Good that there's no penalty for single node mirroring.
ACK
Heinz
Am Freitag, den 09.01.2009, 12:14 -0600 schrieb Jonathan Brassow:
> This patch is the same patch as posted in a previous e-mail. I am
> reposting so that it gets into Patchwork. The patch for "cluster-aware
> logging module" depends on this.
>
> brassow
>
> The logging API needs an extra function to make cluster mirroring
> possible. This new function allows us to check whether a mirror
> region is being recovered on another machine in the cluster. This
> helps us prevent simultaneous recovery I/O and process I/O to the
> same locations on disk.
>
> Cluster-aware log modules will implement this function. Single
> machine log modules will not. So, there is no performance
> penalty for single machine mirrors.
>
> Signed-off-by: Jonathan Brassow <jbrassow@xxxxxxxxxx>
>
> Index: linux-2.6/drivers/md/dm-raid1.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-raid1.c
> +++ linux-2.6/drivers/md/dm-raid1.c
> @@ -586,6 +586,9 @@ static void do_writes(struct mirror_set
> int state;
> struct bio *bio;
> struct bio_list sync, nosync, recover, *this_list = NULL;
> + struct bio_list requeue;
> + struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
> + region_t region;
>
> if (!writes->head)
> return;
> @@ -596,10 +599,18 @@ static void do_writes(struct mirror_set
> bio_list_init(&sync);
> bio_list_init(&nosync);
> bio_list_init(&recover);
> + bio_list_init(&requeue);
>
> while ((bio = bio_list_pop(writes))) {
> - state = dm_rh_get_state(ms->rh,
> - dm_rh_bio_to_region(ms->rh, bio), 1);
> + region = dm_rh_bio_to_region(ms->rh, bio);
> +
> + if (log->type->is_remote_recovering &&
> + log->type->is_remote_recovering(log, region)) {
> + bio_list_add(&requeue, bio);
> + continue;
> + }
> +
> + state = dm_rh_get_state(ms->rh, region, 1);
> switch (state) {
> case DM_RH_CLEAN:
> case DM_RH_DIRTY:
> @@ -619,6 +630,16 @@ static void do_writes(struct mirror_set
> }
>
> /*
> + * Add bios that are delayed due to remote recovery
> + * back on to the write queue
> + */
> + if (unlikely(requeue.head)) {
> + spin_lock_irq(&ms->lock);
> + bio_list_merge(&ms->writes, &requeue);
> + spin_unlock_irq(&ms->lock);
> + }
> +
> + /*
> * Increment the pending counts for any regions that will
> * be written to (writes to recover regions are going to
> * be delayed).
> Index: linux-2.6/include/linux/dm-dirty-log.h
> ===================================================================
> --- linux-2.6.orig/include/linux/dm-dirty-log.h
> +++ linux-2.6/include/linux/dm-dirty-log.h
> @@ -113,6 +113,16 @@ struct dm_dirty_log_type {
> */
> int (*status)(struct dm_dirty_log *log, status_type_t status_type,
> char *result, unsigned maxlen);
> +
> + /*
> + * is_remote_recovering is necessary for cluster mirroring. It provides
> + * a way to detect recovery on another node, so we aren't writing
> + * concurrently. This function is likely to block (when a cluster log
> + * is used).
> + *
> + * Returns: 0, 1
> + */
> + int (*is_remote_recovering)(struct dm_dirty_log *log, region_t region);
> };
>
> int dm_dirty_log_type_register(struct dm_dirty_log_type *type);
>
>
> --
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> dm-devel@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/dm-devel
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