On Tue, Sep 03, 2019 at 02:14:24PM +0200, Michal Hocko wrote: > On Mon 02-09-19 03:23:41, William Kucharski wrote: > > Add filemap_huge_fault() to attempt to satisfy page > > faults on memory-mapped read-only text pages using THP when possible. > > This deserves much more description of how the thing is implemented and > expected to work. For one thing it is not really clear to me why you > need CONFIG_RO_EXEC_FILEMAP_HUGE_FAULT_THP at all. You need a support > from the filesystem anyway. So who is going to enable/disable this > config? There are definitely situations in which enabling this code will crash the kernel. But we want to get filesystems to a point where they can start working on their support for large pages. So our workaround is to try to get the core pieces merged under a CONFIG_I_KNOW_WHAT_IM_DOING flag and let people play with it. Then continue to work on the core to eliminate those places that are broken. > I cannot really comment on fs specific parts but filemap_huge_fault > sounds convoluted so much I cannot wrap my head around it. One thing > stand out though. The generic filemap_huge_fault depends on ->readpage > doing the right thing which sounds quite questionable to me. If nothing > else I would expect ->readpages to do the job. Ah, that's because you're not a filesystem person ;-) ->readpages is really ->readahead. It's a crappy interface and should be completely redesigned. Thanks for looking!
