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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="THGcJ4Yz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37C51C433F1; Fri, 22 Mar 2024 22:24:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711146274; bh=u9hLQq6AbccTuvOfTFuQN65uvQDoNtfDPvG6xM7TeA4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=THGcJ4YzFy+bIbZ5yw6EferzhNPNLNAFaPtsewBMPNNW+5dyCef7pSpzLtVSH1KFQ NxIkOcDhIhDOck+jrsDOzlf0tO1vDyN1grFlvCVLZo5gaNR6U1F7YRF51w/1CQL9BC TYhaFcARm1WIhHQp1XgJEkdR/MwaQp/I++cR6O895VhE8YVxViT/bK0IOIX8ThpMVU LEwinwAeVZerafNzdxgTCP49aJca7dmC5vqNULFc3p5eI9IonrJh/WzVHckBvPsqrV TZlfvZRTornG7hn3WTCbEyRYjhlZZNxg0ePBqY8hd1wNMAyG/sKqUDClekThul1Q5k lw3revJJdR8KQ== Date: Fri, 22 Mar 2024 22:24:32 +0000 From: Jaegeuk Kim To: Light Hsieh =?utf-8?B?KOisneaYjueHiCk=?= Cc: Hillf Danton , "linux-kernel@vger.kernel.org" , "linux-f2fs-devel@lists.sourceforge.net" Subject: Re: =?utf-8?B?5Zue6KaGOiBbUEFUQ0g=?= =?utf-8?Q?=5D?= f2fs: avoid the deadlock case when stopping discard thread Message-ID: References: <20240320001442.497813-1-jaegeuk@kernel.org> <20240321224233.2541-1-hdanton@sina.com> 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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 03/22, Light Hsieh (謝明燈) wrote: > I don't see my added log in sb_free_unlock() which will invoke percpu_up_write to release the write semaphore. May I ask more details whether thaw_super() was called or not? > > > ________________________________ > 寄件者: Jaegeuk Kim > 寄件日期: 2024年3月22日 上午 08:29 > 收件者: Hillf Danton > 副本: linux-kernel@vger.kernel.org ; Light Hsieh (謝明燈) ; linux-f2fs-devel@lists.sourceforge.net > 主旨: Re: [PATCH] f2fs: avoid the deadlock case when stopping discard thread > > > External email : Please do not click links or open attachments until you have verified the sender or the content. > > On 03/22, Hillf Danton wrote: > > On Tue, 19 Mar 2024 17:14:42 -0700 Jaegeuk Kim > > > f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC) issue_discard_thread > > > - mnt_want_write_file() > > > - sb_start_write(SB_FREEZE_WRITE) > > __sb_start_write() > > percpu_down_read() > > > - sb_start_intwrite(SB_FREEZE_FS); > > __sb_start_write() > > percpu_down_read() > > > > Given lock acquirers for read on both sides, wtf deadlock are you fixing? > > Damn. I couldn't think _write uses _read sem. > > > > > > - f2fs_stop_checkpoint(sbi, false, : waiting > > > STOP_CP_REASON_SHUTDOWN); > > > - f2fs_stop_discard_thread(sbi); > > > - kthread_stop() > > > : waiting > > > > > > - mnt_drop_write_file(filp); > > > > More important, feel free to add in spin. > > I posted this patch before Light reported. > > And, in the report, I didn't get this: > > f2fs_ioc_shutdown() --> freeze_bdev() --> freeze_super() --> sb_wait_write(sb, SB_FREEZE_FS) --> ... ->percpu_down_write(). > > because f2fs_ioc_shutdown() calls f2fs_stop_discard_thread() after thaw_bdev() > like this order. > > -> freeze_bdev() > -> thaw_bdev() > -> f2fs_stop_discard_thread() > > Am I missing something? > > > > > Reported-by: "Light Hsieh (謝明燈)" >