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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="i0DTX3Of" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B63ACC433C7; Tue, 26 Mar 2024 16:52:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711471925; bh=VGvzPDcwbNrB7wKDzQn4uUId9Ig5vPtwkz+8ZQqrXYk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=i0DTX3OfeIm6YD6OdHw6XMb8uCR9Z76AcPa8PWbQnad9qf6RLepfxF5YX3K7SAAdp VKZ2d8+V8DBmfmlItdFCTflf0a8NYFgs3S8RAC5KvB11pQu6aue3IWw9v7pHGUFWgh 5ggMKUhHt7sdv1j3FgdmPpfdVqlrtnpFk9egkskBzHkJoaT2zsMkICjzSe0czmW4k5 EMGJCFKKg6KeDtAlw6ejWsCyDbLDkML0y0gLc0THsloZKj65kMw8h6DgDyuBo8Fxv3 tRbb/xR9unKwIEfyHn8lzHIjvQoexEDLMyTpGY9AILPOz+PHBWqdD0WmxxQKu1KbDN oeu/NE0C0lh9Q== Date: Tue, 26 Mar 2024 16:52:04 +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, Jaegeuk Kim wrote: > 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? Ping? > > > > > > > ________________________________ > > 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)" > >