>> If LLD has added scsi device (by calling scsi_add_device) before >> scheduling async scsi_scan_host then scsi_finish_async_scan() will end >> up calling scsi_sysfs_add_sdev for scsi device which was already added by LLD. >> This patch fixes this issue by adding a check at the start of >> scsi_sysfs_add_sdev() to skip the device add if it's already visible >> to rest of the kernel. > > This looks wrong to me. I guess this happens for the case where you > added the well known lun explicitly, and then have one of the devices that also report it from REPORT LUNS? I guess the right answer is to explicitly ignore wluns in scsi_report_lun_scan. No, It happens in this sequence of events: 1. LLD calls the __scsi_add_device() for well known logical units before scsi_scan_host() (This is done as part of [PATCH V5 10/17] scsi: ufs: manually add well known logical units). __scsi_add_device() will also add the scsi device to sysfs by calling scsi_sysfs_add_sdev() 2. Now LDD calls the scsi_scan_host() (Note that CONFIG_SCSI_SCAN_ASYNC is enabled) which will schedule the async scan. Device reports only normal LUs (no w-lus reported here) when REPORT LUNs in sent with SELECT REPORT cleared. At the end of async scan, scsi_finish_async_scan() calls scsi_sysfs_add_devices(). scsi_sysfs_add_devices() iterates through all the scsi_device instances attached to Scsi_Host hence end up calling scsi_sysfs_add_sdev() 2nd time for the scsi_device which were already added explicitly by LDD. BTW, none of the UFS devices are reporting the W-LUs when SELECT REPORT is cleared. I was confused with the crash (which is fixed by this patch) seen with scenario mentioned above and thought that REPORT LUNs (with SELECT REPORT=00h) is reporting W-LUs as well but I confirmed that that's not the case with any of the UFS device vendors. -----Original Message----- From: linux-scsi-owner@xxxxxxxxxxxxxxx [mailto:linux-scsi-owner@xxxxxxxxxxxxxxx] On Behalf Of Christoph Hellwig Sent: Wednesday, September 24, 2014 9:08 AM To: Dolev Raviv Cc: James.Bottomley@xxxxxxxxxxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; linux-scsi-owner@xxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; santoshsy@xxxxxxxxx; Subhash Jadavani Subject: Re: [PATCH V5 02/17] scsi: sysfs: don't add scsi_device if its already added On Wed, Sep 24, 2014 at 06:13:58PM +0300, Dolev Raviv wrote: > From: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx> > > If LLD has added scsi device (by calling scsi_add_device) before > scheduling async scsi_scan_host then scsi_finish_async_scan() will end > up calling scsi_sysfs_add_sdev for scsi device which was already added by LLD. > This patch fixes this issue by adding a check at the start of > scsi_sysfs_add_sdev() to skip the device add if it's already visible > to rest of the kernel. This looks wrong to me. I guess this happens for the case where you added the well known lun explicitly, and then have one of the devices that also report it from REPORT LUNS? I guess the right answer is to explicitly ignore wluns in scsi_report_lun_scan. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
