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[7/8] rcu/kvfree: Make fill page cache start from krcp->nr_bkv_objs

Message ID 20230510170242.2187714-7-paulmck@kernel.org (mailing list archive)
State Mainlined
Commit 60888b77a06ea16665e4df980bb86b418253e268
Headers show
Series kvfree_rcu() changes for v6.5 | expand

Commit Message

Paul E. McKenney May 10, 2023, 5:02 p.m. UTC 
From: Zqiang <qiang1.zhang@intel.com>

When the fill_page_cache_func() function is invoked, it assumes that
the cache of pages is completely empty.  However, there can be some time
between triggering execution of this function and its actual invocation.
During this time, kfree_rcu_work() might run, and might fill in part or
all of this cache of pages, thus invalidating the fill_page_cache_func()
function's assumption.

This will not overfill the cache because put_cached_bnode() will reject
the extra page.  However, it will result in a needless allocation and
freeing of one extra page, which might not be helpful under lowish-memory
conditions.

This commit therefore causes the fill_page_cache_func() to explicitly
account for pages that have been placed into the cache shortly before
it starts running.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 18f592bf6dc6..98f2e833e217 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3201,7 +3201,7 @@  static void fill_page_cache_func(struct work_struct *work)
 	nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ?
 		1 : rcu_min_cached_objs;
 
-	for (i = 0; i < nr_pages; i++) {
+	for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) {
 		bnode = (struct kvfree_rcu_bulk_data *)
 			__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);