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From: Dennis Zhou <>
To: Jens Axboe <>
Cc: Tejun Heo <>,
	Valdis Kletnieks <>,,,, Dennis Zhou <>
Subject: [PATCH 0/2] block: fixes for always associate blkg
Date: Sat, 20 Oct 2018 14:56:10 -0400
Message-ID: <> (raw)

Hi everyone,

It was reported in [1] that blk_get_rl() cleanup patch was causing a
null pointer dereference. After some back and forth debugging with
Valdis, it turns out I wasn't properly handling association with
recursive calls to make_request().

Another issue was identified with the blk_get_rl() update as it is
possible under certain circumstances that a blkg cannot be allocated
when called in blk_get_rl(). This could result in the blkcg_root being
returned. However, the blkcg_root is a special case where all blkgs
share the request_queue's request_list.

The original series can be found at [2].


This patchset contains the following 2 patches:

0001 addresses an edge case where a blkg cannot be created and can
possibly return a blkg associated with the blkcg_root. 0002 fixes the
stale association when make_request() is called recursively.

This patchset is on top of axboe#for-4.20/block bbc152825afc.

diffstats below:

Dennis Zhou (2):
  blkcg: fix edge case for blk_get_rl() under memory pressure
  blkcg: reassociate bios when make_request() is called recursively

 block/bio.c                | 20 ++++++++++++++++++++
 block/blk-core.c           |  1 +
 include/linux/bio.h        |  3 +++
 include/linux/blk-cgroup.h |  2 +-
 4 files changed, 25 insertions(+), 1 deletion(-)


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-20 18:56 Dennis Zhou [this message]
2018-10-20 18:56 ` [PATCH 1/2] blkcg: fix edge case for blk_get_rl() under memory pressure Dennis Zhou
2018-10-20 18:56 ` [PATCH 2/2] blkcg: reassociate bios when make_request() is called recursively Dennis Zhou
2018-10-20 21:40 ` [PATCH 0/2] block: fixes for always associate blkg Jens Axboe

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