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Thu, 27 Nov 2025 07:04:30 -0800 (PST) X-Google-Smtp-Source: AGHT+IH0q+jG9hC7aC3Vz7k6tpz1VUndT7UiQuyQKmRF7Lbe9RLuTVjni63W2NQvWhkUuYV04UAaAg== X-Received: by 2002:ac8:7d85:0:b0:4ee:1576:a75b with SMTP id d75a77b69052e-4ee58afa229mr321569111cf.78.1764255870386; Thu, 27 Nov 2025 07:04:30 -0800 (PST) Received: from x1.local ([142.188.210.156]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4efd34324f9sm9629891cf.24.2025.11.27.07.04.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Nov 2025 07:04:29 -0800 (PST) Date: Thu, 27 Nov 2025 10:04:27 -0500 From: Peter Xu To: =?utf-8?B?UGF3ZcWCIFptYXJ6xYJ5?= Cc: qemu-devel@nongnu.org, farosas@suse.de Subject: Re: [PATCH] migration: Fix writing mapped_ram + ignore_shared snapshots Message-ID: References: <20251126154734.940066-1-pzmarzly0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.224, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Nov 27, 2025 at 11:35:06AM +0000, Paweł Zmarzły wrote: > On Wed, 26 Nov 2025 at 21:42, Peter Xu wrote: > > Now I start to question whether I should have that other fix of yours to be > > for this release or next. > > > > If this use case is completely broken, we shouldn't need to rush -rc > > window, now I plan to merge all these fixes later when 11.0 dev window > > opens. Let me know if you, or Fabiano, has any comments. > > It is broken if you set ignore-shared and actually have any shared > block, but what could work today is if you just toggle the > ignore-shared flag on without setting up any shared blocks. In that > case, writing will work fine, but reading will crash. That's how I Yep, I suppose either side of reliable failure means it's completely broken. :( That's IMHO an important evaluation because we could modify the image layout without worrying breaking others only if it's completely broken.. > stumbled upon this rabbithole in the first place: I forgot to unset > the flag and was surprised by parsing error. Whether it is worth > fixing now - I don't know, setting ignore-shared when there are no > shared blocks doesn't really make sense, so most likely nobody does it > on purpose. > > In either case, I need to stop working on this for now, I thought this > will be a tiny side project that'll help me get my first patches in > (and get used to collaborating over email), but now it's growing in > complexity and I have other things that I need to prioritize. > Hopefully I'll come back to this within 11.x window. Thanks for all > the help so far, Peter, Fabiano! Don't worry, thanks for all the contributions even so far! Your patch actually looks pretty good already and mergeable, I just nitpicked things here and there as I want to double check on things I stated, and make it slow to get thoroughly discussed. Personally, I think it's ok we queue this one already into -next together with the other one, then we clean things on top. Fabiano, sounds good to you? PS: take your time reading, as long as you agree we put it in -next only, then there's no rush. :) Thanks, -- Peter Xu