8b671fe1a8
evict_folios() uses a second pass to reclaim folios that have gone through page writeback and become clean before it finishes the first pass, since folio_rotate_reclaimable() cannot handle those folios due to the isolation. The second pass tries to avoid potential double counting by deducting scan_control->nr_scanned. However, this can result in underflow of nr_scanned, under a condition where shrink_folio_list() does not increment nr_scanned, i.e., when folio_trylock() fails. The underflow can cause the divisor, i.e., scale=scanned+reclaimed in vmpressure_calc_level(), to become zero, resulting in the following crash: [exception RIP: vmpressure_work_fn+101] process_one_work at ffffffffa3313f2b Since scan_control->nr_scanned has no established semantics, the potential double counting has minimal risks. Therefore, fix the problem by not deducting scan_control->nr_scanned in evict_folios(). Link: https://lkml.kernel.org/r/20240711191957.939105-1-yuzhao@google.com Fixes: 359a5e1416ca ("mm: multi-gen LRU: retry folios written back while isolated") Reported-by: Wei Xu <weixugc@google.com> Signed-off-by: Yu Zhao <yuzhao@google.com> Cc: Alexander Motin <mav@ixsystems.com> Cc: <stable@vger.kernel.org> 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.