mm/madvise: drop range checks in madvise_free_single_vma()

Patch series "mm: cleanups around unmapping / zapping".

A bunch of cleanups around unmapping and zapping.  Mostly simplifications,
code movements, documentation and renaming of zapping functions.

With this series, we'll have the following high-level zap/unmap functions
(excluding high-level folio zapping):
* unmap_vmas() for actual unmapping (vmas will go away)
* zap_vma(): zap all page table entries in a vma
* zap_vma_for_reaping(): zap_vma() that must not block
* zap_vma_range(): zap a range of page table entries
* zap_vma_range_batched(): zap_vma_range() with more options and batching
* zap_special_vma_range(): limited zap_vma_range() for modules
* __zap_vma_range(): internal helper

Patch #1 is not about unmapping/zapping, but I stumbled over it while
verifying MADV_DONTNEED range handling.

Patch #16 is related to [1], but makes sense even independent of that.


This patch (of 16):

madvise_vma_behavior()->
madvise_dontneed_free()->madvise_free_single_vma() is only called from
madvise_walk_vmas()

(a) After try_vma_read_lock() confirmed that the whole range falls into
    a single VMA (see is_vma_lock_sufficient()).

(b) After adjusting the range to the VMA in the loop afterwards.

madvise_dontneed_free() might drop the MM lock when handling userfaultfd,
but it properly looks up the VMA again to adjust the range.

So in madvise_free_single_vma(), the given range should always fall into a
single VMA and should also span at least one page.

Let's drop the error checks.

The code now matches what we do in madvise_dontneed_single_vma(), where we
call zap_vma_range_batched() that documents: "The range must fit into one
VMA.".  Although that function still adjusts that range, we'll change that
soon.

Link: https://lkml.kernel.org/r/20260227200848.114019-1-david@kernel.org
Link: https://lkml.kernel.org/r/20260227200848.114019-2-david@kernel.org
Link: https://lore.kernel.org/r/aYSKyr7StGpGKNqW@google.com [1]
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Arve <arve@android.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Carlos Llamas <cmllamas@google.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: Dave Airlie <airlied@gmail.com>
Cc: David Ahern <dsahern@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Namhyung kim <namhyung@kernel.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Todd Kjos <tkjos@android.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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