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]. [1] https://lore.kernel.org/lkml/13987.1539646128@xxxxxxxxxxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@xxxxxxxxx/ This patchset contains the following 2 patches: 0001-blkcg-fix-edge-case-for-blk_get_rl-under-memory-pres.patch 0002-blkcg-reassociate-bios-when-make_request-is-called-r.patch 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(-) Thanks, Dennis
