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authorNeilBrown <neilb@suse.de>2009-03-31 00:28:40 -0400
committerNeilBrown <neilb@suse.de>2009-03-31 00:28:40 -0400
commitc8f517c444e4f9f55b5b5ca202b8404691a35805 (patch)
treee679ae13a07e1a2644da0dfc4a4d66bf73f83626 /drivers/md/raid5.h
parentb0f9ec047b79a92e8b8a9dfbf97537c8fbef234a (diff)
md/raid5 revise rules for when to update metadata during reshape
We currently update the metadata : 1/ every 3Megabytes 2/ When the place we will write new-layout data to is recorded in the metadata as still containing old-layout data. Rule one exists to avoid having to re-do too much reshaping in the face of a crash/restart. So it should really be time based rather than size based. So change it to "every 10 seconds". Rule two turns out to be too harsh when restriping an array 'in-place', as in that case the metadata much be updates for every stripe. For the in-place update, it can only possibly be safe from a crash if some user-space program data a backup of every e.g. few hundred stripes before allowing them to be reshaped. In that case, the constant metadata update is pointless. So only update the metadata if the new metadata will report that the end of the 'old-layout' data is beyond where we are currently writing 'new-layout' data. Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/raid5.h')
-rw-r--r--drivers/md/raid5.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index cdd045681720..52ba99954dec 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -352,6 +352,8 @@ struct raid5_private_data {
352 int previous_raid_disks; 352 int previous_raid_disks;
353 int prev_chunk, prev_algo; 353 int prev_chunk, prev_algo;
354 short generation; /* increments with every reshape */ 354 short generation; /* increments with every reshape */
355 unsigned long reshape_checkpoint; /* Time we last updated
356 * metadata */
355 357
356 struct list_head handle_list; /* stripes needing handling */ 358 struct list_head handle_list; /* stripes needing handling */
357 struct list_head hold_list; /* preread ready stripes */ 359 struct list_head hold_list; /* preread ready stripes */