Hi Ted, On Tue, Aug 20, 2019 at 12:25:10PM -0400, Theodore Y. Ts'o wrote: > On Tue, Aug 20, 2019 at 01:12:36PM +0800, Gao Xiang wrote: > > Add a word, I have some little concern about post read procession order > > a bit as I mentioned before, because I'd like to move common EROFS > > decompression code out in the future as well for other fses to use > > after we think it's mature enough. > > > > It seems the current code mainly addresses eliminating duplicated code, > > therefore I have no idea about that... > > Actually, we should chat. I was actually thinking about "borrowing" > code from erofs to provide ext4-specific compression. I was really > impressed with the efficiency goals in the erofs design[1] when I > reviewed the Usenix ATC paper, and as the saying goes, the best > artists know how to steal from the best. :-) > > [1] https://www.usenix.org/conference/atc19/presentation/gao I also guessed it's you reviewed our work as well from some written words :) (even though it's analymous...) and I personally think there are some useful stuffs in our EROFS effort. > > My original specific thinking was to do code reuse by copy and paste, > simply because it was simpler, and I have limited time to work on it. > But if you are interested in making the erofs pipeline reusable by > other file systems, and have the time to do the necessary code > refactoring, I'd love to work with you on that. Yes, I have interest in making the erofs pipeline for generic fses. Now I'm still investigating sequential read on very high speed NVME (like SAMSUNG 970pro, one thread seq read >3GB/s), it seems it still has some optimization space. And then I will do that work for generic fses as well... (but the first thing I want to do is getting erofs out of staging, as Greg said [1]) Metadata should be designed for each fs like ext4, but maybe not flexible and compacted as EROFS, therefore it could be some extra metadata overhead than EROFS. [1] https://lore.kernel.org/lkml/20190618064523.GA6015@xxxxxxxxx/ > > It should be noted that the f2fs developers have been working on their > own compression scheme that was going to be f2fs-specific, unlike the > file system generic approach used with fsverity and fscrypt. > > My expectation is that we will need to modify the read pipeling code > to support compression. That's true whether we are looking at the > existing file system-specific code used by ext4 and f2fs or in some > combined work such as what Chandan has proposed. I think either form is fine with me. :) But it seems that is some minor which tree we will work on (Maybe Chandan's work will be merged then). The first thing I need to do is to tidy up the code, and making it more general, and then it will be very easy for fses to integrate :) Thanks, Gao Xiang > > Cheers, > > - Ted
