On 14/02/2019 20:25, Dan Williams wrote: > On Thu, Feb 14, 2019 at 5:46 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote: >> >> On Wed 06-02-19 13:12:59, Dan Williams wrote: >> [...] >>> * Userfaultfd for file-backed mappings and DAX >> >> I assume that other topics are meant to be FS track but this one is MM, >> right? > > Yes, but I think it is the lowest priority of all the noted sub-topics > in this proposal. The DAX-reflink discussion, where a given > physical-page may need to be mapped into multiple inodes at different > offsets, might be more fruitful to have as a joint discussion with MM. > This topic is very interesting to me. In current ZUFS implementation we support this option for a long time. IE: Map same pte_t into different indexes of the same file-mappings as well as in vma(s) of different files, at different indexes. Including invalidation of mapping of a pwrite into such a shared page. (A write to a shared block will allocate a new block for writing) This effort off-course involves the participation of the FileSystem to give a list of files and indexes for map_unmapping(). I can explain if you want how we did this. Cheers Boaz
