From: Alistair Popple <apopple@nvidia.com>
To: John Hubbard <jhubbard@nvidia.com>
Cc: rcampbell@nvidia.com, willy@infradead.org,
linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
kvm-ppc@vger.kernel.org, hch@infradead.org, linux-mm@kvack.org,
jglisse@redhat.com, bskeggs@redhat.com,
Jason Gunthorpe <jgg@nvidia.com>,
akpm@linux-foundation.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v7 3/8] mm/rmap: Split try_to_munlock from try_to_unmap
Date: Wed, 31 Mar 2021 09:56:20 +1100 [thread overview]
Message-ID: <12636584.zsJ0Sx4KLp@nvdebian> (raw)
In-Reply-To: <bce0605a-336f-99ba-5b65-a8e5a7e49e00@nvidia.com>
On Wednesday, 31 March 2021 9:43:19 AM AEDT John Hubbard wrote:
> On 3/30/21 3:24 PM, Jason Gunthorpe wrote:
> ...
> >> As far as I can tell this has always been called try_to_munlock() even
though
> >> it appears to do the opposite.
> >
> > Maybe we should change it then?
> >
> >>> /**
> >>> * 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.
> >>> */
> >>
> >> In other words it sets PG_mlocked if one or more vmas has it mlocked. So
> >> try_to_mlock() might be a better name, except that seems to have the
potential
> >> for confusion as well because it's only called from the munlock code path
and
> >> never for mlock.
> >
> > That explanation makes more sense.. This function looks like it is
> > 'set PG_mlocked of the page if any vm->flags has VM_LOCKED'
> >
> > Maybe call it check_vm_locked or something then and reword the above
> > comment?
> >
> > (and why is it OK to read vm->flags for this without any locking?)
> >
> >>> Something needs attention here..
> >>
> >> I think the code is correct, but perhaps the naming could be better.
Would be
> >> interested hearing any thoughts on renaming try_to_munlock() to
try_to_mlock()
> >> as the current name appears based on the context it is called from
(munlock)
> >> rather than what it does (mlock).
> >
> > The point of this patch is to make it clearer, after all, so I'd
> > change something and maybe slightly clarify the comment.
> >
Yep, agree with that.
> I'd add that, after looking around the calling code, this is a really
unhappy
> pre-existing situation. Anyone reading this has to remember at which point
in the
> call stack the naming transitions from "do the opposite of what the name
says",
> to "do what the name says".
>
> +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?
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.
> 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
> thanks,
>
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2021-03-30 22:56 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-26 0:07 [PATCH v7 0/8] Add support for SVM atomics in Nouveau Alistair Popple
2021-03-26 0:07 ` [PATCH v7 1/8] mm: Remove special swap entry functions Alistair Popple
2021-03-30 18:38 ` Jason Gunthorpe
2021-03-26 0:07 ` [PATCH v7 2/8] mm/swapops: Rework swap entry manipulation code Alistair Popple
2021-03-26 0:08 ` [PATCH v7 3/8] mm/rmap: Split try_to_munlock from try_to_unmap Alistair Popple
2021-03-30 18:49 ` Jason Gunthorpe
2021-03-30 22:09 ` Alistair Popple
2021-03-30 22:16 ` Alistair Popple
2021-03-30 22:24 ` Jason Gunthorpe
2021-03-30 22:43 ` John Hubbard
2021-03-30 22:56 ` Alistair Popple [this message]
2021-03-31 3:56 ` John Hubbard
2021-03-31 4:09 ` John Hubbard
2021-03-31 4:15 ` Alistair Popple
2021-03-31 11:57 ` Jason Gunthorpe
2021-04-01 4:36 ` Alistair Popple
2021-04-01 19:21 ` Shakeel Butt
2021-03-26 0:08 ` [PATCH v7 4/8] mm/rmap: Split migration into its own function Alistair Popple
2021-03-26 0:08 ` [PATCH v7 5/8] mm: Device exclusive memory access Alistair Popple
2021-03-30 19:32 ` Jason Gunthorpe
2021-03-31 12:59 ` Alistair Popple
2021-03-31 13:18 ` Jason Gunthorpe
2021-03-31 13:27 ` Alistair Popple
2021-03-31 13:46 ` Jason Gunthorpe
2021-04-01 0:45 ` Alistair Popple
2021-04-01 0:48 ` Jason Gunthorpe
2021-04-01 2:20 ` Alistair Popple
2021-04-01 11:55 ` Jason Gunthorpe
2021-03-26 0:08 ` [PATCH v7 6/8] mm: Selftests for exclusive device memory Alistair Popple
2021-03-26 0:08 ` [PATCH v7 7/8] nouveau/svm: Refactor nouveau_range_fault Alistair Popple
2021-03-26 0:08 ` [PATCH v7 8/8] nouveau/svm: Implement atomic SVM access Alistair Popple
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=12636584.zsJ0Sx4KLp@nvdebian \
--to=apopple@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=bskeggs@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@infradead.org \
--cc=hch@lst.de \
--cc=jgg@nvidia.com \
--cc=jglisse@redhat.com \
--cc=jhubbard@nvidia.com \
--cc=kvm-ppc@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=nouveau@lists.freedesktop.org \
--cc=rcampbell@nvidia.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).