On 11/12/20 2:05 PM, JeffleXu wrote:
dm-table.c:dm_table_set_restrictions() has:
if (dm_table_supports_nowait(t))
blk_queue_flag_set(QUEUE_FLAG_NOWAIT, q);
else
blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, q);
This patch adds support for DM_TARGET_NOWAIT for those dm targets, the
.map() algorithm of which just involves sector recalculation.
So you're looking to constrain which targets will properly support
REQ_NOWAIT, based on whether they do a simple remapping?
To be honest, I'm a little confused about the semantics of REQ_NOWAIT.
Jens may had ever
explained it in block or io_uring mailing list, but I can't find the
specific mail.
I find it here
https://lore.kernel.org/linux-block/f1a6ae88-1436-e947-1124-41e10b3ea9bc@xxxxxxxxx/
So if the IO is offloaded to workqueue and the current process context
will not get blocked,
then is this device capable of handling REQ_NOWAIT or not?
--
Thanks,
Jeffle
