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[95.91.252.233]) by smtp.googlemail.com with ESMTPSA id cb4sm4820273ejb.82.2020.12.22.14.11.43 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 22 Dec 2020 14:11:44 -0800 (PST) Message-ID: <28211d08700d1e4876a9aea342e8fcb79534cd2c.camel@gmail.com> Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB on/off From: Bean Huo To: Can Guo , Stanley Chu Cc: alim.akhtar@samsung.com, avri.altman@wdc.com, asutoshd@codeaurora.org, jejb@linux.ibm.com, martin.petersen@oracle.com, beanhuo@micron.com, bvanassche@acm.org, tomas.winkler@intel.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 22 Dec 2020 23:11:43 +0100 In-Reply-To: References: <20201215230519.15158-1-huobean@gmail.com> <20201215230519.15158-2-huobean@gmail.com> <1608617307.14045.3.camel@mtkswgap22> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Tue, 2020-12-22 at 21:57 +0100, Bean Huo wrote: > > > May this operation race with UFS shutdown flow? > > > > > > To be more clear, ufshcd_wb_ctrl() here may be executed after > > > host > > > clock > > > is disabled by shutdown flow? > > > > > > If yes, we need to avoid it. > > > > I have the same doubt - can user still access sysfs nodes after > > system > > starts to run shutdown routines? If yes, then we need to remove all > > UFS > > sysfs nodes in ufshcd_shutdown(). > > > > No, we shouldn't do in this way, user space complains this. I think > the nodes in the sysfs can be shileded write, but the nodes shouldn't > be flash of its presence frequently. > > Thanks, > Bean > > > > Thanks, > > > > Can Guo. Hi Can Got your point, you don't want user space to interrupt UFS by sysyfs if UFS is in power down mode. if this is true, insteading of removing all sysfs node in ufshcd_shutdown, maybe just add this checkup before accessing UFS device descriptors/flag/attributes/LU: for example, for the device descriptor: diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs- sysfs.c index b3bf7fca00e5..881fe1c24a9f 100644 --- a/drivers/scsi/ufs/ufs-sysfs.c +++ b/drivers/scsi/ufs/ufs-sysfs.c @@ -262,6 +262,9 @@ static ssize_t ufs_sysfs_read_desc_param(struct ufs_hba *hba, u8 desc_buf[8] = {0}; int ret; + if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba)) + return -EACCES; + Bean