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a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=2OwXVqhp2XgA:10 a=GoEa3M9JfhUA:10 a=20KFwNOVAAAA:8 a=-UZBVonvdr6tOHmRkHYA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: BbHVXmOSppuLvXg_3ypttL6yLXJ9fC1A X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODE5MDE5NyBTYWx0ZWRfX92SI1Cpe3vH6 Py9rcHmION0eCkS1If5jIgPraxGjXLwWu6z1Moo2coiavfO0ep7dvwuZeH1npnIjPeL1NnpglTG 8lJoxv7hdVGz37wGFz8dHaHbBbQJw+JL1oXk+wM1n9E0RmeFOpN6hL+1qLXoHNwMYGwERjBEu27 jwpRZnjf4KnLHfUskqabpmBdu/sP2XmoWO6r6uWlXE7F/XIojrzP6J36pSKXkzQEMJTffZ1pp6b iwG4PAjpOR48t1q5Jdt395HWJyP13aNXVtAAI4wkLZqeUymGni3+0kge8ztOeqLXH+iNJeCc9TP d7W7AE7OuB44Ty0ygBt6Mdv4WuWK71ft9tO0y3vjX6xP8TdbzQOnXadnQ9r5UwYK+YikJbCU9XR VpoiSfBbrEzvWeG/J1ie9ADRo8P93Q== On Tue, Aug 19, 2025 at 07:42:00AM -0600, Nico Pache wrote: > There are cases where, if an attempted collapse fails, all subsequent > orders are guaranteed to also fail. Avoid these collapse attempts by > bailing out early. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 31 ++++++++++++++++++++++++++++++- > 1 file changed, 30 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 6a4cf7e4a7cc..7d9b5100bea1 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1389,10 +1389,39 @@ static int collapse_scan_bitmap(struct mm_struct *mm, unsigned long address, > ret = collapse_huge_page(mm, address, referenced, unmapped, > cc, mmap_locked, order, > offset * KHUGEPAGED_MIN_MTHP_NR); > - if (ret == SCAN_SUCCEED) { > + > + /* > + * Analyze failure reason to determine next action: > + * - goto next_order: try smaller orders in same region > + * - continue: try other regions at same order > + * - break: stop all attempts (system-wide failure) > + */ > + switch (ret) { > + /* Cases were we should continue to the next region */ > + case SCAN_SUCCEED: > collapsed += (1 << order); Yeah as bot noticed (and clang locally) This needs a break or fallthrough. > + case SCAN_PAGE_RO: > + case SCAN_PTE_MAPPED_HUGEPAGE: > continue; > + /* Cases were lower orders might still succeed */ > + case SCAN_LACK_REFERENCED_PAGE: > + case SCAN_EXCEED_NONE_PTE: > + case SCAN_EXCEED_SWAP_PTE: > + case SCAN_EXCEED_SHARED_PTE: > + case SCAN_PAGE_LOCK: > + case SCAN_PAGE_COUNT: > + case SCAN_PAGE_LRU: > + case SCAN_PAGE_NULL: > + case SCAN_DEL_PAGE_LRU: > + case SCAN_PTE_NON_PRESENT: > + case SCAN_PTE_UFFD_WP: > + case SCAN_ALLOC_HUGE_PAGE_FAIL: > + goto next_order; > + /* All other cases should stop collapse attempts */ > + default: > + break; Wouldn't it be better to not have this so the compiler asserts that you have all cases listed here? > } > + break; > } > > next_order: > -- > 2.50.1 >