linux-kernel - [PATCH] kpageflags: respect folio head-page flag placement

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Date:   Wed, 25 Oct 2023 16:12:37 -0400
From:   Gregory Price <gourry.memverge@...il.com>
To:     linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, willy@...radead.org, david@...hat.com,
        vbabka@...e.cz, naoya.horiguchi@...ux.dev,
        linux-kernel@...r.kernel.org,
        Gregory Price <gregory.price@...verge.com>
Subject: [PATCH] kpageflags: respect folio head-page flag placement

kpageflags reads page-flags directly from the page, even when the
respective flag is only updated on the headpage of a folio.

Update bitchecks to use PAGEFLAG() interfaces to check folio for the
referenced, dirty, lru, active, and unevictable bits.

Signed-off-by: Gregory Price <gregory.price@...verge.com>
---
 fs/proc/page.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 195b077c0fac..958fb2311108 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -188,20 +188,31 @@ u64 stable_page_flags(struct page *page)
 		u |= 1 << KPF_SLAB;
 
 	u |= kpf_copy_bit(k, KPF_ERROR,		PG_error);
-	u |= kpf_copy_bit(k, KPF_DIRTY,		PG_dirty);
+
+	if (PageDirty(page))
+		u |= 1 << KPF_DIRTY;
+
 	u |= kpf_copy_bit(k, KPF_UPTODATE,	PG_uptodate);
 	u |= kpf_copy_bit(k, KPF_WRITEBACK,	PG_writeback);
 
-	u |= kpf_copy_bit(k, KPF_LRU,		PG_lru);
-	u |= kpf_copy_bit(k, KPF_REFERENCED,	PG_referenced);
-	u |= kpf_copy_bit(k, KPF_ACTIVE,	PG_active);
+	if (PageLRU(page))
+		u |= 1 << KPF_LRU;
+
+	if (PageReferenced(page))
+		u |= 1 << KPF_REFERENCED;
+
+	if (PageActive(page))
+		u |= 1 << KPF_ACTIVE;
+
 	u |= kpf_copy_bit(k, KPF_RECLAIM,	PG_reclaim);
 
 	if (PageSwapCache(page))
 		u |= 1 << KPF_SWAPCACHE;
 	u |= kpf_copy_bit(k, KPF_SWAPBACKED,	PG_swapbacked);
 
-	u |= kpf_copy_bit(k, KPF_UNEVICTABLE,	PG_unevictable);
+	if (PageUnevictable(page))
+		u |= 1 << KPF_UNEVICTABLE;
+
 	u |= kpf_copy_bit(k, KPF_MLOCKED,	PG_mlocked);
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.39.1