If a non-passthrough command is terminated with a CHECK CONDITION, the scsi error recovery code reuses the failed command scsi_cmnd structure to process error recovery request sense. To preserve information regarding the failed command, the functions scsi_eh_prep_cmnd() and scsi_eh_restore_cmnd() respectively save and restore the original command information. However, the resid field of the failed command request structure is not preserved and reused for the request sense handling, leading to the original command having an incorrect resid when: A) The command is not retried and terminated with an error B) The command completes after retry and the underlying LLD does not set resid for a fully completed command (resid=0) The first patch of this series addresses case (A) above by adding resid as part of the command information saved using struct scsi_eh_save. Case B can be observed with a WD My Book USB disks when a read or write command is sent to the disk while the disk is in deep sleep mode (spun down) due to a long period of inactivity (~30min). In such case, the following command sequence happen: 1) The read or write command is terminated after a few seconds with CHECK CONDITION and an asc/ascq of 04/01 (LOGICAL UNIT IS IN PROCESS OF BECOMING READY) 2) In response to this failure, the USB mass storage driver triggers autosense processing, reusing the command descriptor to issue a request sense command with a 96B sense buffer size. The reply to this command gives a NOT READY / LOGICAL UNIT IS IN PROCESS OF BECOMING READY sense of 18B, resulting in a resid of 78B. 3) The original command is retried and failed again, with step 2 repeated, until the drive spins up and becomes ready. 4) When the original command completes after the drive has become ready, the request sense command resid of 78B is seen by the scsi disk driver sd_done() function and wrongly generates a warning about the unaligned value reported. This problem is fixed in patch 2 by always setting a command resid to 0 when there is no residual in usb_stor_Bulk_transport(). Note that usb_stor_CB_transport() does not need changes since usb_stor_bulk_srb() always sets the resid for a completed command, regardless of the residual value. Damien Le Moal (2): scsi: save/restore command resid for error handling usb: Clear scsi command resid when residue is 0 drivers/scsi/scsi_error.c | 2 ++ drivers/usb/storage/transport.c | 9 +++++++++ include/scsi/scsi_eh.h | 1 + 3 files changed, 12 insertions(+) -- 2.21.0
