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Tue, 07 Jul 2026 01:15:25 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:d4f4:6328:49c0:b912]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ccc9d1ecfesm7420045ad.47.2026.07.07.01.15.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 01:15:24 -0700 (PDT) Date: Tue, 7 Jul 2026 17:15:21 +0900 From: Sergey Senozhatsky To: Sebastian Andrzej Siewior Cc: Sergey Senozhatsky , Andrew Morton , Yosry Ahmed , Hillf Danton , Kairui Song , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v10 01/19] zram: sleepable entry locking Message-ID: References: <20250303022425.285971-1-senozhatsky@chromium.org> <20250303022425.285971-2-senozhatsky@chromium.org> <20260707064030.D843llKh@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260707064030.D843llKh@linutronix.de> On (26/07/07 08:40), Sebastian Andrzej Siewior wrote: [..] > > static void zram_slot_lock(struct zram *zram, u32 index) > > { > > - spin_lock(&zram->table[index].lock); > > + unsigned long *lock = &zram->table[index].flags; > > + > > + mutex_acquire(slot_dep_map(zram, index), 0, 0, _RET_IP_); > > + wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK, TASK_UNINTERRUPTIBLE); > > + lock_acquired(slot_dep_map(zram, index), _RET_IP_); > > } > > Looking at this, is there a special need to have a lockdep map per > table? Wouldn't it be enough to have one per zram? Logically you use the > same __key so I don't think it makes much of a difference but you could > lower the memory usage a bit by having less of those structs per zram. So the idea was to separate lockdep maps and keep them per-device because various zram devices can be on different IO paths with very different locking graphs. E.g. zram0 can be a swap device with all the locks that swap layer has, while zram1 can be a "normal" block device mounted with ext4 with all the locks that ext4/vfs bring.