[PATCH v14 06/19] scsi: core: Introduce a mechanism for reordering requests in the error handler

Bart Van Assche
2023-10-23T21:57:08Z

Introduce the .eh_needs_prepare_resubmit and the .eh_prepare_resubmit
function pointers in struct scsi_driver. Make the error handler call
.eh_prepare_resubmit() before resubmitting commands if any of the
.eh_needs_prepare_resubmit() invocations return true. A later patch
will use this functionality to sort SCSI commands by LBA from inside
the SCSI disk driver before these are resubmitted by the error handler.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/scsi_error.c | 51 ++++++++++++++++++++++++++++++++++++++
drivers/scsi/scsi_priv.h | 2 ++
include/scsi/scsi_driver.h | 1 +
include/scsi/scsi_host.h | 6 +++++
4 files changed, 60 insertions(+)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 7390131e7f0a..a9588188e8a6 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -27,6 +27,7 @@
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
+#include <linux/list_sort.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
@@ -2186,6 +2187,54 @@ void scsi_eh_ready_devs(struct Scsi_Host *shost,
}
EXPORT_SYMBOL_GPL(scsi_eh_ready_devs);

+/*
+ * Comparison function for sorting SCSI commands by ULD driver.
+ */
+static int scsi_cmp_uld(void *priv, const struct list_head *_a,
+ const struct list_head *_b)
+{
+ struct scsi_cmnd *a = list_entry(_a, typeof(*a), eh_entry);
+ struct scsi_cmnd *b = list_entry(_b, typeof(*b), eh_entry);
+
+ /* See also the comment above the list_sort() definition. */
+ return scsi_cmd_to_driver(a) > scsi_cmd_to_driver(b);
+}
+
+void scsi_call_prepare_resubmit(struct Scsi_Host *shost,
+ struct list_head *done_q)
+{
+ struct scsi_cmnd *scmd, *next;
+
+ if (!shost->hostt->needs_prepare_resubmit)
+ return;
+
+ if (list_empty(done_q))
+ return;
+
+ /* Sort pending SCSI commands by ULD. */
+ list_sort(NULL, done_q, scsi_cmp_uld);
+
+ /*
+ * Call .eh_prepare_resubmit for each range of commands with identical
+ * ULD driver pointer.
+ */
+ list_for_each_entry_safe(scmd, next, done_q, eh_entry) {
+ struct scsi_driver *uld =
+ scmd->device ? scsi_cmd_to_driver(scmd) : NULL;
+ struct list_head *prev, uld_cmd_list;
+
+ while (&next->eh_entry != done_q &&
+ scsi_cmd_to_driver(next) == uld)
+ next = list_next_entry(next, eh_entry);
+ if (!uld->eh_prepare_resubmit)
+ continue;
+ prev = scmd->eh_entry.prev;
+ list_cut_position(&uld_cmd_list, prev, next->eh_entry.prev);
+ uld->eh_prepare_resubmit(&uld_cmd_list);
+ list_splice(&uld_cmd_list, prev);
+ }
+}
+
/**
* scsi_eh_flush_done_q - finish processed commands or retry them.
* @shost: SCSI host pointer.
@@ -2195,6 +2244,8 @@ void scsi_eh_flush_done_q(struct Scsi_Host *shost, struct list_head *done_q)
{
struct scsi_cmnd *scmd, *next;

+ scsi_call_prepare_resubmit(shost, done_q);
+
list_for_each_entry_safe(scmd, next, done_q, eh_entry) {
list_del_init(&scmd->eh_entry);
if (scsi_device_online(scmd->device) &&
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 3f0dfb97db6b..2caf4bcb072a 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -101,6 +101,8 @@ int scsi_eh_get_sense(struct list_head *work_q,
struct list_head *done_q);
bool scsi_noretry_cmd(struct scsi_cmnd *scmd);
void scsi_eh_done(struct scsi_cmnd *scmd);
+void scsi_call_prepare_resubmit(struct Scsi_Host *shost,
+ struct list_head *done_q);

/* scsi_lib.c */
extern void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd);
diff --git a/include/scsi/scsi_driver.h b/include/scsi/scsi_driver.h
index 4ce1988b2ba0..2b11be896eee 100644
--- a/include/scsi/scsi_driver.h
+++ b/include/scsi/scsi_driver.h
@@ -18,6 +18,7 @@ struct scsi_driver {
int (*done)(struct scsi_cmnd *);
int (*eh_action)(struct scsi_cmnd *, int);
void (*eh_reset)(struct scsi_cmnd *);
+ void (*eh_prepare_resubmit)(struct list_head *cmd_list);
};
#define to_scsi_driver(drv) \
container_of((drv), struct scsi_driver, gendrv)
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 49f768d0ff37..3e07e5b1a70c 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -461,6 +461,12 @@ struct scsi_host_template {
/* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
unsigned queuecommand_may_block:1;

+ /*
+ * The scsi_driver .eh_prepare_resubmit function must be called by
+ * the SCSI error handler.
+ */
+ unsigned needs_prepare_resubmit:1;
+
/*
* Countdown for host blocking with no commands outstanding.
*/