On Tue, Nov 23, 2010 at 12:07:36AM -0800, Kent Overstreet wrote: > On 11/21/2010 05:09 PM, Greg KH wrote: > >On Sun, Nov 21, 2010 at 06:09:34AM -0800, Kent Overstreet wrote: > >>+++ b/Documentation/bcache.txt > > > >For new sysfs files, please create Documentation/ABI files. > > > >>+All configuration is done via sysfs. To use sde to cache md1, assuming the > >>+SSD's erase block size is 128k: > >>+ > >>+ make-bcache -b128k /dev/sde > >>+ echo "/dev/sde"> /sys/kernel/bcache/register_cache > >>+ echo "<UUID> /dev/md1"> /sys/kernel/bcache/register_dev > > > >/sys/kernel/bcache/? Really? > > That was a completely arbitrary choice dating from when I first > started hacking on it. No point in moving it when it might be moved > again :p Heh. > >Come on, shouldn't this be somewhere else? You only have 1 file here, > >right? > > Two files (really three, but the third is for gimpy latency tracing > and will die eventually). register_dev is there so on bootup you > don't have to wait for the cache to be discovered - when you add a > cache device if there's a backing device waiting for a cache, and > the cache has seen that UUID before it'll do what you want. > > >Shouldn't it be a configfs file instead as that is what you are doing? > > That was one of the possibilities I had in mind. My main issue with > that though is I don't see any way to just have a bare config_item - > per the documentation, the user must do a mkdir() first, which just > doesn't make any sense for bcache. There's no point in having a > persistent object besides the one associated with the block device. > Maybe there would be in the future, with multiple cache devices, but > I still think it's a lousy interface for that problem - what bcache > wants is something more like a syscall; you wouldn't use configfs to > replace mount(), for example. True, but I thought configfs could handle "bare" config items, you might want to look a bit closer as to how people are using it. But I could be totally wrong however. > There do exist global interfaces in sysfs, not attached to any > device - besides /sys/kernel, there's /sys/fs which doesn't have any > rhyme or reason to it I can discern. /sys/fs is for different filesystem specific things. > ecryptfs has > /sys/ext4/ecryptfs/version, ext4 has per device stuff that you can't > find from the device's dir (you woludn't know /sys/fs/ext4/md0 > exists from looking at /sys/block/md0). There's also /sys/fs/cgroup, > which is another unique thing as far as I can tell... No, sys/fs/cgroup/ is where the cgroup filesystem is mounted. > Then there's /sys/module which has a bunch of ad hoc stuff, but as > far as I can tell that's all still module parameters and > register_cache and register_dev certainly aren't module parameters. It's not ad hoc, it's module specific things. > So anyways, I absolutely agree that there are better solutions than > /sys/kernel/bcache but I want to replace it with something correct, > not something that sucks less. Ideas/flames are of course more than > welcome :) What is "bcache"? Is it related to filesystems? If so, use /sys/fs/bcache and I have no issues with it. But don't put it in /sys/kernel/ without at least asking. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
