selftests/memfd_secret: add vmsplice() test

Let's add a simple reproducer for a scenario where GUP-fast could succeed
on secretmem folios, making vmsplice() succeed instead of failing. The
reproducer is based on a reproducer [1] by Miklos Szeredi.

We want to perform two tests: vmsplice() when a fresh page was just
faulted in, and vmsplice() on an existing page after munmap() that would
drain certain LRU caches/batches in the kernel.

In an ideal world, we could use fallocate(FALLOC_FL_PUNCH_HOLE) /
MADV_REMOVE to remove any existing page. As that is currently not
possible, run the test before any other tests that would allocate memory
in the secretmem fd.

Perform the ftruncate() only once, and check the return value.

[1] https://lkml.kernel.org/r/CAJfpegt3UCsMmxd0taOY11Uaw5U=eS1fE5dn0wZX3HF0oy8-oQ@mail.gmail.com

Link: https://lkml.kernel.org/r/20240326143210.291116-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: xingwei lee <xrivendell7@gmail.com>
Cc: yue sun <samsun1006219@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftests: secretmem: floor the memory size to the multiple of page_size

The "locked-in-memory size" limit per process can be non-multiple of
page_size. The mmap() fails if we try to allocate locked-in-memory with
same size as the allowed limit if it isn't multiple of the page_size
because mmap() rounds off the memory size to be allocated to next multiple
of page_size.

Fix this by flooring the length to be allocated with mmap() to the
previous multiple of the page_size.

This was getting triggered on KernelCI regularly because of different
ulimit settings which wasn't multiple of the page_size. Find logs
here: https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/
The bug in was present from the time test was first added.

Link: https://lkml.kernel.org/r/20231214101931.1155586-1-usama.anjum@collabora.com
Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Closes: https://linux.kernelci.org/test/plan/id/657654bd8e81e654fae13532/
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftests/vm: rename selftests/vm to selftests/mm

Rename selftets/vm to selftests/mm for being more consistent with the
code, documentation, and tools directories, and won't be confused with
virtual machines.

[sj@kernel.org: convert missing vm->mm changes]
Link: https://lkml.kernel.org/r/20230107230643.252273-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230103180754.129637-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>