Merge branch 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fix from Tejun Heo:
 "One commit to fix a possible A-A deadlock around u64_stats_sync on
  32bit machines caused by updating it without disabling IRQ when it may
  be read from IRQ context"

* 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: rstat: fix A-A deadlock on 32bit around u64_stats_sync

1 files changed, 8 insertions, 6 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 575d7a2e7203..31fe9be179d9 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -790,6 +790,7 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 		struct blkcg_gq *parent = blkg->parent;
 		struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu);
 		struct blkg_iostat cur, delta;
+		unsigned long flags;
 		unsigned int seq;
 
 		/* fetch the current per-cpu values */
@@ -799,21 +800,21 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 		} while (u64_stats_fetch_retry(&bisc->sync, seq));
 
 		/* propagate percpu delta to global */
-		u64_stats_update_begin(&blkg->iostat.sync);
+		flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
 		blkg_iostat_set(&delta, &cur);
 		blkg_iostat_sub(&delta, &bisc->last);
 		blkg_iostat_add(&blkg->iostat.cur, &delta);
 		blkg_iostat_add(&bisc->last, &delta);
-		u64_stats_update_end(&blkg->iostat.sync);
+		u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
 
 		/* propagate global delta to parent (unless that's root) */
 		if (parent && parent->parent) {
-			u64_stats_update_begin(&parent->iostat.sync);
+			flags = u64_stats_update_begin_irqsave(&parent->iostat.sync);
 			blkg_iostat_set(&delta, &blkg->iostat.cur);
 			blkg_iostat_sub(&delta, &blkg->iostat.last);
 			blkg_iostat_add(&parent->iostat.cur, &delta);
 			blkg_iostat_add(&blkg->iostat.last, &delta);
-			u64_stats_update_end(&parent->iostat.sync);
+			u64_stats_update_end_irqrestore(&parent->iostat.sync, flags);
 		}
 	}
 
@@ -848,6 +849,7 @@ static void blkcg_fill_root_iostats(void)
 		memset(&tmp, 0, sizeof(tmp));
 		for_each_possible_cpu(cpu) {
 			struct disk_stats *cpu_dkstats;
+			unsigned long flags;
 
 			cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
 			tmp.ios[BLKG_IOSTAT_READ] +=
@@ -864,9 +866,9 @@ static void blkcg_fill_root_iostats(void)
 			tmp.bytes[BLKG_IOSTAT_DISCARD] +=
 				cpu_dkstats->sectors[STAT_DISCARD] << 9;
 
-			u64_stats_update_begin(&blkg->iostat.sync);
+			flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
 			blkg_iostat_set(&blkg->iostat.cur, &tmp);
-			u64_stats_update_end(&blkg->iostat.sync);
+			u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
 		}
 	}
 }