On Wed, Aug 12, 2020 at 07:44:18AM +0800, Ming Lei wrote:
> When queue_max_discard_segments(q) is 1, blk_discard_mergable() will
> return false for discard request, then normal request merge is applied.
> However, only queue_max_segments() is checked, so max discard segment
> limit isn't respected.
>
> Check max discard segment limit in the request merge code for fixing
> the issue.
>
> Discard request failure of virtio_blk is fixed.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> Fixes: 69840466086d ("block: fix the DISCARD request merge")
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> block/blk-merge.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 5196dc145270..d18fb88ca8bd 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -533,10 +533,16 @@ int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
> }
> EXPORT_SYMBOL(__blk_rq_map_sg);
>
> +static inline unsigned int blk_rq_get_max_segments(struct request *rq)
> +{
> + return req_op(rq) == REQ_OP_DISCARD ?
> + queue_max_discard_segments(rq->q) : queue_max_segments(rq->q);
I'd go for a good old if statement here..
Otherwise looks good:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
