Revision - 111be88 - block-throttle: avoid double charge - origin: https://github.com/torvalds/linux

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05 April 2024, 19:05:47 UTC

Revision 111be883981748acc9a56e855c8336404a8e787c authored by Shaohua Li on 20 December 2017, 18:10:17 UTC, committed by Jens Axboe on 20 December 2017, 18:10:17 UTC

block-throttle: avoid double charge

If a bio is throttled and split after throttling, the bio could be
resubmited and enters the throttling again. This will cause part of the
bio to be charged multiple times. If the cgroup has an IO limit, the
double charge will significantly harm the performance. The bio split
becomes quite common after arbitrary bio size change.

To fix this, we always set the BIO_THROTTLED flag if a bio is throttled.
If the bio is cloned/split, we copy the flag to new bio too to avoid a
double charge. However, cloned bio could be directed to a new disk,
keeping the flag be a problem. The observation is we always set new disk
for the bio in this case, so we can clear the flag in bio_set_dev().

This issue exists for a long time, arbitrary bio size change just makes
it worse, so this should go into stable at least since v4.2.

V1-> V2: Not add extra field in bio based on discussion with Tejun

Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 parent 0abc2a1

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Tip revision: 111be883981748acc9a56e855c8336404a8e787c authored by Shaohua Li on 20 December 2017, 18:10:17 UTC
block-throttle: avoid double charge

Tip revision: 111be88

File	Mode	Size
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drivers
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fs
include
init
ipc
kernel
lib
mm
net
samples
scripts
security
sound
tools
usr
virt
.cocciconfig	-rw-r--r--	59 bytes
.get_maintainer.ignore	-rw-r--r--	31 bytes
.gitattributes	-rw-r--r--	30 bytes
.gitignore	-rw-r--r--	1.4 KB
.mailmap	-rw-r--r--	8.8 KB
COPYING	-rw-r--r--	18.3 KB
CREDITS	-rw-r--r--	96.2 KB
Kbuild	-rw-r--r--	2.2 KB
Kconfig	-rw-r--r--	287 bytes
MAINTAINERS	-rw-r--r--	425.8 KB
Makefile	-rw-r--r--	58.3 KB
README	-rw-r--r--	722 bytes

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block-throttle: avoid double charge

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