The patch titled
Subject: mm/z3fold.c: fix z3fold_destroy_pool() ordering
has been added to the -mm tree. Its filename is
mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch
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------------------------------------------------------
From: Henry Burns <henryburns@xxxxxxxxxx>
Subject: mm/z3fold.c: fix z3fold_destroy_pool() ordering
The constraint from the zpool use of z3fold_destroy_pool() is there are no
outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in the
pool.
If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:
z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*
So compact_wq needs to be destroyed before release_wq.
Link: http://lkml.kernel.org/r/20190726224810.79660-1-henryburns@xxxxxxxxxx
Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vitaly Vul <vitaly.vul@xxxxxxxx>
Cc: Vitaly Wool <vitalywool@xxxxxxxxx>
Cc: Jonathan Adams <jwadams@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/z3fold.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/mm/z3fold.c~mm-z3foldc-fix-z3fold_destroy_pool-ordering
+++ a/mm/z3fold.c
@@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z
{
kmem_cache_destroy(pool->c_handle);
z3fold_unregister_migration(pool);
- destroy_workqueue(pool->release_wq);
+
+ /*
+ * We need to destroy pool->compact_wq before pool->release_wq,
+ * as any pending work on pool->compact_wq will call
+ * queue_work(pool->release_wq, &pool->work).
+ */
+
destroy_workqueue(pool->compact_wq);
+ destroy_workqueue(pool->release_wq);
kfree(pool);
}
_
Patches currently in -mm which might be from henryburns@xxxxxxxxxx are
mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch
mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch
