From mboxrd@z Thu Jan 1 00:00:00 1970 From: ming.lei@redhat.com (Ming Lei) Date: Thu, 9 May 2019 21:31:23 +0800 Subject: [PATCH] nvme-pci: fix single segment detection In-Reply-To: <20190509123406.GB21483@lst.de> References: <20190509110409.19647-1-hch@lst.de> <20190509112410.GA20711@ming.t460p> <20190509123406.GB21483@lst.de> Message-ID: <20190509133120.GA22059@ming.t460p> On Thu, May 09, 2019@02:34:06PM +0200, Christoph Hellwig wrote: > On Thu, May 09, 2019@07:24:12PM +0800, Ming Lei wrote: > > I'd suggest to fix block layer instead of working around the issue here, > > then any driver may benefit from the fix. > > That is my plan, and I started on it. But the fix isn't trivial, and > will probably take a while and be invasive. > > > Especially checking bio->bi_vcnt is just a hack, and drivers should > > never use .bi_vcnt. > > That is why it is explicitly commented as a hack. But a good enough > one to still speed up typical 4K I/Os - one a bio has been cloned > chances are very high we don't care about the fast path any more. NVMe hasn't max segment size limit, so fair enough for typical 4K IO workload: Reviewed-by: Ming Lei Thanks, Ming