linux-kernel - [PATCH for-6.18/block 1/2] blk-cgroup: allocate policy data with GFP_NOIO in blkcg_activate

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Message-Id: <20250923075520.3746244-2-yukuai1@huaweicloud.com>
Date: Tue, 23 Sep 2025 15:55:19 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: nilay@...ux.ibm.com,
	tj@...nel.org,
	josef@...icpanda.com,
	axboe@...nel.dk
Cc: cgroups@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH for-6.18/block 1/2] blk-cgroup: allocate policy data with GFP_NOIO in blkcg_activate_policy()

From: Yu Kuai <yukuai3@...wei.com>

Queue is freezed while activating policy, allocate memory with queue
freezed has the risk of deadlock because memory reclaim can issue new
IO.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-cgroup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 7246fc256315..0c7b58696d3c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1630,7 +1630,7 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
 		if (!pd) {
 			/*
 			 * GFP_NOWAIT failed.  Free the existing one and
-			 * prealloc for @blkg w/ GFP_KERNEL.
+			 * prealloc for @blkg w/ GFP_NOIO.
 			 */
 			if (pinned_blkg)
 				blkg_put(pinned_blkg);
@@ -1642,7 +1642,7 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
 			if (pd_prealloc)
 				pol->pd_free_fn(pd_prealloc);
 			pd_prealloc = pol->pd_alloc_fn(disk, blkg->blkcg,
-						       GFP_KERNEL);
+						       GFP_NOIO);
 			if (pd_prealloc)
 				goto retry;
 			else
-- 
2.39.2