f8572367ea
Commit 0cf18e839f64 of large folio zap work broke uffd-wp. Now mm's uffd unit test "wp-unpopulated" will trigger this WARN_ON_ONCE(). The WARN_ON_ONCE() asserts that an VMA cannot be registered with userfaultfd-wp if it contains a !normal page, but it's actually possible. One example is an anonymous vma, register with uffd-wp, read anything will install a zero page. Then when zap on it, this should trigger. What's more, removing that WARN_ON_ONCE may not be enough either, because we should also not rely on "whether it's a normal page" to decide whether pte marker is needed. For example, one can register wr-protect over some DAX regions to track writes when UFFD_FEATURE_WP_ASYNC enabled, in which case it can have page==NULL for a devmap but we may want to keep the marker around. Link: https://lkml.kernel.org/r/20240313213107.235067-1-peterx@redhat.com Fixes: 0cf18e839f64 ("mm/memory: handle !page case in zap_present_pte() separately") Signed-off-by: Peter Xu <peterx@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Muhammad Usama Anjum <usama.anjum@collabora.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.