blkcg, cfq-iosched: use GFP_NOWAIT instead of GFP_ATOMIC for non-crit…

…ical allocations blkcg performs several allocations to track IOs per cgroup and enforce resource control. Most of these allocations are performed lazily on demand in the IO path and thus can't involve reclaim path. Currently, these allocations use GFP_ATOMIC; however, blkcg can gracefully deal with occassional failures of these allocations by punting IOs to the root cgroup and there's no reason to reach into the emergency reserve. This patch replaces GFP_ATOMIC with GFP_NOWAIT for the following allocations. * bdi_writeback_congested and blkcg_gq allocations in blkg_create(). * radix tree node allocations for blkcg->blkg_tree. * cfq_queue allocation on ioprio changes. Signed-off-by: Tejun Heo <[email protected]> Suggested-and-Reviewed-by: Jeff Moyer <[email protected]> Suggested-by: Vivek Goyal <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
maraz · Aug 18, 2015 · d93a11f · d93a11f
1 parent 563180a
commit d93a11f
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Showing 2 changed files with 5 additions and 5 deletions.
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
@@ -188,7 +188,7 @@ EXPORT_SYMBOL_GPL(blkg_lookup);
 
 /*
  * If @new_blkg is %NULL, this function tries to allocate a new one as
- * necessary using %GFP_ATOMIC.  @new_blkg is always consumed on return.
+ * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.
  */
 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 				    struct request_queue *q,
@@ -208,15 +208,15 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	}
 
 	wb_congested = wb_congested_get_create(&q->backing_dev_info,
-					       blkcg->css.id, GFP_ATOMIC);
+					       blkcg->css.id, GFP_NOWAIT);
 	if (!wb_congested) {
 		ret = -ENOMEM;
 		goto err_put_css;
 	}
 
 	/* allocate */
 	if (!new_blkg) {
-		new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
+		new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT);
 		if (unlikely(!new_blkg)) {
 			ret = -ENOMEM;
 			goto err_put_congested;
@@ -882,7 +882,7 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
 done:
 	spin_lock_init(&blkcg->lock);
-	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
+	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
 #ifdef CONFIG_CGROUP_WRITEBACK
 	INIT_LIST_HEAD(&blkcg->cgwb_list);

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
@@ -3575,7 +3575,7 @@ static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
 	cfqq = cic_to_cfqq(cic, false);
 	if (cfqq) {
 		cfq_put_queue(cfqq);
-		cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio, GFP_ATOMIC);
+		cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio, GFP_NOWAIT);
 		cic_set_cfqq(cic, cfqq, false);
 	}