linux-kernel - [PATCH 2/2] zsmalloc: move migration destination zspage inuse check

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Message-ID: <20230623044016.366793-3-senozhatsky@chromium.org>
Date:   Fri, 23 Jun 2023 13:40:02 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCH 2/2] zsmalloc: move migration destination zspage inuse check

Destination zspage fullness check need to be done after
zs_object_copy() because that's where source and destination
zspages fullness change.  Checking destination zspage fullness
before zs_object_copy() may cause migration to loop through
source zspage sub-pages scanning for allocate objects just to
find out at the end that the destination zspage is full.

Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 mm/zsmalloc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5d60eaedc3b7..4a84f7877669 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1620,10 +1620,6 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
 			continue;
 		}
 
-		/* Stop if there is no more space */
-		if (zspage_full(class, get_zspage(d_page)))
-			break;
-
 		used_obj = handle_to_obj(handle);
 		free_obj = obj_malloc(pool, get_zspage(d_page), handle);
 		zs_object_copy(class, free_obj, used_obj);
@@ -1631,6 +1627,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		record_obj(handle, free_obj);
 		obj_free(class->size, used_obj);
 
+		/* Stop if there is no more space */
+		if (zspage_full(class, get_zspage(d_page)))
+			break;
+
 		/* Stop if there are no more objects to migrate */
 		if (zspage_empty(get_zspage(s_page)))
 			break;
-- 
2.41.0.162.gfafddb0af9-goog