[RFC PATCH 4/9] mm: zswap: move more same-filled pages checks outside of zswap_store()

Yosry Ahmed
2024-03-25T23:50:27Z

Currently, zswap_store() check zswap_same_filled_pages_enabled, kmaps
the folio, then calls zswap_is_page_same_filled() to check the folio
contents. Move this logic into zswap_is_page_same_filled() as well (and
rename it to use 'folio' while we are at it).

This makes zswap_store() cleaner, and makes following changes to that
logic contained within the helper.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
mm/zswap.c | 45 ++++++++++++++++++++++++---------------------
1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 6b890c8590ef7..498a6c5839bef 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1385,26 +1385,36 @@ static void shrink_worker(struct work_struct *w)
} while (zswap_total_pages() > thr);
}

-static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
+static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long *value)
{
unsigned long *page;
unsigned long val;
unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
+ bool ret;

- page = (unsigned long *)ptr;
+ if (!zswap_same_filled_pages_enabled)
+ return false;
+
+ page = kmap_local_folio(folio, 0);
val = page[0];

- if (val != page[last_pos])
- return 0;
+ if (val != page[last_pos]) {
+ ret = false;
+ goto out;
+ }

for (pos = 1; pos < last_pos; pos++) {
- if (val != page[pos])
- return 0;
+ if (val != page[pos]) {
+ ret = false;
+ goto out;
+ }
}

*value = val;
-
- return 1;
+ ret = true;
+out:
+ kunmap_local(page);
+ return ret;
}

static void zswap_fill_page(void *ptr, unsigned long value)
@@ -1438,6 +1448,7 @@ bool zswap_store(struct folio *folio)
struct obj_cgroup *objcg = NULL;
struct mem_cgroup *memcg = NULL;
struct zswap_entry *entry;
+ unsigned long value;

VM_WARN_ON_ONCE(!folio_test_locked(folio));
VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
@@ -1470,19 +1481,11 @@ bool zswap_store(struct folio *folio)
goto reject;
}

- if (zswap_same_filled_pages_enabled) {
- unsigned long value;
- u8 *src;
-
- src = kmap_local_folio(folio, 0);
- if (zswap_is_page_same_filled(src, &value)) {
- kunmap_local(src);
- entry->length = 0;
- entry->value = value;
- atomic_inc(&zswap_same_filled_pages);
- goto insert_entry;
- }
- kunmap_local(src);
+ if (zswap_is_folio_same_filled(folio, &value)) {
+ entry->length = 0;
+ entry->value = value;
+ atomic_inc(&zswap_same_filled_pages);
+ goto insert_entry;
}

if (!zswap_non_same_filled_pages_enabled)
--
2.44.0.396.g6e790dbe36-goog