On Thu, Jan 24, 2019 at 7:18 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > > Can you please point me in the direction of how to implement proper > > aops? Or better yet, send me a demo patch? > > I figure we need to call vfs_iter_read/vfs_iter_write of real file > > with IOCB_DIRECT for page io? But I am very uncertain about locking > > order requirements and whether there is already some infrastructure > > that we can use (some splice variant)? > > > > Any other thoughts? > > > > Miklos, > > I've made a small progress. > > Pushed two more commits to ovl-lazy-copyup-wip: > ea9a0083d1ed - ovl: readahead upper inode page cache on overlay page fault > d1ff6e6366d5 - ovl: implement overlay stacked readpage Pushed two more: 838c119934a2 - ovl: implement write_begin/write_end aops 44b9e89154ba - ovl: return overlay inode i_size for stat() > > That implements readpage by reading and copying from upper page cache. > > With that change, the basic unionmount test on tmpfs passes. That is not surprising. overlay filemap ops are disabled for upper tmpfs in current implementation, because tmpfs has no readpage(). > With unionmount over xfs, tests fail because partial page write > is not working correctly, although mmap partial write works well. > But that is fixed now, so ./run --ov --samefs also passes over xfs. Which says something bad about our test coverage... > I will try to follow similar pattern to implement writepage by copy to > upper page cache. > ...Luckily, I have implemented ./run --ov --recycle way back, otherwise we would have had very poor test coverage for persistency of overlayfs writes. So we currently have 6 xfstests failing on write persistency: overlay/018 overlay/032 overlay/044 overlay/047 overlay/050 overlay/051 and 2 unionmount tests (over /base xfs): ./run --ov --samefs --recycle rename-new-pop-dir ./run --ov --samefs --recycle rename-mass-dir Thanks, Amir.
