Patch series "mm, swap: don't spin on a bad swap entry", v3. I've seen some machines at Meta fleet that show the following type of problem: 1) It gets some weird warning: BUG: Bad page map in process khugepaged pte:f000eef300000017 pmd:00000067 addr:00007f57c0a01000 vm_flags:20200073 anon_vma:ffff88829af7c340 mapping:0000000000000000 index:7f57c0a01 The corruption is most likely the collapse/PT_RECLAIM race fixed by commit 366a4532d96f ("mm: fix the race between collapse and PT_RECLAIM under per-vma lock"). But this series is not about this one. 2) Then the fault never makes progress. do_swap_page() returns 0 when get_swap_device() fails, so the fault is retried, reads the same entry and faults again. Nothing in the round trip changes the PTE, and the same line comes out on every pass: get_swap_device: Bad swap offset entry 3ffffffc043c5 Patch 1 makes get_swap_device() return ERR_PTR(-EIO) for a malformed entry, keeping NULL for a device swapoff is taking away, and converts the callers. No functional change expected. Patch 2 uses that to return VM_FAULT_SIGBUS instead of retrying. This patch (of 2): get_swap_device() returns NULL for two different things: an entry whose type names no swap device or whose offset is past the end of one, and a device that swapoff is taking away. The first never becomes valid, the second does, and callers cannot tell them apart. Return ERR_PTR(-EIO) for the two malformed cases and keep NULL for swapoff. copy_nonpresent_pte() already reports -EIO for an entry whose type names no device. Callers bail out on failure either way, so switch them to IS_ERR_OR_NULL(), and let the two paths that drop the reference skip an error pointer. No functional change. Link: https://lore.kernel.org/20260818-swap-v3-0-d3fa52598a59@debian.org Link: https://lore.kernel.org/20260818-swap-v3-1-d3fa52598a59@debian.org Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: Kairui Song <kasong@tencent.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <baoquan.he@linux.dev> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Chris Li <chrisl@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jann Horn <jannh@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Liam R. Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Pedro Falcato <pfalcato@suse.de> Cc: Peter Xu <peterx@redhat.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@kernel.org>