linux-kernel - [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in blkcg

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Date:   Mon, 21 Nov 2016 18:03:32 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        Michal Hocko <mhocko@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marc MERLIN <marc@...lins.org>
Subject: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in
 blkcg

blkcg allocates some per-cgroup data structures with GFP_NOWAIT and
when that fails falls back to operations which aren't specific to the
cgroup.  Occassional failures are expected under pressure and falling
back to non-cgroup operation is the right thing to do.

Unfortunately, I forgot to add __GFP_NOWARN to these allocations and
these expected failures end up creating a lot of noise.  Add
__GFP_NOWARN.

Signed-off-by: Tejun Heo <tj@...nel.org>
Reported-by: Marc MERLIN <marc@...lins.org>
Reported-by: Vlastimil Babka <vbabka@...e.cz>
---
 block/blk-cgroup.c  |    9 +++++----
 block/cfq-iosched.c |    3 ++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b08ccbb..8ba0af7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -185,7 +185,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	}
 
 	wb_congested = wb_congested_get_create(&q->backing_dev_info,
-					       blkcg->css.id, GFP_NOWAIT);
+					       blkcg->css.id,
+					       GFP_NOWAIT | __GFP_NOWARN);
 	if (!wb_congested) {
 		ret = -ENOMEM;
 		goto err_put_css;
@@ -193,7 +194,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 
 	/* allocate */
 	if (!new_blkg) {
-		new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT);
+		new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN);
 		if (unlikely(!new_blkg)) {
 			ret = -ENOMEM;
 			goto err_put_congested;
@@ -1022,7 +1023,7 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 	}
 
 	spin_lock_init(&blkcg->lock);
-	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
+	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
 #ifdef CONFIG_CGROUP_WRITEBACK
 	INIT_LIST_HEAD(&blkcg->cgwb_list);
@@ -1240,7 +1241,7 @@ int blkcg_activate_policy(struct request_queue *q,
 		if (blkg->pd[pol->plid])
 			continue;
 
-		pd = pol->pd_alloc_fn(GFP_NOWAIT, q->node);
+		pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q->node);
 		if (!pd)
 			swap(pd, pd_prealloc);
 		if (!pd) {
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5e24d88..b4c3b6c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3854,7 +3854,8 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
 			goto out;
 	}
 
-	cfqq = kmem_cache_alloc_node(cfq_pool, GFP_NOWAIT | __GFP_ZERO,
+	cfqq = kmem_cache_alloc_node(cfq_pool,
+				     GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN,
 				     cfqd->queue->node);
 	if (!cfqq) {
 		cfqq = &cfqd->oom_cfqq;