From 59bfbcf01967d4d3370a2b8294673dd709e732cc Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 13 Mar 2013 14:59:49 -0700 Subject: [PATCH] idr: idr_alloc() shouldn't trigger lowmem warning when preloaded GFP_NOIO is often used for idr_alloc() inside preloaded section as the allocation mask doesn't really matter. If the idr tree needs to be expanded, idr_alloc() first tries to allocate using the specified allocation mask and if it fails falls back to the preloaded buffer. This order prevent non-preloading idr_alloc() users from taking advantage of preloading ones by using preload buffer without filling it shifting the burden of allocation to the preload users. Unfortunately, this allowed/expected-to-fail kmem_cache allocation ends up generating spurious slab lowmem warning before succeeding the request from the preload buffer. This patch makes idr_layer_alloc() add __GFP_NOWARN to the first kmem_cache attempt and try kmem_cache again w/o __GFP_NOWARN after allocation from preload_buffer fails so that lowmem warning is generated if not suppressed by the original @gfp_mask. Signed-off-by: Tejun Heo Reported-by: David Teigland Tested-by: David Teigland Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/idr.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index c6fb8295507b..322e2816f2fb 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -106,8 +106,14 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr) if (layer_idr) return get_from_free_list(layer_idr); - /* try to allocate directly from kmem_cache */ - new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); + /* + * Try to allocate directly from kmem_cache. We want to try this + * before preload buffer; otherwise, non-preloading idr_alloc() + * users will end up taking advantage of preloading ones. As the + * following is allowed to fail for preloaded cases, suppress + * warning this time. + */ + new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN); if (new) return new; @@ -115,18 +121,24 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr) * Try to fetch one from the per-cpu preload buffer if in process * context. See idr_preload() for details. */ - if (in_interrupt()) - return NULL; - - preempt_disable(); - new = __this_cpu_read(idr_preload_head); - if (new) { - __this_cpu_write(idr_preload_head, new->ary[0]); - __this_cpu_dec(idr_preload_cnt); - new->ary[0] = NULL; + if (!in_interrupt()) { + preempt_disable(); + new = __this_cpu_read(idr_preload_head); + if (new) { + __this_cpu_write(idr_preload_head, new->ary[0]); + __this_cpu_dec(idr_preload_cnt); + new->ary[0] = NULL; + } + preempt_enable(); + if (new) + return new; } - preempt_enable(); - return new; + + /* + * Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so + * that memory allocation failure warning is printed as intended. + */ + return kmem_cache_zalloc(idr_layer_cache, gfp_mask); } static void idr_layer_rcu_free(struct rcu_head *head)