From: Punit Agrawal <punit.agrawal@arm.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Punit Agrawal <punit.agrawal@arm.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, steve.capper@arm.com,
will.deacon@arm.com, catalin.marinas@arm.com,
kirill.shutemov@linux.intel.com, Michal Hocko <mhocko@suse.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH 0/1] Clarify huge_pte_offset() semantics
Date: Tue, 25 Jul 2017 16:41:13 +0100 [thread overview]
Message-ID: <20170725154114.24131-1-punit.agrawal@arm.com> (raw)
Hi,
The following patch is an attempt to make huge_pte_offset() consistent
when dealing with different levels of the page table and document the
expected semantics. Previously posting can be found at [0].
Changelog
RFC - v1
* Merge Patch 1 and 2 - preserve bisectability
* Drop RFC tag
Original cover letter follows...
The generic implementation of huge_pte_offset() has inconsistent
behaviour when looking up hugepage PUDs vs PMDs entries that are not
present (returning NULL vs pte_t*).
Similarly, it returns NULL when encountering swap entries although all
the callers have special checks to properly deal with swap entries.
Without clear semantics, it is difficult to determine if a change
breaks huge_pte_offset() without going through all the scenarios where
it is used.
I faced this recently when updating the arm64 implementation of
huge_pte_offset() to handle swap entries (related to enabling poisoned
memeory)[1]. And will come across again when I update it for
contiguous hugepage support now that core changes have been merged.
To address these issues, this following patch -
* makes huge_pte_offset() consistent between PUD and PMDs
* and, documents the expected behaviour of huge_pte_offset()
All feedback welcome.
Thanks,
Punit
[0] https://lkml.org/lkml/2017/7/24/514
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f02ab08afbe76ee7b0b2a34a9970e7dd200d8b01
Punit Agrawal (1):
mm/hugetlb: Make huge_pte_offset() consistent and document behaviour
mm/hugetlb.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
--
2.11.0
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next reply other threads:[~2017-07-25 15:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-25 15:41 Punit Agrawal [this message]
2017-07-25 15:41 ` [PATCH 1/1] mm/hugetlb: Make huge_pte_offset() consistent and document behaviour Punit Agrawal
2017-07-26 8:39 ` Catalin Marinas
2017-07-26 8:50 ` Michal Hocko
2017-07-26 8:53 ` Michal Hocko
2017-07-26 12:11 ` Punit Agrawal
2017-07-26 12:33 ` Michal Hocko
2017-07-26 12:47 ` Michal Hocko
2017-07-26 13:34 ` Punit Agrawal
2017-07-27 3:16 ` Mike Kravetz
2017-07-27 12:58 ` Punit Agrawal
2017-08-18 14:54 ` [PATCH v2] mm/hugetlb.c: make " Punit Agrawal
2017-08-18 21:29 ` Mike Kravetz
2017-08-21 18:07 ` Catalin Marinas
2017-08-21 21:30 ` Mike Kravetz
2017-08-22 15:32 ` Punit Agrawal
2017-08-22 10:11 ` Catalin Marinas
2017-08-30 7:49 ` Michal Hocko
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