In kfree_rcu() headless implementation (where the caller need not pass an rcu_head, but rather directly pass a pointer to an object), we have a fall-back where we allocate a rcu_head wrapper for the caller (not the common case). This brings the pattern of needing to allocate some memory to free some memory. Currently we use GFP_ATOMIC flag to try harder for this allocation, however the GFP_MEMALLOC flag is more tailored to this pattern. We need to try harder not only during atomic context, but also during non-atomic context anyway. So use the GFP_MEMALLOC flag instead. Also remove the __GFP_NOWARN flag simply because although we do have a synchronize_rcu() fallback for absolutely worst case, we still would like to not enter that path and atleast trigger a warning to the user. Cc: linux-mm@xxxxxxxxx Cc: rcu@xxxxxxxxxxxxxxx Cc: willy@xxxxxxxxxxxxx Cc: peterz@xxxxxxxxxxxxx Cc: neilb@xxxxxxxx Cc: vbabka@xxxxxxx Cc: mgorman@xxxxxxx Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> --- This patch is based on the (not yet upstream) code in: git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git (branch rcu/kfree) It is a follow-up to the posted series: https://lore.kernel.org/lkml/20200330023248.164994-1-joel@xxxxxxxxxxxxxxxxx/ kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4be763355c9fb..965deefffdd58 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3149,7 +3149,7 @@ static inline struct rcu_head *attach_rcu_head_to_object(void *obj) if (!ptr) ptr = kmalloc(sizeof(unsigned long *) + - sizeof(struct rcu_head), GFP_ATOMIC | __GFP_NOWARN); + sizeof(struct rcu_head), GFP_MEMALLOC); if (!ptr) return NULL; -- 2.26.0.rc2.310.g2932bb562d-goog
