This is a note to let you know that I've just added the patch titled
md/raid5: limit request size according to implementation limits
to the 4.4-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-raid5-limit-request-size-according-to-implementation-limits.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e8d7c33232e5fdfa761c3416539bc5b4acd12db5 Mon Sep 17 00:00:00 2001
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Date: Sun, 27 Nov 2016 19:32:32 +0300
Subject: md/raid5: limit request size according to implementation limits
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
commit e8d7c33232e5fdfa761c3416539bc5b4acd12db5 upstream.
Current implementation employ 16bit counter of active stripes in lower
bits of bio->bi_phys_segments. If request is big enough to overflow
this counter bio will be completed and freed too early.
Fortunately this not happens in default configuration because several
other limits prevent that: stripe_cache_size * nr_disks effectively
limits count of active stripes. And small max_sectors_kb at lower
disks prevent that during normal read/write operations.
Overflow easily happens in discard if it's enabled by module parameter
"devices_handle_discard_safely" and stripe_cache_size is set big enough.
This patch limits requests size with 256Mb - 8Kb to prevent overflows.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/raid5.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6980,6 +6980,15 @@ static int run(struct mddev *mddev)
stripe = (stripe | (stripe-1)) + 1;
mddev->queue->limits.discard_alignment = stripe;
mddev->queue->limits.discard_granularity = stripe;
+
+ /*
+ * We use 16-bit counter of active stripes in bi_phys_segments
+ * (minus one for over-loaded initialization)
+ */
+ blk_queue_max_hw_sectors(mddev->queue, 0xfffe * STRIPE_SECTORS);
+ blk_queue_max_discard_sectors(mddev->queue,
+ 0xfffe * STRIPE_SECTORS);
+
/*
* unaligned part of discard request will be ignored, so can't
* guarantee discard_zeroes_data
Patches currently in stable-queue which might be from khlebnikov@xxxxxxxxxxxxxx are
queue-4.4/md-raid5-limit-request-size-according-to-implementation-limits.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html