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FAILED: patch "[PATCH] blk-cgroup: blk_cgroup_bio_start() should use irq-safe" failed to apply to 5.14-stable tree

PATCH [email protected] 1 participant 1 message Nov 13, 2021

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The patch below does not apply to the 5.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3c08b0931eedd04c530040499fadeccab50ed646 Mon Sep 17 00:00:00 2001
From: Tejun Heo <[email protected]>
Date: Thu, 14 Oct 2021 13:20:22 -1000
Subject: [PATCH] blk-cgroup: blk_cgroup_bio_start() should use irq-safe
operations on blkg->iostat_cpu

c3df5fb57fe8 ("cgroup: rstat: fix A-A deadlock on 32bit around u64_stats_sync") made u64_stats updates irq-safe to avoid A-A deadlocks. Unfortunately, the conversion missed one in blk_cgroup_bio_start(). Fix it.

Fixes 2d146aa3aa84 ("mm: memcontrol: switch to rstat")
Cc [email protected] # v5.13+
Reported-by [email protected]
Signed-off-by Tejun Heo <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Jens Axboe <[email protected]>
block/blk-cgroup.c +3 -2
index 38b9f7684952..9a1c5839dd46 100644
@@ -1897,10 +1897,11 @@ void blk_cgroup_bio_start(struct bio *bio)
 {
 	int rwd = blk_cgroup_io_type(bio), cpu;
 	struct blkg_iostat_set *bis;
+	unsigned long flags;
 
 	cpu = get_cpu();
 	bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
-	u64_stats_update_begin(&bis->sync);
+	flags = u64_stats_update_begin_irqsave(&bis->sync);
 
 	/*
 	 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split

@@ -1912,7 +1913,7 @@ void blk_cgroup_bio_start(struct bio *bio)
 	}
 	bis->cur.ios[rwd]++;
 
-	u64_stats_update_end(&bis->sync);
+	u64_stats_update_end_irqrestore(&bis->sync, flags);
 	if (cgroup_subsys_on_dfl(io_cgrp_subsys))
 		cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu);
 	put_cpu();