On Wednesday, 31 March 2021 2:56:38 PM AEDT John Hubbard wrote:
On 3/30/21 3:56 PM, Alistair Popple wrote: ...
+1 for renaming "munlock*" items to "mlock*", where applicable. good
grief.
At least the situation was weird enough to prompt further investigation :)
Renaming to mlock* doesn't feel like the right solution to me either
though. I
am not sure if you saw me responding to myself earlier but I am thinking renaming try_to_munlock() -> page_mlocked() and try_to_munlock_one() -> page_mlock_one() might be better. Thoughts?
Quite confused by this naming idea. Because: try_to_munlock() returns void, so a boolean-style name such as "page_mlocked()" is already not a good fit.
Even more important, though, is that try_to_munlock() is mlock-ing the page, right? Is there some subtle point I'm missing? It really is doing an mlock to the best of my knowledge here. Although the kerneldoc comment for try_to_munlock() seems questionable too:
It's mlocking the page if it turns out it still needs to be locked after unlocking it. But I don't think you're missing anything.
/**
- try_to_munlock - try to munlock a page
- @page: the page to be munlocked
- Called from munlock code. Checks all of the VMAs mapping the page
- to make sure nobody else has this page mlocked. The page will be
- returned with PG_mlocked cleared if no other vmas have it mlocked.
*/
...because I don't see where, in *this* routine, it clears PG_mlocked!
Obviously we agree that a routine should be named based on what it does, rather than on who calls it. So I think that still leads to:
try_to_munlock() --> try_to_mlock() try_to_munlock_one() --> try_to_mlock_one()Sorry if I'm missing something really obvious.
Nope, I confused things somewhat by blindly quoting the documentation whilst forgetting that try_to_munlock() returns void rather than a bool.
This is actually inspired from a suggestion in Documentation/vm/
unevictable-
lru.rst which warns about this problem:
try_to_munlock() Reverse Map Scan
.. warning:: [!] TODO/FIXME: a better name might be page_mlocked() - analogous to
the
page_referenced() reverse map walker.This is actually rather bad advice! page_referenced() returns an int-that-is-really-a-boolean, whereas try_to_munlock(), at least as it stands now, returns void. Usually when I'm writing a TODO item, I'm in a hurry, and I think that's what probably happened here, too. :)
So I think we're in agreement. The naming is bad and the advice in the documentation is also questionable :-)
Thanks for the thoughts, I will re-send this with naming and documentation updates.
Although, it seems reasonable to tack such renaming patches onto the tail
end
of this series. But whatever works.
Unless anyone objects strongly I will roll the rename into this patch as
there
is only one caller of try_to_munlock.
- Alistair
No objections here. :)
thanks,