DM currently uses atomic inc/dec to maintain a busy count of IO on a given device. For the dm-mq path, we can replace this with helper that just checks the state of the tags on the device.
First patch is a prep patch that allows the iteration helpers to return true/false, like we support internally in sbitmap. For a busy check we don't care about how many requests are busy, just if some are or not. Hence we can stop iterating tags as soon as we find one that is allocated. Changes since v1: - Remember to check if the queue matches, otherwise we could be returning false positive for shared tag sets. block/blk-mq-debugfs.c | 4 +++- block/blk-mq-tag.c | 4 ++-- block/blk-mq.c | 42 +++++++++++++++++++++++++++++++++++++----- include/linux/blk-mq.h | 6 ++++-- 4 files changed, 46 insertions(+), 10 deletions(-) -- Jens Axboe
