Public bug reported: SRU Justification
[Impact] The linux-azure-cvm kernel (e.g. Ubuntu-azure-cvm-5.4.0-1078.81+cvm1) has a race condition bug in the Linux vmbus bounce buffer code (drivers/hv/hv_bounce.c), and as a result somtimes the kenrel fails to detect some of the SCSI disks, and the Linux dmesg log may show one of the 2 messages: #1: [ 2.995732] sd 3:0:0:3: [sdd] Sector size 0 reported, assuming 512. #2: [ 3.651293] scsi host3: scsi scan: INQUIRY result too short (5), using 36 Sometimes I see a strange call-trace (the 'order's is 18, if I print it) 2022-04-26T20:10:18,398144+00:00 kmalloc_order_trace+0x1e/0x80 2022-04-26T20:10:18,398147+00:00 __kmalloc+0x3ae/0x4c0 2022-04-26T20:10:18,398150+00:00 __scsi_scan_target+0x283/0x590 2022-04-26T20:10:18,398155+00:00 scsi_scan_channel.part.16+0x62/0x80 2022-04-26T20:10:18,398158+00:00 scsi_scan_host_selected+0xd5/0x150 2022-04-26T20:10:18,398160+00:00 store_scan+0xc8/0xe0 (This is very strange because 'order 18' means (1 << 18) * 4096 bytes = 1GBytes.) After some investigation, we eventually got the root cause and made a fix: https://github.com/dcui/linux-azure-cvm/commit/ddde4dc33242794000e1d9667a5f9cfa31c15fdf With the fix, we no longer see the above strange symptoms. Please include the fix into the next release of the v5.4 linux-azure-cvm kernel. Thanks! [Test case] Microsoft tested [Where things could go wrong] Some SCSI drives may continue to go undetected. [Other Info] SF: #00335631 ** Affects: linux-azure-cvm (Ubuntu) Importance: Medium Assignee: Tim Gardner (timg-tpi) Status: In Progress ** Package changed: linux (Ubuntu) => linux-azure-cvm (Ubuntu) ** Changed in: linux-azure-cvm (Ubuntu) Importance: Undecided => Medium ** Changed in: linux-azure-cvm (Ubuntu) Status: New => In Progress ** Changed in: linux-azure-cvm (Ubuntu) Assignee: (unassigned) => Tim Gardner (timg-tpi) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1971164 Title: [Azure][CVM] hv/bounce buffer: Fix a race that can fail disk detection To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-azure-cvm/+bug/1971164/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
