linux-kernel - [PATCH v2 0/4] various improvements to the GUP interface

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Date:   Tue,  3 Oct 2023 00:14:50 +0100
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH v2 0/4] various improvements to the GUP interface

A series of fixes to simplify and improve the GUP interface with an eye to
providing groundwork to future improvements:-

* __access_remote_vm() and access_remote_vm() are functionally identical,
  so make the former static such that in future we can potentially change
  the external-facing implementation details of this function.

* Extend is_valid_gup_args() to cover the missing FOLL_TOUCH case, and
  simplify things by defining INTERNAL_GUP_FLAGS to check against.

* Adjust __get_user_pages_locked() to explicitly treat a failure to pin any
  pages as an error in all circumstances other than FOLL_NOWAIT being
  specified, bringing it in line with the nommu implementation of this
  function.

* (With many thanks to Arnd who suggested this in the first instance)
  Update get_user_page_vma_remote() to explicitly only return a page or an
  error, simplifying the interface and avoiding the questionable
  IS_ERR_OR_NULL() pattern.

v2:
* Corrected spelling mistakes in patches 1 and 2 (thanks PeterZ).
* Made things WARN_ON_ONCE() where appropriate and dropped unnecessary
  checks (thanks David).

v1:
https://lore.kernel.org/all/cover.1696174961.git.lstoakes@gmail.com/

Lorenzo Stoakes (4):
  mm: make __access_remote_vm() static
  mm/gup: explicitly define and check internal GUP flags, disallow
    FOLL_TOUCH
  mm/gup: make failure to pin an error if FOLL_NOWAIT not specified
  mm/gup: adapt get_user_page_vma_remote() to never return NULL

 arch/arm64/kernel/mte.c |  4 ++--
 include/linux/mm.h      | 14 +++++++++-----
 kernel/events/uprobes.c |  4 ++--
 kernel/ptrace.c         |  2 +-
 mm/gup.c                | 16 +++++++++++++---
 mm/internal.h           |  3 +++
 mm/memory.c             |  7 +++----
 mm/nommu.c              |  4 ++--
 8 files changed, 35 insertions(+), 19 deletions(-)

--
2.42.0