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charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 12.04.2021 09:44, Christoph Hellwig wrote: >On Fri, Apr 09, 2021 at 08:24:01PM +0900, Minwoo Im wrote: >> I think if we don't have a route to the live controller from the >> multipath node /dev/ng0n1, how does application figure out controller >> node to request admin commands like Identify Namespace before their >> own I/O ? >> >> We have sysfs, but it does not provide every information about the >> namespace. Or is there any charming way to find out the live >> controller from a head node through sysfs or something that I missed >> here ? :) > >The devie links points to the subsystem, which then points to the >controllers: > >root@testvm:/sys/class/nvme-generic/ng0n1# ls -l device/ >total 0 >-r--r--r-- 1 root root 4096 Apr 12 07:43 firmware_rev >-rw-r--r-- 1 root root 4096 Apr 12 07:44 iopolicy >-r--r--r-- 1 root root 4096 Apr 12 07:43 model >drwxr-xr-x 3 root root 0 Apr 12 07:43 ng0n1 >drwxr-xr-x 3 root root 0 Apr 12 07:43 ng0n2 >lrwxrwxrwx 1 root root 0 Apr 12 07:44 nvme0 -> ../../nvme-fabrics/ctl/nvme0 >drwxr-xr-x 9 root root 0 Apr 12 07:43 nvme0n1 >drwxr-xr-x 9 root root 0 Apr 12 07:43 nvme0n2 >lrwxrwxrwx 1 root root 0 Apr 12 07:44 nvme1 -> ../../nvme-fabrics/ctl/nvme1 >drwxr-xr-x 2 root root 0 Apr 12 07:44 power >-r--r--r-- 1 root root 4096 Apr 12 07:43 serial >-r--r--r-- 1 root root 4096 Apr 12 07:44 subsysnqn >lrwxrwxrwx 1 root root 0 Apr 12 07:43 subsystem -> ../../../../class/nvme-subsystem >-rw-r--r-- 1 root root 4096 Apr 12 07:43 uevent > It seems like a limitation that we have to transverse sysfs to make an in-application enumeration to submit namespace-specific admin commands. Ideally, applications that are already using IOCTLs should be able to directly work with the char device. If this is not the case, I am afraid that the applicability will be limited. I understand that identifying the live controller in multipath is something that we need to improve. The question is that if this is a reasonable thing for you. If there is no fundamental limitation here, I think we can work the details of enabling namespace admin commands through and merge the same support for the block device and the char device. What do you think? _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme