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Sat, 22 Nov 2025 16:08:31 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:296e:57d:751e:5598]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7c3ecf7d70asm10039686b3a.13.2025.11.22.16.08.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 22 Nov 2025 16:08:31 -0800 (PST) Date: Sun, 23 Nov 2025 09:08:25 +0900 From: Sergey Senozhatsky To: Gao Xiang Cc: Sergey Senozhatsky , Yuwen Chen , akpm@linux-foundation.org, bgeffon@google.com, licayy@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, richardycc@google.com Subject: Re: [RFC PATCHv5 0/6] zram: introduce writeback bio batching Message-ID: References: <8c596737-95c1-4274-9834-1fe06558b431@linux.alibaba.com> <853796e3-fd44-4fc2-8fd2-5810342a6ebe@linux.alibaba.com> <2c6906d1-132e-401f-830f-ae771fe836c5@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c6906d1-132e-401f-830f-ae771fe836c5@linux.alibaba.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C3276140002 X-Stat-Signature: jxnry3br6egyijz86trnkajz1xktrw3r X-Rspam-User: X-HE-Tag: 1763856512-804410 X-HE-Meta: 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 M4ZJci2h X3ThOKOV9OhnyRgwfuvopfIn84sdQa8UIG5dmSu1ucVmc2h/06So7WKE3Mozv/jXSM+mMNhE5XUiwcdlhNWPEZjPyAb1ikh5XxyhS4kbevuU4uehltjTKgQ83aqTy27v4KvdGnmsRJqyOY1Gumm3vjox2LRHxJd078IcO05f5THwbDsW0zsrXZoMGQRC7OA7O5WSOYWDSYZ3RvilTJ+fj6Ew29xITxqmrm1TCc9rUDEPzNoKD8pYDwliNA5Wv8BhicddlGX8cn/QI+A/Ol2cnvEb4MlRuH78pJdaD7BDHw1x+Wcl0rR+ptneseDT0cIj2ur09hX3+rKRXLVZtpjOpPtdB3GkJNjSWa+gCNJ23aq0yWXOmXoxtAgai3YDHZzlU5Yomtetd/Zk3jxo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (25/11/22 22:09), Gao Xiang wrote: > > I thought you were talking about the backing device being > > ext4/btrfs. Sorry, I don't have enough context/knowledge > > to understand what you're getting at. zram has been doing > > writeback for ages, I really don't know what you mean by > > "to act like this". > > I mean, if zram is formatted as ext4, and then mount it; > and then there is a backing file which is also in another > ext4, you'd need a workqueue to do writeback I/Os (or needs > a loop device to transit), was that the original question > raised by Yuwen? We take pages of data from zram0 and write them straight to the backing device. Those writes don't go through vfs/fs so fs on the backing device will simply be corrupted, as far as I can tell. This is not intendant use case for zram writeback.