On Tue, Oct 20, 2020 at 10:42 PM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > As you said, for the full page WRITE, we can probably mark it > page uptodate write away and drop page lock (Keep reference and > send WRITE request to fuse server). For the partial page write this will > not work and there seem to be atleast two options. > > A. Either we read the page back from disk first and mark it uptodate. > > B. Or we keep track of such partial writes and block any further > reads/readpage/direct_IO on these pages till partial write is > complete. After that looks like page will be left notuptodate > in page cache and reader will read it from disk. We are doing > something similar for tracking writeback requests. It is much > more complicated though and we probably can design something > simpler for these writethrough/synchronous writes. > > I am assuming that A. will lead to performance penalty for short > random writes. C. Keep partial tail page locked. If write involves a partial and head AND tail page, then read head page first. I think that would be a good compromise between performance and simplicity. WDYT? Thanks, Miklos
