radix-tree: Partially disable memcg accounting in radix_tree_node_alloc() Having no preload, which turns accounting off for non-rt kernels, trying to allocate coming from shmem_fault() when memcg is full sends us scurrying off to pagefault_out_of_memory(), with dramatic (usually terminal) consequences. LTP's madvise06 testcase triggers this quite well, and per gitk, the below was the beginning of RT memcg woes. 58e698af4c63 radix-tree: account radix_tree_node to memory cgroup Turn memcg accounting off for RT in the problematic path. Signed-off-by: Mike Galbraith <efault@xxxxxx> Cc: stable-rt@xxxxxxxxxxxxxxx # +v4.6-rt --- lib/radix-tree.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -303,6 +303,13 @@ radix_tree_node_alloc(struct radix_tree_ if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) { struct radix_tree_preload *rtp; +#if defined(CONFIG_PREEMPT_RT_FULL) && defined(CONFIG_MEMCG) + /* + * Arriving here from shmem_fault() and meeting a full memcg + * will send us to pagefault_out_of_memory(), and a dead box. + */ + gfp_mask &= ~__GFP_ACCOUNT; +#endif /* * Even if the caller has preloaded, try to allocate from the * cache first for the new node to get accounted to the memory -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html