailback = atoi(buff);
>
> @@ -1351,6 +1355,8 @@ mp_failback_handler(vector strvec)
> mpe->pgfailback = -FAILBACK_MANUAL;
> else if (strlen(buff) == 9 && !strcmp(buff, "immediate"))
> mpe->pgfailback = -FAILBACK_IMMEDIATE;
> + else if (strlen(buff) == 10 && !strcmp(buff, "followover"))
> + mpe->pgfailback = -FAILBACK_FOLLOWOVER;
> else
> mpe->pgfailback = atoi(buff);
>
> @@ -1769,6 +1775,8 @@ snprint_mp_failback (char * buff, int le
> return snprintf(buff, len, "manual");
> case -FAILBACK_IMMEDIATE:
> return snprintf(buff, len, "immediate");
> + case -FAILBACK_FOLLOWOVER:
> + return snprintf(buff, len, "followover");
> default:
> return snprintf(buff, len, "%i", mpe->pgfailback);
> }
> @@ -2130,6 +2138,8 @@ snprint_hw_failback (char * buff, int le
> return snprintf(buff, len, "manual");
> case -FAILBACK_IMMEDIATE:
> return snprintf(buff, len, "immediate");
> + case -FAILBACK_FOLLOWOVER:
> + return snprintf(buff, len, "followover");
> default:
> return snprintf(buff, len, "%i", hwe->pgfailback);
> }
> @@ -2394,6 +2404,8 @@ snprint_def_failback (char * buff, int l
> return snprintf(buff, len, "manual");
> case -FAILBACK_IMMEDIATE:
> return snprintf(buff, len, "immediate");
> + case -FAILBACK_FOLLOWOVER:
> + return snprintf(buff, len, "followover");
> default:
> return snprintf(buff, len, "%i", conf->pgfailback);
> }
> Index: multipath-tools-120518/libmultipath/print.c
> ===================================================================
> --- multipath-tools-120518.orig/libmultipath/print.c
> +++ multipath-tools-120518/libmultipath/print.c
> @@ -143,6 +143,8 @@ snprint_failback (char * buff, size_t le
> {
> if (mpp->pgfailback == -FAILBACK_IMMEDIATE)
> return snprintf(buff, len, "immediate");
> + if (mpp->pgfailback == -FAILBACK_FOLLOWOVER)
> + return snprintf(buff, len, "followover");
>
> if (!mpp->failback_tick)
> return snprintf(buff, len, "-");
> Index: multipath-tools-120518/libmultipath/structs.h
> ===================================================================
> --- multipath-tools-120518.orig/libmultipath/structs.h
> +++ multipath-tools-120518/libmultipath/structs.h
> @@ -39,7 +39,8 @@ enum rr_weight_mode {
> enum failback_mode {
> FAILBACK_UNDEF,
> FAILBACK_MANUAL,
> - FAILBACK_IMMEDIATE
> + FAILBACK_IMMEDIATE,
> + FAILBACK_FOLLOWOVER
> };
>
> enum sysfs_buses {
> @@ -151,6 +152,7 @@ struct path {
> int offline;
> int state;
> int dmstate;
> + int chkrstate;
> int failcount;
> int priority;
> int pgindex;
> Index: multipath-tools-120518/multipathd/main.c
> ===================================================================
> --- multipath-tools-120518.orig/multipathd/main.c
> +++ multipath-tools-120518/multipathd/main.c
> @@ -995,6 +995,32 @@ mpvec_garbage_collector (struct vectors
> }
> }
>
> +/* This is called after a path has started working again. It the multipath
> + * device for this path uses the followover failback type, and this is the
> + * best pathgroup, and this is the first path in the pathgroup to come back
> + * up, then switch to this pathgroup */
> +static int
> +followover_should_failback(struct path * pp)
> +{
> + struct pathgroup * pgp;
> + struct path *pp1;
> + int i;
> +
> + if (pp->mpp->pgfailback != -FAILBACK_FOLLOWOVER ||
> + !pp->mpp->pg || !pp->pgindex ||
> + pp->pgindex != pp->mpp->bestpg)
> + return 0;
> +
> + pgp = VECTOR_SLOT(pp->mpp->pg, pp->pgindex - 1);
> + vector_foreach_slot(pgp->paths, pp1, i) {
> + if (pp1 == pp)
> + continue;
> + if (pp1->chkrstate != PATH_DOWN && pp1->chkrstate != PATH_SHAKY)
> + return 0;
> + }
> + return 1;
> +}
> +
> static void
> defered_failback_tick (vector mpvec)
> {
> @@ -1092,6 +1118,8 @@ check_path (struct vectors * vecs, struc
> {
> int newstate;
> int new_path_up = 0;
> + int chkr_new_path_up = 0;
> + int oldchkrstate = pp->chkrstate;
>
> if (!pp->mpp)
> return;
> @@ -1130,6 +1158,7 @@ check_path (struct vectors * vecs, struc
> pp->dev);
> pp->dmstate = PSTATE_UNDEF;
> }
> + pp->chkrstate = newstate;
> if (newstate != pp->state) {
> int oldstate = pp->state;
> pp->state = newstate;
> @@ -1182,6 +1211,9 @@ check_path (struct vectors * vecs, struc
>
> new_path_up = 1;
>
> + if (oldchkrstate != PATH_UP && oldchkrstate != PATH_GHOST)
> + chkr_new_path_up = 1;
> +
> /*
> * if at least one path is up in a group, and
> * the group is disabled, re-enable it
> @@ -1233,7 +1265,8 @@ check_path (struct vectors * vecs, struc
> (new_path_up || pp->mpp->failback_tick <= 0))
> pp->mpp->failback_tick =
> pp->mpp->pgfailback + 1;
> - else if (pp->mpp->pgfailback == -FAILBACK_IMMEDIATE)
> + else if (pp->mpp->pgfailback == -FAILBACK_IMMEDIATE ||
> + (chkr_new_path_up && followover_should_failback(pp)))
> switch_pathgroup(pp->mpp);
> }
> }
> Index: multipath-tools-120518/multipath/multipath.conf.5
> ===================================================================
> --- multipath-tools-120518.orig/multipath/multipath.conf.5
> +++ multipath-tools-120518/multipath/multipath.conf.5
> @@ -254,6 +254,11 @@ active paths.
> .B manual
> Do not perform automatic failback.
> .TP
> +.B followover
> +Only perform automatic failback when the first path of a pathgroup
> +becomes active. This keeps a node from automatically failing back when
> +another node requested the failover.
> +.TP
> .B values > 0
> deferred failback (time to defer in seconds)
> .TP
> Index: multipath-tools-120518/libmultipath/discovery.c
> ===================================================================
> --- multipath-tools-120518.orig/libmultipath/discovery.c
> +++ multipath-tools-120518/libmultipath/discovery.c
> @@ -878,13 +878,13 @@ pathinfo (struct path *pp, vector hwtabl
>
> if (mask & DI_CHECKER) {
> if (path_state == PATH_UP) {
> - pp->state = get_state(pp, 0);
> + pp->chkrstate = pp->state = get_state(pp, 0);
> if (pp->state == PATH_UNCHECKED ||
> pp->state == PATH_WILD)
> goto blank;
> } else {
> condlog(3, "%s: path inaccessible", pp->dev);
> - pp->state = path_state;
> + pp->chkrstate = pp->state = path_state;
> }
> }
>
> @@ -912,7 +912,7 @@ blank:
> * Recoverable error, for example faulty or offline path
> */
> memset(pp->wwid, 0, WWID_SIZE);
> - pp->state = PATH_DOWN;
> + pp->chkrstate = pp->state = PATH_DOWN;
>
> return 0;
> }
> Index: multipath-tools-120518/multipath/main.c
> ===================================================================
> --- multipath-tools-120518.orig/multipath/main.c
> +++ multipath-tools-120518/multipath/main.c
> @@ -144,7 +144,7 @@ update_paths (struct multipath * mpp)
> /*
> * path is not in sysfs anymore
> */
> - pp->state = PATH_DOWN;
> + pp->chkrstate = pp->state = PATH_DOWN;
> continue;
> }
> pp->mpp = mpp;
--
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