On Thu, Sep 26, 2019 at 01:16:55PM -0700, Linus Torvalds wrote: > On Thu, Sep 26, 2019 at 1:09 PM Thomas Hellström (VMware) > <thomas_os@xxxxxxxxxxxx> wrote: > > > > That said, if people are OK with me modifying the assert in > > pud_trans_huge_lock() and make __walk_page_range non-static, it should > > probably be possible to make it work, yes. > > I don't think you need to modify that assert at all. > > That thing only exists when there's a "pud_entry" op in the walker, > and then you absolutely need to have that mmap_lock. > > As far as I can tell, you fundamentally only ever work on a pte level > in your address space walker already and actually have a WARN_ON() on > the pud_huge thing, so no pud entry can possibly apply. > > So no, the assert in pud_trans_huge_lock() does not seem to be a > reason not to just use the existing page table walkers. > > And once you get rid of the walking, what is left? Just the "iterate > over the inode mappings" part. Which could just be done in > mm/pagewalk.c, and then you don't even need to remove the static. > > So making it be just another walking in pagewalk.c would seem to be > the simplest model. > > Call it "walk_page_mapping()". And talk extensively about how the > locking differs a lot from the usual "walk_page_vma()" things. Walking mappings of a page is what rmap does. This code thas to be integrated there. -- Kirill A. Shutemov
