Messages in this thread | | | Subject | Re: Ack to merge through DRM? WAS Re: [PATCH v2 1/5] mm: Add write-protect and clean utilities for address space ranges | From | Thomas Hellström (VMware) <> | Date | Wed, 2 Oct 2019 11:21:01 +0200 |
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On 9/26/19 10:16 PM, Linus Torvalds wrote: > On Thu, Sep 26, 2019 at 1:09 PM Thomas Hellström (VMware) > <thomas_os@shipmail.org> 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.
Thanks,
Thomas
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