The patch titled
Subject: mm/zswap: refactor zswap_store_page()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-zswap-fix-inconsistency-when-zswap_store_page-fails-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-fix-inconsistency-when-zswap_store_page-fails-fix.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Subject: mm/zswap: refactor zswap_store_page()
Date: Fri, 31 Jan 2025 17:20:37 +0900
Change zswap_store_page() to return a boolean value, where true indicates
the page is successfully stored in zswap, and false otherwise.
Since zswap_store_page() no longer returns the size of the entry,
remove 'bytes' variable from zswap_store(), and jump to the put_pool label
when it fails.
Move the objcg charging and the incrementing of zswap_store_pages just
after the tree store is successful. At that point, there's no chance of
failure, and the freeing path will certainly uncharge zswap memory and
decrement the counter.
Link: https://lkml.kernel.org/r/20250131082037.2426-1-42.hyeyoo@xxxxxxxxx
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Suggested-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
--- a/mm/zswap.c~mm-zswap-fix-inconsistency-when-zswap_store_page-fails-fix
+++ a/mm/zswap.c
@@ -1445,9 +1445,9 @@ resched:
* main API
**********************************/
-static ssize_t zswap_store_page(struct page *page,
- struct obj_cgroup *objcg,
- struct zswap_pool *pool)
+static bool zswap_store_page(struct page *page,
+ struct obj_cgroup *objcg,
+ struct zswap_pool *pool)
{
swp_entry_t page_swpentry = page_swap_entry(page);
struct zswap_entry *entry, *old;
@@ -1456,7 +1456,7 @@ static ssize_t zswap_store_page(struct p
entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page));
if (!entry) {
zswap_reject_kmemcache_fail++;
- return -EINVAL;
+ return false;
}
if (!zswap_compress(page, entry, pool))
@@ -1483,13 +1483,17 @@ static ssize_t zswap_store_page(struct p
/*
* The entry is successfully compressed and stored in the tree, there is
- * no further possibility of failure. Grab refs to the pool and objcg.
- * These refs will be dropped by zswap_entry_free() when the entry is
- * removed from the tree.
+ * no further possibility of failure. Grab refs to the pool and objcg,
+ * charge zswap memory, and increment zswap_stored_pages.
+ * The opposite actions will be performed by zswap_entry_free()
+ * when the entry is removed from the tree.
*/
zswap_pool_get(pool);
- if (objcg)
+ if (objcg) {
obj_cgroup_get(objcg);
+ obj_cgroup_charge_zswap(objcg, entry->length);
+ }
+ atomic_long_inc(&zswap_stored_pages);
/*
* We finish initializing the entry while it's already in xarray.
@@ -1504,22 +1508,19 @@ static ssize_t zswap_store_page(struct p
entry->pool = pool;
entry->swpentry = page_swpentry;
entry->objcg = objcg;
- if (objcg)
- obj_cgroup_charge_zswap(objcg, entry->length);
entry->referenced = true;
if (entry->length) {
INIT_LIST_HEAD(&entry->lru);
zswap_lru_add(&zswap_list_lru, entry);
}
- atomic_long_inc(&zswap_stored_pages);
- return entry->length;
+ return true;
store_failed:
zpool_free(pool->zpool, entry->handle);
compress_failed:
zswap_entry_cache_free(entry);
- return -EINVAL;
+ return false;
}
bool zswap_store(struct folio *folio)
@@ -1566,10 +1567,8 @@ bool zswap_store(struct folio *folio)
for (index = 0; index < nr_pages; ++index) {
struct page *page = folio_page(folio, index);
- ssize_t bytes;
- bytes = zswap_store_page(page, objcg, pool);
- if (bytes < 0)
+ if (!zswap_store_page(page, objcg, pool))
goto put_pool;
}
_
Patches currently in -mm which might be from 42.hyeyoo@xxxxxxxxx are
mm-zsmalloc-add-__maybe_unused-attribute-for-is_first_zpdesc.patch
mm-zswap-fix-inconsistency-when-zswap_store_page-fails.patch
mm-zswap-fix-inconsistency-when-zswap_store_page-fails-fix.patch
