The patch titled
md: improve setting of "events_cleared" for write-intent bitmaps.
has been added to the -mm tree. Its filename is
md-improve-setting-of-events_cleared-for-write-intent-bitmaps.patch
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------------------------------------------------------
Subject: md: improve setting of "events_cleared" for write-intent bitmaps.
From: NeilBrown <neilb@xxxxxxx>
When an array is degraded, bits in the write-intent bitmap are not
cleared, so that if the missing device is re-added, it can be synced by
only updated those parts of the device that have changed since it was
removed.
The enable this a 'events_cleared' value is stored. It is the event
counter for the array the last time that any bits were cleared.
Sometime - if a device disappears from an array while it is 'clean' - the
events_cleared value gets updated incorrectly (there are subtle ordering
issues between updateing events in the main metadata and the bitmap
metadata) resulting in the missing device appearing to require a full
resync when it is re-added.
With this patch, we update events_cleared precised when we are about to
clear a bit in the bitmap. This makes it more "obviously correct". We
also need to update events_cleared when the event_count is going backwards
(as happens on a dirty->clean transition of a non-degraded array).
Thanks to Mike Snitzer for identifying this problem and testing early
"fixes".
Cc: "Mike Snitzer" <snitzer@xxxxxxxxx>
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/md/bitmap.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff -puN drivers/md/bitmap.c~md-improve-setting-of-events_cleared-for-write-intent-bitmaps drivers/md/bitmap.c
--- a/drivers/md/bitmap.c~md-improve-setting-of-events_cleared-for-write-intent-bitmaps
+++ a/drivers/md/bitmap.c
@@ -454,8 +454,11 @@ void bitmap_update_sb(struct bitmap *bit
spin_unlock_irqrestore(&bitmap->lock, flags);
sb = (bitmap_super_t *)kmap_atomic(bitmap->sb_page, KM_USER0);
sb->events = cpu_to_le64(bitmap->mddev->events);
- if (!bitmap->mddev->degraded)
- sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
+ if (bitmap->mddev->events < bitmap->events_cleared) {
+ /* rocking back to read-only */
+ bitmap->events_cleared = bitmap->mddev->events;
+ sb->events_cleared = cpu_to_le64(bitmap->events_cleared);
+ }
kunmap_atomic(sb, KM_USER0);
write_page(bitmap, bitmap->sb_page, 1);
}
@@ -1085,9 +1088,22 @@ void bitmap_daemon_work(struct bitmap *b
} else
spin_unlock_irqrestore(&bitmap->lock, flags);
lastpage = page;
-/*
- printk("bitmap clean at page %lu\n", j);
-*/
+
+ /* We are possibly going to clear some bits, so make
+ * sure that events_cleared is up-to-date.
+ */
+ if (bitmap->events_cleared < bitmap->mddev->events) {
+ bitmap_super_t *sb;
+ bitmap->events_cleared = bitmap->mddev->events;
+ wait_event(bitmap->mddev->sb_wait,
+ !test_bit(MD_CHANGE_CLEAN,
+ &bitmap->mddev->flags));
+ sb = kmap_atomic(bitmap->sb_page, KM_USER0);
+ sb->events_cleared =
+ cpu_to_le64(bitmap->events_cleared);
+ kunmap_atomic(sb, KM_USER0);
+ write_page(bitmap, bitmap->sb_page, 1);
+ }
spin_lock_irqsave(&bitmap->lock, flags);
clear_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
}
_
Patches currently in -mm which might be from neilb@xxxxxxx are
origin.patch
linux-next.patch
md-fix-possible-oops-when-removing-a-bitmap-from-an-active-array.patch
md-proper-extern-for-mdp_major.patch
md-kill-file_path-wrapper.patch
md-md-raid5-rate-limit-error-printk.patch
md-raid1-fix-restoration-of-bio-between-failed-read-and-write.patch
md-notify-userspace-on-write-pending-changes-to-array_state.patch
md-notify-userspace-on-stop-events.patch
md-improve-setting-of-events_cleared-for-write-intent-bitmaps.patch
md-allow-parallel-resync-of-md-devices.patch
md-restart-recovery-cleanly-after-device-failure.patch
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