On Tue, Sep 25, 2007 at 12:11:23PM +0200, Kay Sievers wrote: > On Tue, 2007-09-25 at 11:14 +0200, Karel Zak wrote: > > Now we duplicate a lot of FS probe code in libblkid, libvolume_id and > > libdisk. > > > > Yes, it's long-term task, but it's good direction (IMHO). > > It is, and we are not providing a real value to the users by providing > both of these libs at the same time. :) > > But udev has a very different requirement for probing filesystems. > Unlike non-udev systems, we can't accept any hidden policy inside a > library. We just want to pass a byte stream to the lib, and get back > what exactly is in _this_ byte stream. There must be no chaching, no > devmapper logic, no stat()'ing in /dev, no reading of /proc/partitions, > no ioctl()'s, no hidden decisions, nothing. None of these actions is > acceptable to be done by the library itself, if udev is used. We need > pure mechanics, no policy. We also need an API that allows to specify > the size of the stream and the probing offset. And we don't want to > iterate over tags, need the filesystem version information, the raid > metadata probing, and the classification volume_id provides.
Technical details :-) > That means that we could replace the "low-level" part of libblkid with > volume_id code, and keep the current API of blkid, but offer some of the > low-level functionality for udev. Or we would implement the relevant > parts and probers in blkid, and add a new API to access the low-level > part directly. I don't see a problem to provide low-level and high-level interface in same library. The low-level stuff (fsprobe code) is still same. Things like a cache are discussable -- for example resolve LABEL/UUID on system with udev is faster by /dev/disk/by-*. I think a good library has to be smart enough to found the fastest way how translate LABEL/UUID to device name. But, it's too early to talk about details. > Let me know what you think how go ahead with this, I'm all for doing > this sooner than later. Cool. I'd like to create libfsprobe as an independent project. Or is there any advantage to merge everything to util-linux-ng? I don't think so. Karel -- Karel Zak <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html