When unmapping VMA pages, pages will be gathered in batch and released by tlb_finish_mmu() if CONFIG_MMU_GATHER_NO_GATHER is not set. The function tlb_finish_mmu() is responsible for calling free_pages_and_swap_cache(), which calls lru_add_drain() to drain cached pages in folio_batch before releasing gathered pages. Thus, it is redundant to call lru_add_drain() before gathering pages, if CONFIG_MMU_GATHER_NO_GATHER is not set. Remove lru_add_drain() prior to gathering and unmapping pages in exit_mmap() and unmap_region() if CONFIG_MMU_GATHER_NO_GATHER is not set. Note that the page unmapping process in oom_killer (e.g., in __oom_reap_task_mm()) also uses tlb_finish_mmu() and does not have redundant lru_add_drain(). So, this commit makes the code more consistent. Signed-off-by: Jianfeng Wang <jianfeng.w.wang@xxxxxxxxxx> --- mm/mmap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index 1971bfffcc03..da0308eef435 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2330,7 +2330,10 @@ static void unmap_region(struct mm_struct *mm, struct ma_state *mas, struct mmu_gather tlb; unsigned long mt_start = mas->index; + /* Defer lru_add_drain() to tlb_finish_mmu() for the ifndef case. */ +#ifdef CONFIG_MMU_GATHER_NO_GATHER lru_add_drain(); +#endif tlb_gather_mmu(&tlb, mm); update_hiwater_rss(mm); unmap_vmas(&tlb, mas, vma, start, end, tree_end, mm_wr_locked); @@ -3300,7 +3303,10 @@ void exit_mmap(struct mm_struct *mm) return; } + /* Defer lru_add_drain() to tlb_finish_mmu() for the ifndef case. */ +#ifdef CONFIG_MMU_GATHER_NO_GATHER lru_add_drain(); +#endif flush_cache_mm(mm); tlb_gather_mmu_fullmm(&tlb, mm); /* update_hiwater_rss(mm) here? but nobody should be looking */ -- 2.42.1
