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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-48e71bc615asi30760718f8f.337.2026.11.03.02.11.07 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 02:11:07 -0800 (PST) Received-SPF: pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=NdOsYIkK; spf=pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=khorenko@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Message-Id:Date:From:Subject:Content-Type: MIME-Version; bh=7AyqZdllfIi0SEgfQnea9fy+xu2OhccmFWoiTt4/ZLU=; b=NdOsYIkKwK4l Lc97RHGcCkDkHX15ke7tEiyjEGFCic6kjh2R7PSpuzMufTxsWYYsBeuwKvtD3QjxNyYWRsOe4AaGI ZYW4oPv/7vPn2t/3KbxAu+WxrY87CekSjHGra0XEdanxevkrNbkaRbn+5fy8hOPIcJfUJ05zZTu8x XBUa2RDI8aEsTQtcRIwEmwiKhY9gxiHXoFZ77WK5YmQQh2xh2bnvJ54DIpIdLD1YvaLxNvKVY8mF0 YWV3zVs0Qx/DgONX8hIel3LmrjSLzobXa0hlD1vCAV46z4z2VZqTtIKpUefhHhiAfPjHIMyy2Z8Pq l7Ul51BOj+4TB5c/3qgPZw==; Received: from ch-demo-asa.virtuozzo.com ([130.117.225.8] helo=f0.sw.ru) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1xOBQ0-00BKVK-16; Tue, 03 Nov 2026 11:10:57 +0100 MIME-Version: 1.0 From: Konstantin Khorenko To: Andrey Zhadchenko In-Reply-To: <20261103080358.723186-1-andrey.zhadchenko@virtuozzo.com> References: <20261103080358.723186-1-andrey.zhadchenko@virtuozzo.com> Date: Tue, 03 Nov 2026 11:11:03 +0100 Message-Id: <179370066311.2382033.9670419479778917565.b4-review@b4> X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2195; i=khorenko@virtuozzo.com; h=from:subject:message-id; bh=GfLJBU6xxWgwdiPvfg1gID9BlrmloST1Ebb3krn+M2A=; b=owEBbQKS/ZANAwAKAVGWCkf5YVwqAcsmYgBq6bM4ZyZcqcEm626sOEE5wGt0lfcPh84h1KcaW Pw5UWePNHCJAjMEAAEKAB0WIQRWD23IPcXT0GO9CCxRlgpH+WFcKgUCaumzOAAKCRBRlgpH+WFc KlcpEACcXh6UClw2eRKxaGr2kSjauaDL484iEXXArvIUZsuym6eFUNyMa1Ekx1SFVpeiYXYFNT3 QVuSgrh/vX3k4w3f3OeFPf8GeJHjTdXxqAPldbKNpauGaGN1jXPOao5QCYr76LDTD0txPHstaAQ teMpf5mRuZd4YGYOXqJPOFoy2QimBtYBqTCV6kGHRoLGTZcd1ZoM0YeNOcvzyoxRTM87pj0gUKT vmbTD9Q+/kMTpExKpv2aG/zrJBXlg8uB4Z5/TZaa+tlS+9V48FDRfw7Yyrrxo1/97lIWvGBc/9O bi++SSpJLSItPUYbi1MWzXq8KV3s+Kxf5BYyvz2Tb47qKVI13xPLZA5EGCyziLmRcQ2NbaNrPDM 7bsFzPqwUhb6NpfK+lkQkeCJ4HWltxYuY74onozL7fUzFsH3hN3oM/XNryuauNWDU7QVc2Ml3ES sw0GL7uORSkFKVcKZPu1hwLJi1kjr3+TUJiZD2bSOReWtAaaJLYqh+8SNtMlJsdnbYrPCw0NAdw LeUzoi8KPiHo+C9CbKWtj8oEL7xv4qeP9wMd/ljl8TrXvk8ZvD54BCLZAcP0FIeoqSqOnlsspVJ x3x0XZ/GLKb/sRBXFLXysnye2mn2c8OuKZCRHNua7lhKtrBhqkdDBZ2IQ+tqx5Ur+HFyXrmEwle gAe67Od/1yu3Deg== X-Developer-Key: i=khorenko@virtuozzo.com; a=openpgp; fpr=560F6DC83DC5D3D063BD082C51960A47F9615C2A X-OZ-Fwd: true Cc: devel@openvz.org Subject: Re: [Devel] [PATCH hci-8.1 v4 0/6] dm/push_backup: event fd interface and fixes X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org On 11/3/26 11:03, Andrey Zhadchenko wrote: > Patches 1-5 are fixes found while working on this: Hi Andrey, Thanks, the direction is right and the fd interface itself holds up. Remarks are inline in the patches, the main ones: - 5/6: the !pb->alive bail-out in pb_timer_func() can leave guest writes delayed for good after an interrupted "push_backup_stop". Checking pb->nr_delayed instead keeps everything the patch needs. - 3/6 opens a window that only 5/6 closes, so please put 5/6 first or fold 3/6 into it. - 6/6: the fd is not bound to a backup session; please decide this before the UAPI is fixed. - pb_ctr() returns 0 with a freed pb when alloc_ordered_workqueue() fails. It is older than the series, but 1/6 is about exactly these error paths. Series-wide: - Every vz commit needs a "Feature:" line. The earlier dm-push-backup commits carry "Feature: dm-backup: push backup target driver". - The subject prefix of the driver history and of this cover letter is "dm/push_backup:", the patches use "drivers/md/push_backup:". The 3/6 subject is 75 characters. > 3. drop the redundant mod_timer() in push_backup_write(). The timer > re-arms itself from pb->deadline_jiffies, so updating the deadline > under the lock is enough. This was also the only place that armed > the timer outside the window push_backup_stop() waits for, which > matters once writes may arrive via the fd without pb->ctl_rwsem; Same as in 3/6: pb_timer_func() also re-arms outside that window, so "the only place" does not hold. > 4. pass absolute expiry to mod_timer(). Both remaining callers passed > a relative value, so after ~5 min of uptime the timer fired and > re-armed on every tick while a write was delayed; On 64-bit this happens from boot, not after 5 minutes, see 4/6. > 5. arm the timer under pb->lock and wait for its callback properly. This item is accurate and is the description 5/6 itself should carry. It is one paragraph of six sentences though; splitting it into the race, the stop race and the RCU removal would read easier. -- Konstantin Khorenko, Virtuozzo Linux Kernel Team _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel