This is a note to let you know that I've just added the patch titled
md: flush writes before starting a recovery.
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
md-flush-writes-before-starting-a-recovery.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 133d4527eab8d199a62eee6bd433f0776842df2e Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 2 Jul 2014 12:04:14 +1000
Subject: md: flush writes before starting a recovery.
From: NeilBrown <neilb@xxxxxxx>
commit 133d4527eab8d199a62eee6bd433f0776842df2e upstream.
When we write to a degraded array which has a bitmap, we
make sure the relevant bit in the bitmap remains set when
the write completes (so a 're-add' can quickly rebuilt a
temporarily-missing device).
If, immediately after such a write starts, we incorporate a spare,
commence recovery, and skip over the region where the write is
happening (because the 'needs recovery' flag isn't set yet),
then that write will not get to the new device.
Once the recovery finishes the new device will be trusted, but will
have incorrect data, leading to possible corruption.
We cannot set the 'needs recovery' flag when we start the write as we
do not know easily if the write will be "degraded" or not. That
depends on details of the particular raid level and particular write
request.
This patch fixes a corruption issue of long standing and so it
suitable for any -stable kernel. It applied correctly to 3.0 at
least and will minor editing to earlier kernels.
Reported-by: Bill <billstuff2001@xxxxxxxxxxxxx>
Tested-by: Bill <billstuff2001@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/53A518BB.60709@xxxxxxxxxxxxx
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/md.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7491,6 +7491,19 @@ void md_do_sync(struct md_thread *thread
rdev->recovery_offset < j)
j = rdev->recovery_offset;
rcu_read_unlock();
+
+ /* If there is a bitmap, we need to make sure all
+ * writes that started before we added a spare
+ * complete before we start doing a recovery.
+ * Otherwise the write might complete and (via
+ * bitmap_endwrite) set a bit in the bitmap after the
+ * recovery has checked that bit and skipped that
+ * region.
+ */
+ if (mddev->bitmap) {
+ mddev->pers->quiesce(mddev, 1);
+ mddev->pers->quiesce(mddev, 0);
+ }
}
printk(KERN_INFO "md: %s of RAID array %s\n", desc, mdname(mddev));
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-3.15/md-make-sure-get_array_info-ioctl-reports-correct-clean-status.patch
queue-3.15/md-flush-writes-before-starting-a-recovery.patch
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