4.16-stable review patch. If anyone has any objections, please let me know.
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From: Ming Lei ming.lei@redhat.com
commit bffa9909a6b48d8ca3398dec601bc9162a4020c4 upstream.
From commit 4b855ad37194 ("blk-mq: Create hctx for each present CPU),
blk-mq doesn't remap queue after CPU topo is changed, that said when some of these offline CPUs become online, they are still mapped to hctx 0, then hctx 0 may become the bottleneck of IO dispatch and completion.
This patch sets up the mapping from the beginning, and aligns to queue mapping for PCI device (blk_mq_pci_map_queues()).
Cc: Stefan Haberland sth@linux.vnet.ibm.com Cc: Keith Busch keith.busch@intel.com Cc: stable@vger.kernel.org Fixes: 4b855ad37194 ("blk-mq: Create hctx for each present CPU) Tested-by: Christian Borntraeger borntraeger@de.ibm.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Sagi Grimberg sagi@grimberg.me Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- block/blk-mq-cpumap.c | 5 ----- 1 file changed, 5 deletions(-)
--- a/block/blk-mq-cpumap.c +++ b/block/blk-mq-cpumap.c @@ -16,11 +16,6 @@
static int cpu_to_queue_index(unsigned int nr_queues, const int cpu) { - /* - * Non present CPU will be mapped to queue index 0. - */ - if (!cpu_present(cpu)) - return 0; return cpu % nr_queues; }