From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Fri, 26 Jul 2019 09:13:49 +0200 Subject: [PATCH v6 02/16] chardev: introduce cdev_get_by_path() In-Reply-To: <7f48a40c-6e0f-2545-a939-45fc10862dfd@grimberg.me> References: <682ff89f-04e0-7a94-5aeb-895ac65ee7c9@deltatee.com> <20190725180816.GA32305@kroah.com> <20190725182701.GA11547@kroah.com> <20190725190024.GD30641@bombadil.infradead.org> <27943e06-a503-162e-356b-abb9e106ab2e@grimberg.me> <20190725191124.GE30641@bombadil.infradead.org> <425dd2ac-333d-a8c4-ce49-870c8dadf436@deltatee.com> <20190725235502.GJ1131@ZenIV.linux.org.uk> <7f48a40c-6e0f-2545-a939-45fc10862dfd@grimberg.me> Message-ID: <20190726071349.GA16265@kroah.com> On Thu, Jul 25, 2019@09:29:40PM -0700, Sagi Grimberg wrote: > > > > > > > > > NVMe-OF is configured using configfs. The target is specified by the > > > > > > > > user writing a path to a configfs attribute. This is the way it works > > > > > > > > today but with blkdev_get_by_path()[1]. For the passthru code, we need > > > > > > > > to get a nvme_ctrl instead of a block_device, but the principal is the same. > > > > > > > > > > > > > > Why isn't a fd being passed in there instead of a random string? > > > > > > > > > > > > I suppose we could echo a string of the file descriptor number there, > > > > > > and look up the fd in the process' file descriptor table ... > > > > > > > > > > Assuming that there is a open handle somewhere out there... > > > > > > Yes, that would be a step backwards from an interface. The user would > > > then need a special process to open the fd and pass it through configfs. > > > They couldn't just do it with basic bash commands. > > > > First of all, they can, but... WTF not have filp_open() done right there? > > Yes, by name. With permission checks done. And pick your object from the > > sodding struct file you'll get. > > > > What's the problem? Why do you need cdev lookups, etc., when you are > > dealing with files under your full control? Just open them and use > > ->private_data or whatever you set in ->open() to access the damn thing. > > All there is to it... > Oh this is so much simpler. There is really no point in using anything > else. Just need to remember to compare f->f_op to what we expect to make > sure that it is indeed the same device class. That is good, that solves the "/dev/random/" issue I was talking about earlier as well. Odds are you all can do the same for the blockdev interface as well. thanks, greg k-h