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Groups > linux.kernel > #1208629 > unrolled thread

[PATCH] writeback: account BDI's min_ratio for unregistered device

Started byAkinobu Mita <akinobu.mita@gmail.com>
First post2015-08-17 16:50 +0200
Last post2015-08-17 22:00 +0200
Articles 2 — 2 participants

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  [PATCH] writeback: account BDI's min_ratio for unregistered device Akinobu Mita <akinobu.mita@gmail.com> - 2015-08-17 16:50 +0200
    Re: [PATCH] writeback: account BDI's min_ratio for unregistered  device Tejun Heo <tj@kernel.org> - 2015-08-17 22:00 +0200

#1208629 — [PATCH] writeback: account BDI's min_ratio for unregistered device

FromAkinobu Mita <akinobu.mita@gmail.com>
Date2015-08-17 16:50 +0200
Subject[PATCH] writeback: account BDI's min_ratio for unregistered device
Message-ID<pYtTA-1QB-17@gated-at.bofh.it>
From mm/page-writeback.c:

	/*
	 * bdi_min_ratio keeps the sum of the minimum dirty shares of all
	 * registered backing devices, which, for obvious reasons, can not
	 * exceed 100%.
	 */
	static unsigned int bdi_min_ratio;

But when a backing device is unregistered, the BDI's min_ratio is not
subtracted from bdi_min_ratio.  So the second attempt to set min_ratio
in the following commands will fail.

	# modprobe null_blk
	# echo 50 > /sys/block/nullb0/bdi/min_ratio
	# modprobe -r null_blk
	# modprobe null_blk
	# echo 50 > /sys/block/nullb0/bdi/min_ratio

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
---
 mm/backing-dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 42e0a63..92eefe3 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -849,6 +849,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
 	}
 
 	wb_exit(&bdi->wb);
+	bdi_set_min_ratio(bdi, 0);
 }
 EXPORT_SYMBOL(bdi_destroy);
 
-- 
1.9.1

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#1208846 — Re: [PATCH] writeback: account BDI's min_ratio for unregistered device

FromTejun Heo <tj@kernel.org>
Date2015-08-17 22:00 +0200
SubjectRe: [PATCH] writeback: account BDI's min_ratio for unregistered device
Message-ID<pYyJz-lu-5@gated-at.bofh.it>
In reply to#1208629
On Mon, Aug 17, 2015 at 11:45:53PM +0900, Akinobu Mita wrote:
> From mm/page-writeback.c:
> 
> 	/*
> 	 * bdi_min_ratio keeps the sum of the minimum dirty shares of all
> 	 * registered backing devices, which, for obvious reasons, can not
> 	 * exceed 100%.
> 	 */
> 	static unsigned int bdi_min_ratio;
> 
> But when a backing device is unregistered, the BDI's min_ratio is not
> subtracted from bdi_min_ratio.  So the second attempt to set min_ratio
> in the following commands will fail.
> 
> 	# modprobe null_blk
> 	# echo 50 > /sys/block/nullb0/bdi/min_ratio
> 	# modprobe -r null_blk
> 	# modprobe null_blk
> 	# echo 50 > /sys/block/nullb0/bdi/min_ratio
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Jens Axboe <axboe@kernel.dk>

Acked-by: Tejun Heo <tj@kernel.org>

We probably want to cc stable too.

Thanks.

-- 
tejun
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