[PATCH v2 0/3] usb: uas / scsi: fail inflight and queued commands on dead links

[Sarthak Kukreti <sarthakkukreti@google.com>]

Unplugging a UAS device during system suspend after hub_wq is frozen
defers usb_disconnect() until hub_wq thaws. When sd_suspend_system()
issues SYNCHRONIZE_CACHE to the disconnected target:

1. If the HCD accepts the URBs, the status URB fails in uas_stat_cmplt()
   without completing the command, stranding SYNCHRONIZE_CACHE for the
   60s SCSI timeout and triggering the 25s DPM watchdog. Patch 1 tracks
   the active sense_urb per command and completes the owning command in
   uas_stat_cmplt() on status URB failure while unlinking any inflight
   data URBs.
2. If usb_submit_urb() fails with -ESHUTDOWN, -ENOENT, or -EHOSTUNREACH,
   uas_queuecommand_lck() requeues the command instead of failing it,
   and leaks unsubmitted URBs or orphans already-submitted URBs on
   partial submission failure. Patch 2 fails the command with
   DID_NO_CONNECT, frees unsubmitted URBs, and unlinks any submitted
   status or data URBs.
3. When the command completes with DID_NO_CONNECT,
   scsi_check_passthrough() matches SCMD_FAILURE_RESULT_ANY and retries
   it against the disconnected target. Patch 3 skips retries on
   DID_NO_CONNECT, DID_BAD_TARGET, and DID_TRANSPORT_FAILFAST.

Tested using a USB/IP (vhci_hcd) UAS target emulator that freezes
hub_wq, injects -EPROTO on the status URB during inflight
SYNCHRONIZE_CACHE and READ(10) commands, and verifies immediate
completion without DPM watchdog timeouts, along with the scsi_lib KUnit
test suite.

Changes in v2:
- Track sense_urb in uas_cmd_info and complete only the command owning
  the failed status URB in uas_stat_cmplt() instead of looping across
  all devinfo->cmnd[] slots and orphaning other commands' sense URBs.
- Set DID_NO_CONNECT only on -ENODEV and -ESHUTDOWN in uas_stat_cmplt()
  and uas_data_cmplt(), and DID_ERROR on other status/data URB errors.
- Clear pending submit and work flags and free unsubmitted URBs when
  completing commands on status URB or partial submission failure.
- Unlink already-submitted status and data URBs in
  uas_queuecommand_lck() when a later URB submission fails, and remove
  the unused out label.
- Add Fixes tags to all three patches.

v1:
  https://lore.kernel.org/r/20261113003536.3622755-1-sarthakkukreti@google.com

Sarthak Kukreti (3):
  usb: uas: complete command on status URB error
  usb: uas: fail command submission on fatal USB errors
  scsi: core: do not retry passthrough requests on disconnected targets

 drivers/scsi/scsi_lib.c      |   5 ++
 drivers/scsi/scsi_lib_test.c |   9 ++-
 drivers/usb/storage/uas.c    | 128 +++++++++++++++++++++++++++++------
 3 files changed, 122 insertions(+), 20 deletions(-)

-- 
2.56.0.611.g1030f0b940-goog