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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 2/9] mm: pagewalk: Take the pagetable lock in walk_pte_range()
Date: Wed, 9 Oct 2019 09:07:00 -0700	[thread overview]
Message-ID: <CAHk-=wh=zsXPmSTJJgEgVr4ebgwTQ-wx-P1c7+koJAK-h2f_vQ@mail.gmail.com> (raw)
In-Reply-To: <20191009151400.bserdtpoczmawqn5@box>

On Wed, Oct 9, 2019 at 8:14 AM Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> If ->pte_entry() fails on the first entry of the page table, pte - 1 will
> point out side the page table.
>
> And the '- 1' is totally unnecessary as we break the loop before pte++ on
> the last iteration.

Good catch. Too much copying the wrong pattern from other sources.

I do wish we didn't have this pattern of "update pte, then do
pte_unmap as long as it's in the same page". Yeah, it avoids a
variable, but still... But it is what it is, and we just need to be
careful.

             Linus

  reply	other threads:[~2019-10-09 16:07 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 [this message]
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 16:20     ` Thomas Hellström (VMware)
2019-10-09 16:21     ` Linus Torvalds
2019-10-09 16:21       ` Linus Torvalds
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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