[PATCH] md: Don't write dirty/clean update to spares - leave them alone
- record the 'event' count on each individual device (they
might sometimes be slightly different now)
- add a new value for 'sb_dirty': '3' means that the super
block only needs to be updated to record a clean<->dirty
transition.
- Prefer odd event numbers for dirty states and even numbers
for clean states
- Using all the above, don't update the superblock on
a spare device if the update is just doing a clean-dirty
transition. To accomodate this, a transition from
dirty back to clean might now decrement the events counter
if nothing else has changed.
The net effect of this is that spare drives will not see any IO requests
during normal running of the array, so they can go to sleep if that is what
they want to do.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6f97817..34b6902 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1558,15 +1558,30 @@
}
-static void sync_sbs(mddev_t * mddev)
+static void sync_sbs(mddev_t * mddev, int nospares)
{
+ /* Update each superblock (in-memory image), but
+ * if we are allowed to, skip spares which already
+ * have the right event counter, or have one earlier
+ * (which would mean they aren't being marked as dirty
+ * with the rest of the array)
+ */
mdk_rdev_t *rdev;
struct list_head *tmp;
ITERATE_RDEV(mddev,rdev,tmp) {
- super_types[mddev->major_version].
- sync_super(mddev, rdev);
- rdev->sb_loaded = 1;
+ if (rdev->sb_events == mddev->events ||
+ (nospares &&
+ rdev->raid_disk < 0 &&
+ (rdev->sb_events&1)==0 &&
+ rdev->sb_events+1 == mddev->events)) {
+ /* Don't update this superblock */
+ rdev->sb_loaded = 2;
+ } else {
+ super_types[mddev->major_version].
+ sync_super(mddev, rdev);
+ rdev->sb_loaded = 1;
+ }
}
}
@@ -1576,12 +1591,42 @@
struct list_head *tmp;
mdk_rdev_t *rdev;
int sync_req;
+ int nospares = 0;
repeat:
spin_lock_irq(&mddev->write_lock);
sync_req = mddev->in_sync;
mddev->utime = get_seconds();
- mddev->events ++;
+ if (mddev->sb_dirty == 3)
+ /* just a clean<-> dirty transition, possibly leave spares alone,
+ * though if events isn't the right even/odd, we will have to do
+ * spares after all
+ */
+ nospares = 1;
+
+ /* If this is just a dirty<->clean transition, and the array is clean
+ * and 'events' is odd, we can roll back to the previous clean state */
+ if (mddev->sb_dirty == 3
+ && (mddev->in_sync && mddev->recovery_cp == MaxSector)
+ && (mddev->events & 1))
+ mddev->events--;
+ else {
+ /* otherwise we have to go forward and ... */
+ mddev->events ++;
+ if (!mddev->in_sync || mddev->recovery_cp != MaxSector) { /* not clean */
+ /* .. if the array isn't clean, insist on an odd 'events' */
+ if ((mddev->events&1)==0) {
+ mddev->events++;
+ nospares = 0;
+ }
+ } else {
+ /* otherwise insist on an even 'events' (for clean states) */
+ if ((mddev->events&1)) {
+ mddev->events++;
+ nospares = 0;
+ }
+ }
+ }
if (!mddev->events) {
/*
@@ -1593,7 +1638,7 @@
mddev->events --;
}
mddev->sb_dirty = 2;
- sync_sbs(mddev);
+ sync_sbs(mddev, nospares);
/*
* do not write anything to disk if using
@@ -1615,6 +1660,8 @@
ITERATE_RDEV(mddev,rdev,tmp) {
char b[BDEVNAME_SIZE];
dprintk(KERN_INFO "md: ");
+ if (rdev->sb_loaded != 1)
+ continue; /* no noise on spare devices */
if (test_bit(Faulty, &rdev->flags))
dprintk("(skipping faulty ");
@@ -1626,6 +1673,7 @@
dprintk(KERN_INFO "(write) %s's sb offset: %llu\n",
bdevname(rdev->bdev,b),
(unsigned long long)rdev->sb_offset);
+ rdev->sb_events = mddev->events;
} else
dprintk(")\n");
@@ -1895,6 +1943,7 @@
rdev->desc_nr = -1;
rdev->flags = 0;
rdev->data_offset = 0;
+ rdev->sb_events = 0;
atomic_set(&rdev->nr_pending, 0);
atomic_set(&rdev->read_errors, 0);
atomic_set(&rdev->corrected_errors, 0);
@@ -4708,7 +4757,7 @@
spin_lock_irq(&mddev->write_lock);
if (mddev->in_sync) {
mddev->in_sync = 0;
- mddev->sb_dirty = 1;
+ mddev->sb_dirty = 3;
md_wakeup_thread(mddev->thread);
}
spin_unlock_irq(&mddev->write_lock);
@@ -5055,7 +5104,7 @@
if (mddev->safemode && !atomic_read(&mddev->writes_pending) &&
!mddev->in_sync && mddev->recovery_cp == MaxSector) {
mddev->in_sync = 1;
- mddev->sb_dirty = 1;
+ mddev->sb_dirty = 3;
}
if (mddev->safemode == 1)
mddev->safemode = 0;