linux-kernel - [PATCH 0/5] Clean up huge vmap and ioremap code

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Date:   Wed, 12 Sep 2018 11:26:09 +0100
From:   Will Deacon <will.deacon@....com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     cpandya@...eaurora.org, toshi.kani@....com, tglx@...utronix.de,
        mhocko@...e.com, akpm@...ux-foundation.org,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 0/5] Clean up huge vmap and ioremap code

Hi all,

The recent introduction of break-before-make on the huge vmap path in
b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table")
introduced a pair of arch functions for freeing a child level of page
table before putting down a huge mapping at the parent level.

Whilst this works well, the semantics of the pXd_free_pYd_table() function
are slightly confusing, and this led to an over-eager VM_WARN_ON in the
arm64 code that we fixed in -rc3 [1]. Linus suggested that the interface
could be tidied up so that the pXd_present() checks are moved into the
caller, so I've implemented that and generally cleaned up the ioremap code
so that it's easier to follow. I also extended the break-before-make code
to cover the huge p4d case, although this remains unused by any architectures.

Feedback welcome.

Cheers,

Will

[1] https://lkml.org/lkml/2018/9/7/898

--->8

Will Deacon (5):
  ioremap: Rework pXd_free_pYd_page() API
  arm64: mmu: Drop pXd_present() checks from pXd_free_pYd_table()
  x86: pgtable: Drop pXd_none() checks from pXd_free_pYd_table()
  lib/ioremap: Ensure phys_addr actually corresponds to a physical
    address
  lib/ioremap: Ensure break-before-make is used for huge p4d mappings

 arch/arm64/mm/mmu.c           |  13 +++---
 arch/x86/mm/pgtable.c         |  14 +++---
 include/asm-generic/pgtable.h |   5 ++
 lib/ioremap.c                 | 103 +++++++++++++++++++++++++++++-------------
 4 files changed, 91 insertions(+), 44 deletions(-)

-- 
2.1.4