From d432c817c21a48c3baaa0d28e4d3e74b6aa238a0 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 10 Jan 2025 06:47:12 +0100 Subject: block: don't update BLK_FEAT_POLL in __blk_mq_update_nr_hw_queues When __blk_mq_update_nr_hw_queues changes the number of tag sets, it might have to disable poll queues. Currently it does so by adjusting the BLK_FEAT_POLL, which is a bit against the intent of features that describe hardware / driver capabilities, but more importantly causes nasty lock order problems with the broadly held freeze when updating the number of hardware queues and the limits lock. Fix this by leaving BLK_FEAT_POLL alone, and instead check for the number of poll queues in the bio submission and poll handlers. While this adds extra work to the fast path, the variables are in cache lines used by these operations anyway, so it should be cheap enough. Fixes: 8023e144f9d6 ("block: move the poll flag to queue_limits") Signed-off-by: Christoph Hellwig Reviewed-by: Ming Lei Reviewed-by: Damien Le Moal Reviewed-by: Martin K. Petersen Reviewed-by: Johannes Thumshirn Reviewed-by: Nilay Shroff Link: https://lore.kernel.org/r/20250110054726.1499538-5-hch@lst.de Signed-off-by: Jens Axboe --- block/blk-sysfs.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'block/blk-sysfs.c') diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 767598e719ab..e9f1c82b2f3e 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -245,10 +245,17 @@ static ssize_t queue_##_name##_show(struct gendisk *disk, char *page) \ !!(disk->queue->limits.features & _feature)); \ } -QUEUE_SYSFS_FEATURE_SHOW(poll, BLK_FEAT_POLL); QUEUE_SYSFS_FEATURE_SHOW(fua, BLK_FEAT_FUA); QUEUE_SYSFS_FEATURE_SHOW(dax, BLK_FEAT_DAX); +static ssize_t queue_poll_show(struct gendisk *disk, char *page) +{ + if (queue_is_mq(disk->queue)) + return sysfs_emit(page, "%u\n", blk_mq_can_poll(disk->queue)); + return sysfs_emit(page, "%u\n", + !!(disk->queue->limits.features & BLK_FEAT_POLL)); +} + static ssize_t queue_zoned_show(struct gendisk *disk, char *page) { if (blk_queue_is_zoned(disk->queue)) -- cgit v1.2.3