selftests/mm: make file helpers return errors

Patch series "selftests/mm: separate GUP microbenchmarking from functional
testing", v11.

gup_test.c currently serves two separate purposes: benchmarking
(GUP_FAST_BENCHMARK, PIN_FAST_BENCHMARK and PIN_LONGTERM_BENCHMARK) and
functional testing (GUP_BASIC_TEST, PIN_BASIC_TEST and
DUMP_USER_PAGES_TEST).  Keeping both in one program makes the functional
tests harder to run and report individually, while run_vmtests.sh has to
invoke the program repeatedly with different options.

Separate these roles into tools/mm/gup_bench for benchmarking and
tools/testing/selftests/mm/gup for functional testing.  Move the shared
file and hugepage helpers to tools/lib/mm/ so both programs can use them
without duplicating the implementation.

Patch 1 makes read_file(), write_file(), read_num(), write_num() and
write_num_ignore_einval() return errors to their callers instead of
exiting.  It also makes read_num() reject negative and malformed values
and updates the existing callers to handle failures.

Patch 2 moves these file helpers from vm_util.c to tools/lib/mm/.  It
keeps them available to the mm selftests through vm_util.h and adjusts the
selftests build accordingly.

Patch 3 moves hugepage_settings.[ch] from selftests/mm to tools/lib/mm/. 
It also removes its kselftest dependency while preserving TAP-compatible
diagnostics for selftest users.

Patch 4 moves the existing gup_test implementation from selftests/mm to
tools/mm as gup_bench.  This keeps the code movement separate from the
subsequent changes and makes it easier to review.

Patch 5 removes the functional test modes and kselftest dependency from
gup_bench.  When run without arguments, it performs one GUP_FAST benchmark
using the existing defaults instead of running the whole matrix.  Other
benchmark configurations can be selected through command-line options.

Patch 6 adds a new harness-based GUP selftest.  It covers THP, non-THP and
HugeTLB mappings across private/shared and read/write variants.  For each
variant, it tests get_user_pages(), get_user_pages_fast(),
pin_user_pages(), pin_user_pages_fast() and long-term pinning modes using
four batch sizes.  The HugeTLB variants share a one-time setup of two
hugeTLB pages.


This patch (of 6):

Change read_file(), write_file(), read_num(), write_num() and
write_num_ignore_einval() in vm_util.c to report failures to callers
instead of exiting from the helper.

Make read_file() return a negative errno on failure and 0 on success, so
callers can distinguish a successful read from an I/O error.  Also make
read_num() reject negative and malformed values.

Keep write_num_ignore_einval() silent for -EINVAL while returning other
errors to its caller.

Update callers to print diagnostics and fail wherever required.  Modify a
comment which implies write_num() uses ksft_exit_fail_msg().  Also add a
helper print_file_access_error() in hugepage_settings.c to print
TAP-compatible errors without a kselftest dependency.  This prepares the
helpers to be moved to tools/lib/mm without a kselftest dependency.

[sarthak.sharma@arm.com: convert hugetlb_nr_resv_pages()]
  Link: https://lore.kernel.org/937939c3-ae9a-4148-a601-0f8876216423@arm.com
Link: https://lore.kernel.org/20260918112234.195857-1-sarthak.sharma@arm.com
Link: https://lore.kernel.org/20260918112234.195857-2-sarthak.sharma@arm.com
Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>

0 files changed, 0 insertions, 0 deletions