On 09/23/2015 03:07 PM, Tejun Heo wrote:
inode_cgwb_enabled() gates cgroup writeback support. If it returns true, each inode is attached to the corresponding memory domain which gets mapped to io domain. It currently only tests whether the filesystem and bdi support cgroup writeback; however, cgroup writeback support doesn't work on traditional hierarchies and thus it should also test whether memcg and iocg are on the default hierarchy. This caused traditional hierarchy setups to hit the cgroup writeback path inadvertently and ended up creating separate writeback domains for each memcg and mapping them all to the root iocg uncovering a couple issues in the cgroup writeback path. cgroup writeback was never meant to be enabled on traditional hierarchies. Make inode_cgwb_enabled() test whether both memcg and iocg are on the default hierarchy. Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Reported-by: Artem Bityutskiy <dedekind1@xxxxxxxxx> Reported-by: Dexuan Cui <decui@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/g/1443012552.19983.209.camel@xxxxxxxxx Link: http://lkml.kernel.org/g/f30d4a6aa8a546ff88f73021d026a453@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx --- Hello, So, this should make the regression go away. It doesn't fix the underlying bugs but they shouldn't get triggered by people not experimenting with cgroup. I'm gonna keep digging the underlying issues but this should make the regressions go away. If it's okay, I think it'd be better to route this through cgroup/for-4.3-fixes as it's gonna cause a conflict with for-4.4 branch and handling the merge there is easier. Thanks. include/linux/backing-dev.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I'll ack this since it works around both the corruption issue and the performance regression, so we can avoid having to revert parts of this. And I know you'll keep hunting and get the real issue fixed in the mean time.
Acked-by: Jens Axboe <axboe@xxxxxx> -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
