On Wed, Dec 20, 2017 at 04:47:21PM +0100, Christian Borntraeger wrote: > On 12/18/2017 02:56 PM, Stefan Haberland wrote: > > On 07.12.2017 00:29, Christoph Hellwig wrote: > >> On Wed, Dec 06, 2017 at 01:25:11PM +0100, Christian Borntraeger wrote: > >> t > commit 11b2025c3326f7096ceb588c3117c7883850c068 -> bad > >>> blk-mq: create a blk_mq_ctx for each possible CPU > >>> does not boot on DASD and > >>> commit 9c6ae239e01ae9a9f8657f05c55c4372e9fc8bcc -> good > >>> genirq/affinity: assign vectors to all possible CPUs > >>> does boot with DASD disks. > >>> > >>> Also adding Stefan Haberland if he has an idea why this fails on DASD and adding Martin (for the > >>> s390 irq handling code). > >> That is interesting as it really isn't related to interrupts at all, > >> it just ensures that possible CPUs are set in ->cpumask. > >> > >> I guess we'd really want: > >> > >> e005655c389e3d25bf3e43f71611ec12f3012de0 > >> "blk-mq: only select online CPUs in blk_mq_hctx_next_cpu" > >> > >> before this commit, but it seems like the whole stack didn't work for > >> your either. > >> > >> I wonder if there is some weird thing about nr_cpu_ids in s390? > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-s390" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> > > > > I tried this on my system and the blk-mq-hotplug-fix branch does not boot for me as well. > > The disks get up and running and I/O works fine. At least the partition detection and EXT4-fs mount works. > > > > But at some point in time the disk do not get any requests. > > > > I currently have no clue why. > > I took a dump and had a look at the disk states and they are fine. No error in the logs or in our debug entrys. Just empty DASD devices waiting to be called for I/O requests. > > > > Do you have anything I could have a look at? > > Jens, Christoph, so what do we do about this? > To summarize: > - commit 4b855ad37194f7 ("blk-mq: Create hctx for each present CPU") broke CPU hotplug. > - Jens' quick revert did fix the issue and did not broke DASD support but has some issues > with interrupt affinity. > - Christoph patch set fixes the hotplug issue for virtio blk but causes I/O hangs on DASDs (even > without hotplug). Hello, This one is a valid use case for VM, I think we need to fix that. Looks there is issue on the fouth patch("blk-mq: only select online CPUs in blk_mq_hctx_next_cpu"), I fixed it in the following tree, and the other 3 patches are same with Christoph's: https://github.com/ming1/linux.git v4.15-rc-block-for-next-cpuhot-fix gitweb: https://github.com/ming1/linux/commits/v4.15-rc-block-for-next-cpuhot-fix Could you test it and provide the feedback? BTW, if it can't help this issue, could you boot from a normal disk first and dump blk-mq debugfs of DASD later? Thanks, Ming
