Commit e8d7c332 authored Nov 27, 2016 by Konstantin Khlebnikov Committed by Shaohua Li Nov 29, 2016

md/raid5: limit request size according to implementation limits



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@yandex-team.ru>
Cc: Shaohua Li <shli@kernel.org>
Cc: Neil Brown <neilb@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: Shaohua Li <shli@fb.com>

parent 1a0ec5c3

drivers/md/raid5.c

+9 −0

Original line number	Original line	Diff line number	Diff line
	@@ -7108,6 +7108,15 @@ static int raid5_run(struct mddev *mddev)
	stripe = (stripe \| (stripe-1)) + 1;		stripe = (stripe \| (stripe-1)) + 1;
	mddev->queue->limits.discard_alignment = stripe;		mddev->queue->limits.discard_alignment = stripe;
	mddev->queue->limits.discard_granularity = 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		* unaligned part of discard request will be ignored, so can't
	* guarantee discard_zeroes_data		* guarantee discard_zeroes_data

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