libnvme - cpp-dump: crash due to missing transport handle

[dwsuse]

The cpp-dump test crashes on older kernels where the fance 'csi', 'nuse' and 'metadata_bytes' sys entries are missing. In this case a nvme_ns_identify is used:

(gdb) bt
#0  0x00007ffff7f9208c in nvme_submit_admin_passthru (hdl=0x0, cmd=0x7fffffffd6a0) at ../libnvme/src/nvme/ioctl.c:189
#1  0x00007ffff7fa4d29 in nvme_ns_identify (n=0x416b80, ns=0x417000) at ../libnvme/src/nvme/tree.c:2422
#2  0x00007ffff7fa5837 in nvme_ns_init (path=0x416490 "/sys/class/nvme/nvme0/nvme0n1", ns=0x416b80) at ../libnvme/src/nvme/tree.c:2691
#3  0x00007ffff7fa5b60 in nvme_ns_open (ctx=0x4162b0, sys_path=0x416490 "/sys/class/nvme/nvme0/nvme0n1", name=0x416740 "nvme0n1", ns=0x7fffffffda30) at ../libnvme/src/nvme/tree.c:2763
#4  0x00007ffff7fa5d86 in __nvme_scan_namespace (ctx=0x4162b0, sysfs_dir=0x4169a0 "/sys/class/nvme/nvme0", name=0x4164d3 "nvme0n1", ns=0x7fffffffda80) at ../libnvme/src/nvme/tree.c:2823
#5  0x00007ffff7fa6198 in nvme_ctrl_scan_namespace (ctx=0x4162b0, c=0x416760, name=0x4164d3 "nvme0n1") at ../libnvme/src/nvme/tree.c:2917
#6  0x00007ffff7fa32ca in nvme_ctrl_scan_namespaces (ctx=0x4162b0, c=0x416760) at ../libnvme/src/nvme/tree.c:1875
#7  0x00007ffff7fa48d4 in nvme_scan_ctrl (ctx=0x4162b0, name=0x41e683 "nvme0", cp=0x7fffffffdb98) at ../libnvme/src/nvme/tree.c:2271
#8  0x00007ffff7f9f8aa in nvme_scan_topology (ctx=0x4162b0, f=0x0, f_args=0x0) at ../libnvme/src/nvme/tree.c:293
#9  0x00007ffff7f9fb27 in nvme_scan (config_file=0x0, ctxp=0x7fffffffdc10) at ../libnvme/src/nvme/tree.c:357
#10 0x00000000004011b1 in main () at ../libnvme/test/cpp.cc:22

[igaw]

If the tests are run as normal user, it's not possible to open nvme0n1 (or do IOCTLs). In the above case nvme_ns_init tries to access the device to do a nvme identify command. With the proper error propagation in place, this error is detected.

With libnvme 1.x it's just ignored and papered over:

$ .build/test/test-cpp
Failed to open ns nvme0n1, errno 13
nvme-subsys0 - NQN=nqn.2021-03.com.kingston:nvme:nvm-subsystem-sn-50026B768623DB3D
 - nvme0 pcie 0000:01:00.0 live

$ strace .build/test/test-cpp
[...]
openat(AT_FDCWD, "/dev/nvme0n1", O_RDONLY) = -1 EACCES (Permission denied)
write(2, "Failed to open ns nvme0n1, errno"..., 36Failed to open ns nvme0n1, errno 13) = 36
ioctl(-1, NVME_IOCTL_ADMIN_CMD, 0x7fff6c8b8c80) = -1 EBADF (Bad file descriptor)
[...]