linux-kernel - [PATCH 0/2] fix for direct-I/O to DAX mappings

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Message-ID: <148804250784.36605.12832323062093584440.stgit@dwillia2-desk3.amr.corp.intel.com>
Date:   Sat, 25 Feb 2017 09:08:28 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     x86@...nel.org, Xiong Zhou <xzhou@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        torvalds@...ux-foundation.org,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: [PATCH 0/2] fix for direct-I/O to DAX mappings

Hi Andrew,

While Ross was doing a review of a new mmap+DAX direct-I/O test case for
xfstests, from Xiong, he noticed occasions where it failed to trigger a
page dirty event.  Dave then spotted the problem fixed by patch1. The
pte_devmap() check is precluding pte_allows_gup(), i.e. bypassing
permission checks and dirty tracking.

Patch2 is a cleanup and clarifies that pte_unmap() only needs to be done
once per page-worth of ptes. It unifies the exit paths similar to the
generic gup_pte_range() in the __HAVE_ARCH_PTE_SPECIAL case.

I'm sending this through the -mm tree for a double-check from memory
management folks. It has a build success notification from the kbuild
robot.

---

Dan Williams (2):
      x86, mm: fix gup_pte_range() vs DAX mappings
      x86, mm: unify exit paths in gup_pte_range()

 arch/x86/mm/gup.c |   37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)