[PATCH V3] scsi: save/restore command resid for error handling

[Damien Le Moal <damien.lemoal@wdc.com>]

When a non-passthrough command is terminated with CHECK CONDITION,
request sense is executed by hijacking the command descriptor. Since
scsi_eh_prep_cmnd() and scsi_eh_restore_cmnd() do not save/restore the
original command resid, the value returned on failure of the original
command is lost and replaced with the value set by the execution of the
request sense command. This value may in many instances be unaligned to
the device sector size, causing sd_done() to print a warning message
about the incorrect unaligned resid before the command is retried.

Fix this problem by saving the original command residual in struct
scsi_eh_save using scsi_eh_prep_cmnd() and restoring it in
scsi_eh_restore_cmnd(). In addition, to make sure that the request sense
command is executed with a correctly initialized command structure, also
reset the residual to 0 in scsi_eh_prep_cmnd() after saving the original
command value in struct scsi_eh_save.

Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
Changes from V2:
* Open code resid save/restore to keep the functions style
* rename struct scsi_eh_save resid field to resid_len to match struct
  scsi_request field name

Changes from V1:
* Dropped patch 2
* Add resid reset in scsi_eh_prep_cmnd()

 drivers/scsi/scsi_error.c | 3 +++
 include/scsi/scsi_eh.h    | 1 +
 2 files changed, 4 insertions(+)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 1c470e31ae81..ae2fa170f6ad 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -967,6 +967,7 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
 	ses->data_direction = scmd->sc_data_direction;
 	ses->sdb = scmd->sdb;
 	ses->result = scmd->result;
+	ses->resid_len = scmd->req.resid_len;
 	ses->underflow = scmd->underflow;
 	ses->prot_op = scmd->prot_op;
 	ses->eh_eflags = scmd->eh_eflags;
@@ -977,6 +978,7 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
 	memset(scmd->cmnd, 0, BLK_MAX_CDB);
 	memset(&scmd->sdb, 0, sizeof(scmd->sdb));
 	scmd->result = 0;
+	scmd->req.resid_len = 0;
 
 	if (sense_bytes) {
 		scmd->sdb.length = min_t(unsigned, SCSI_SENSE_BUFFERSIZE,
@@ -1029,6 +1031,7 @@ void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
 	scmd->sc_data_direction = ses->data_direction;
 	scmd->sdb = ses->sdb;
 	scmd->result = ses->result;
+	scmd->req.resid_len = ses->resid_len;
 	scmd->underflow = ses->underflow;
 	scmd->prot_op = ses->prot_op;
 	scmd->eh_eflags = ses->eh_eflags;
diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
index 3810b340551c..6bd5ed695a5e 100644
--- a/include/scsi/scsi_eh.h
+++ b/include/scsi/scsi_eh.h
@@ -32,6 +32,7 @@ extern int scsi_ioctl_reset(struct scsi_device *, int __user *);
 struct scsi_eh_save {
 	/* saved state */
 	int result;
+	unsigned int resid_len;
 	int eh_eflags;
 	enum dma_data_direction data_direction;
 	unsigned underflow;
-- 
2.21.0