tcm_loop_target_reset() violates the SCSI EH contract: it returns SUCCESS
without draining any in-flight commands. The SCSI EH documentation
(scsi_eh.rst) requires that when a reset handler returns SUCCESS the driver
has made lower layers "forget about timed out scmds" and is ready for new
commands. Every other SCSI LLD (virtio_scsi, mpt3sas, ipr, scsi_debug,
mpi3mr) enforces this by draining or completing outstanding commands before
returning SUCCESS.
Because tcm_loop_target_reset() doesn't drain, the SCSI EH reuses in-flight
scsi_cmnd structures for recovery commands (e.g. TUR) while the target core
still has async completion work queued for the old se_cmd. The memset in
queuecommand zeroes se_lun and lun_ref_active, causing
transport_lun_remove_cmd() to skip its percpu_ref_put(). The leaked LUN
reference prevents transport_clear_lun_ref() from completing, hanging
configfs LUN unlink forever in D-state:
INFO: task rm:264 blocked for more than 122 seconds.
rm D 0 264 258 0x00004000
Call Trace:
__schedule+0x3d0/0x8e0
schedule+0x36/0xf0
transport_clear_lun_ref+0x78/0x90 [target_core_mod]
core_tpg_remove_lun+0x28/0xb0 [target_core_mod]
target_fabric_port_unlink+0x50/0x60 [target_core_mod]
configfs_unlink+0x156/0x1f0 [configfs]
vfs_unlink+0x109/0x290
do_unlinkat+0x1d5/0x2d0
Fix this by making tcm_loop_target_reset() actually drain commands:
1. Issue TMR_LUN_RESET via tcm_loop_issue_tmr() to drain all commands that
the target core knows about (those not yet CMD_T_COMPLETE).
2. Use blk_mq_tagset_busy_iter() to iterate all started requests and
flush_work() on each se_cmd — this drains any deferred completion work
for commands that already had CMD_T_COMPLETE set before the TMR (which
the TMR skips via __target_check_io_state()). This is the same pattern
used by mpi3mr, scsi_debug, and libsas to drain outstanding commands
during reset.
Fixes: e0eb5d38b7 ("scsi: target: tcm_loop: Use block cmd allocator for se_cmds")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://patch.msgid.link/27011aa34c8f6b1b94d2e3cf5655b6d037f53428.1773706803.git.josef@toxicpanda.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
1333eee56c