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(dynamic-176-007-212-220.176.7.pool.telefonica.de. [176.7.212.220]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488fb7b2716sm209489945e9.30.2026.04.25.07.29.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Apr 2026 07:29:39 -0700 (PDT) From: Abd-Alrhman Masalkhi To: song@kernel.org, yukuai@fnnas.com Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC] md/raid1: possible deadlock introduced in raid1_read_request() Date: Sat, 25 Apr 2026 16:29:38 +0200 Message-ID: <20260425142938.5555-1-abd.masalkhi@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit hi, The raid1_read_request() function splits a bio regardless of whether it is an original bio or an md-cloned bio (regardless of the r1bio_existed value). When an md_cloned_bio is resubmitted, raid1_read_request() treats it as a new original bio instead of recognizing it as an md_cloned_bio. If I understand this correctly, this results in allocating a new r1bio, etc. More importantly, this may lead to a deadlock if we tried to suspended the array before the md driver calls percpu_ref_tryget_live() (&mddev->active_io) on the path down to pers->make_request(). I am considering two possible approaches, ending the bio if max_sectors is smaller than bio_sectors(bio), or modifing read_balance() to select a disk that can handle the full bio if r1bio_existed was set. Is this understanding correct? and What might be the preferred approach in this case? Thanks, Abd-Alrhman