The patch titled
Subject: mm:swap: do not check readahead flag with THP anon
has been added to the -mm tree. Its filename is
mm-swap-clean-up-swap-readahead-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-clean-up-swap-readahead-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-swap-clean-up-swap-readahead-fix.patch
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------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: mm:swap: do not check readahead flag with THP anon
Huang reported that the PG_readahead flag uses PF_NO_COMPOUND so that we
cannot use the flag for THP page. So, we need to check first whether the
page is THP 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.
Link: http://lkml.kernel.org/r/874lm83zho.fsf@xxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20180227232611.169883-1-minchan@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap_state.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff -puN mm/swap_state.c~mm-swap-clean-up-swap-readahead-fix mm/swap_state.c
--- a/mm/swap_state.c~mm-swap-clean-up-swap-readahead-fix
+++ a/mm/swap_state.c
@@ -338,12 +338,17 @@ struct page *lookup_swap_cache(swp_entry
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;
@@ -592,8 +597,7 @@ struct page *swapin_readahead(swp_entry_
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);
}
@@ -756,8 +760,7 @@ struct page *do_swap_page_readahead(swp_
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);
}
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
mm-swap-clean-up-swap-readahead.patch
mm-swap-clean-up-swap-readahead-fix.patch
mm-swap-unify-cluster-based-and-vma-based-swap-readahead.patch
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