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Instead of checking the poison flag only in the fast swap cache lookup path, always check the poison flags after locking a swap cache folio. There are two reasons to do so. The folio is unstable and could be removed from the swap cache anytime, so it's totally possible that the folio is no longer the backing folio of a swap entry, and could be an irrelevant poisoned folio. We might mistakenly kill a faulting process. And it's totally possible or even common for the slow swap in path (swapin_readahead) to bring in a cached folio. The cache folio could be poisoned, too. Only checking the poison flag in the fast path will miss such folios. The race window is tiny, so it's very unlikely to happen, though. While at it, also add a unlikely prefix. Link: https://lkml.kernel.org/r/20250916160100.31545-5-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Nhat Pham <nphamcs@gmail.com> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: kernel test robot <oliver.sang@intel.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Cc: SeongJae Park <sj@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.