From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
"Thomas Hellstrom" <thellstrom@vmware.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Will Deacon" <will.deacon@arm.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Rik van Riel" <riel@surriel.com>,
"Minchan Kim" <minchan@kernel.org>,
"Michal Hocko" <mhocko@suse.com>,
"Huang Ying" <ying.huang@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>
Subject: Re: [PATCH v4 3/9] mm: pagewalk: Don't split transhuge pmds when a pmd_entry is present
Date: Wed, 9 Oct 2019 09:21:08 -0700 [thread overview]
Message-ID: <CAHk-=wh4waroKr-Xtcv+5pTxBcHxGEj-g73eQvXVawML_C0EXw@mail.gmail.com> (raw)
In-Reply-To: <20191009152737.p42w7w456zklxz72@box>
On Wed, Oct 9, 2019 at 8:27 AM Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> Do we have any current user that expect split_huge_pmd() in this scenario.
No. There are no current users of the pmd callback and the pte
callback at all, that I could find.
But it looks like the new drm use does want a "I can't handle the
hugepage, please split it and I'll fo the ptes instead".
> That's hacky.
>
> Maybe just use an error code for this? -EAGAIN?
I actually like the PAGE_WALK_FALLBACK thing as more documentation
than "it's an error, but not one you return", although I do detest the
particular value chosen, which is just a nasty bitpattern.
Maybe it could use an error value, just one that makes no sense, and
is hidden by the PAGE_WALK_FALLBACK define, ie something like
#define PAGE_WALK_FALLBACK (-ECHILD)
or something like that.
And I suspect the conditional would be cleaner if it was written something like
if (!err)
continue;
if (err != PAGE_WALK_FALLBACK)
break;
err = 0;
if (pmd_trans_unstable(pmd))
goto again;
.. do the split ..
and skip the WARN_ON() and the odd "non-zero but smaller than MAX test"
Linus
next prev parent reply other threads:[~2019-10-09 16:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 9:14 [PATCH v4 0/9] Emulated coherent graphics memory take 2 Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 1/9] mm: Remove BUG_ON mmap_sem not held from xxx_trans_huge_lock() Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 2/9] mm: pagewalk: Take the pagetable lock in walk_pte_range() Thomas Hellström (VMware)
2019-10-09 15:14 ` Kirill A. Shutemov
2019-10-09 16:07 ` Linus Torvalds
2019-10-08 9:15 ` [PATCH v4 3/9] mm: pagewalk: Don't split transhuge pmds when a pmd_entry is present Thomas Hellström (VMware)
2019-10-09 15:27 ` Kirill A. Shutemov
2019-10-09 15:27 ` Kirill A. Shutemov
2019-10-09 16:20 ` Thomas Hellström (VMware)
2019-10-09 16:20 ` Thomas Hellström (VMware)
2019-10-09 16:21 ` Linus Torvalds [this message]
2019-10-09 17:03 ` Thomas Hellström (VMware)
2019-10-09 17:16 ` Linus Torvalds
2019-10-09 18:52 ` Thomas Hellstrom
2019-10-09 19:20 ` Linus Torvalds
2019-10-09 20:06 ` Thomas Hellström (VMware)
2019-10-09 20:20 ` Linus Torvalds
2019-10-09 22:30 ` Thomas Hellström (VMware)
2019-10-09 23:50 ` Thomas Hellström (VMware)
2019-10-09 23:51 ` Linus Torvalds
2019-10-10 0:18 ` Linus Torvalds
2019-10-10 1:09 ` Thomas Hellström (VMware)
2019-10-10 2:07 ` Linus Torvalds
2019-10-10 6:15 ` Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 4/9] mm: Add a walk_page_mapping() function to the pagewalk code Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 5/9] mm: Add write-protect and clean utilities for address space ranges Thomas Hellström (VMware)
2019-10-08 17:06 ` Linus Torvalds
2019-10-08 18:25 ` Thomas Hellstrom
2019-10-08 9:15 ` [PATCH v4 6/9] drm/vmwgfx: Implement an infrastructure for write-coherent resources Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 7/9] drm/vmwgfx: Use an RBtree instead of linked list for MOB resources Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 8/9] drm/vmwgfx: Implement an infrastructure for read-coherent resources Thomas Hellström (VMware)
2019-10-08 9:15 ` [PATCH v4 9/9] drm/vmwgfx: Add surface dirty-tracking callbacks Thomas Hellström (VMware)
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