Huang reported PG_readahead flag marked PF_NO_COMPOUND so that we cannot use the flag for THP page. So, we need to check first whether page is THP or not before using TestClearPageReadahead in lookup_swap_cache.
This patch fixes it. Furthermore, swap_[cluster|vma]_readahead cannot mark PG_readahead for newly allocated page because the allocated page is always a normal page, not THP at this moment. So let's clean it up, too. Cc: Hugh Dickins <[email protected]> Cc: "Huang, Ying" <[email protected]> Signed-off-by: Minchan Kim <[email protected]> --- mm/swap_state.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 8dde719e973c..1c4ac3220f41 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -348,12 +348,17 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma, INC_CACHE_INFO(find_total); if (page) { bool vma_ra = swap_use_vma_readahead(); - bool readahead = TestClearPageReadahead(page); + bool readahead; INC_CACHE_INFO(find_success); + /* + * At the moment, we don't support PG_readahead for anon THP + * so let's bail out rather than confusing the readahead stat. + */ if (unlikely(PageTransCompound(page))) return page; + readahead = TestClearPageReadahead(page); if (vma && vma_ra) { unsigned long ra_val; int win, hits; @@ -608,8 +613,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, continue; if (page_allocated) { swap_readpage(page, false); - if (offset != entry_offset && - likely(!PageTransCompound(page))) { + if (offset != entry_offset) { SetPageReadahead(page); count_vm_event(SWAP_RA); } @@ -772,8 +776,7 @@ struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, continue; if (page_allocated) { swap_readpage(page, false); - if (i != ra_info.offset && - likely(!PageTransCompound(page))) { + if (i != ra_info.offset) { SetPageReadahead(page); count_vm_event(SWAP_RA); } -- 2.16.2.395.g2e18187dfd-goog
