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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6a0fc62sm38411395ad.40.2024.07.10.15.12.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jul 2024 15:12:29 -0700 (PDT) Sender: Tejun Heo Date: Wed, 10 Jul 2024 12:12:28 -1000 From: Tejun Heo To: "boy.wu" Cc: Josef Bacik , Jens Axboe , Matthias Brugger , AngeloGioacchino Del Regno , Boris Burkov , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, iverlin.wang@mediatek.com Subject: Re: [PATCH v2] blk-cgroup: Replace u64_sync with blkg_stat_lock for stats update Message-ID: References: <20240710061334.1888-1-boy.wu@mediatek.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240710061334.1888-1-boy.wu@mediatek.com> Hello, On Wed, Jul 10, 2024 at 02:13:34PM +0800, boy.wu wrote: ... > @@ -952,7 +952,6 @@ static void blkcg_fill_root_iostats(void) > struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg; > struct blkg_iostat tmp; > int cpu; > - unsigned long flags; > > memset(&tmp, 0, sizeof(tmp)); > for_each_possible_cpu(cpu) { > @@ -974,9 +973,10 @@ static void blkcg_fill_root_iostats(void) > cpu_dkstats->sectors[STAT_DISCARD] << 9; > } > > - flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); > +#if BITS_PER_LONG == 32 > + guard(raw_spinlock_irqsave)(&blkg_stat_lock); > +#endif > blkg_iostat_set(&blkg->iostat.cur, &tmp); > - u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags); Isn't the problem shared across other blkg->iostat.sync users too? Also, maybe, we can just grab the spinlock without testing for 32bit. blkg->iostat (unlike the per-cpu counterpart) isn't accessed that frequently, so keeping it simple and consistent probably makes more sense, right? Thanks. -- tejun