On Wed, Oct 02, 2019 at 11:21:01AM +0200, Thomas Hellström (VMware) wrote: > On 9/26/19 10:16 PM, 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. > > > > The then actual "apply" functions (what a horrid name) could be in the > > users. They shouldn't be mixed in with the walking functions anyway. > > They are callbacks, not walkers. > > > > Linus > > Linus, Kirill > > I've pushed a reworked version based on the pagewalk code here: > > https://cgit.freedesktop.org/~thomash/linux/log/?h=pagewalk > > (top three patched) > > with users included here: > > https://cgit.freedesktop.org/~thomash/linux/log/?h=coherent-rebased > > Do you think this could work? The reason that the "mm: Add write-protect and > clean.." code is still in mm as a set of helpers, is of course that much of > the needed functionality is not exported, presumably since we want to keep > page table manipulation in mm. Could you post it to the mailing list? It's easier to review this way. -- Kirill A. Shutemov
