>From bugzilla. Reported against PCI, but I think the SCSI host number is determined by SCSI, not by PCI, so I don't see a PCI issue here. ---------- Forwarded message --------- From: <bugzilla-daemon@xxxxxxxxxx> Date: Thu, Jun 2, 2022 at 1:53 AM Subject: [Bug 216059] New: Scsi host number of Adaptec RAID controller changes upon a PCIe hotplug and re-insert To: <bjorn@xxxxxxxxxxx> https://bugzilla.kernel.org/show_bug.cgi?id=216059 Bug ID: 216059 Summary: Scsi host number of Adaptec RAID controller changes upon a PCIe hotplug and re-insert Product: Drivers Version: 2.5 Kernel Version: 4.18.11 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: PCI Assignee: drivers_pci@xxxxxxxxxxxxxxxxxxxx Reporter: sagar.biradar@xxxxxxxxxxxxx Regression: No Created attachment 301088 --> https://bugzilla.kernel.org/attachment.cgi?id=301088&action=edit The attachments contain the log files which capture before and after cases for a hotplug host number change Summary: This issue talks of the smartpqi driver for Adaptec controller, PCIe hotplug and the corresponding SCSI host number The Linux message log shows the host number (e.g. [14:2:0:0] storage - /dev/sg27) unexpectedly changing when PCIe hot remove is rapidly followed by PCIe hot add. The problem appears when the two PCIe events occur in quick succession (i.e. less than 2 minutes). Because of the timing factor, the issue can appear to be intermittent. The problem has been root caused as a kernel issue. Investigation: Kernel (4.18.11-hotplug-patch) debug prints were added in the “scsi_add_host( )” and “scsi_remove_host ( )” routines. Per the debug prints in the log, the scsi host number is released after the PCIe hot add event, which forces the kernel use a different host number. (debug prints) Line 48: [ 1811.461055] smartpqi 0000:b3:00.0: Debuggg . . . pqi_unregister_scsi function, before scsi_remove_host, shost->host_num=14 //smartpqi requests host num 14 to be removed Line 83: [ 2012.125750] (null): Debuggg . . shost->host_no before dev_set_name = host15 Line 84: [ 2012.126709] smartpqi 0000:b3:00.0: Debuggg . . . before scsi_add_host, shost->host_num=15 //upon hot add, kernel allocates host number 15, it should be 14 Line 132: [ 2014.181784] scsi host14: Debuggg . . in scsi_host_dev_release function shost_host_no to be removed = 14 //kernel finally frees host number 14, but it’s too late Conclusion: The kernel is not releasing the host number immediately when the smartpqi driver calls the scsi_remove_host() routine. If the PCIe cable is added back within 2 minutes, the kernel can unexpectedly return a different host number. This can lead to applications accessing the wrong device. This is a Linux kernel issue and we will be raising a bugzilla on the linux kernel. Questions: Will this be a problem for Amazon? (Wouldn’t they take several minutes to do this, they have to be very careful when hot plugging?) Do we need to consider other customers that might use PCIe hot plug in the future? The problem is observed in kernel V4.18.11, but would V5.04/V5.10 make a difference (should we test it ourselves)? Consequence: Application accesses wrong device. Rebooting system may still result in wrong host number. -- You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.
