[PATCH v15 08/19] scsi: sd: Support sorting commands by LBA before resubmitting

[Bart Van Assche <bvanassche@acm.org>]

Support sorting SCSI commands by LBA before the SCSI error handler
resubmits these commands. This is necessary when resubmitting zoned writes
(REQ_OP_WRITE) if multiple writes have been queued for a single zone.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/sd.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 530918cbfce2..63bb01ddadde 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -47,6 +47,7 @@
 #include <linux/blkpg.h>
 #include <linux/blk-pm.h>
 #include <linux/delay.h>
+#include <linux/list_sort.h>
 #include <linux/major.h>
 #include <linux/mutex.h>
 #include <linux/string_helpers.h>
@@ -2058,6 +2059,38 @@ static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 	return eh_disp;
 }
 
+static int sd_cmp_sector(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);
+	struct request *rq_a = scsi_cmd_to_rq(a);
+	struct request *rq_b = scsi_cmd_to_rq(b);
+	bool use_zwl_a = rq_a->q->limits.use_zone_write_lock;
+	bool use_zwl_b = rq_b->q->limits.use_zone_write_lock;
+
+	/*
+	 * Order the commands that need zone write locking after the commands
+	 * that do not need zone write locking. Order the commands that do not
+	 * need zone write locking by LBA. Do not reorder the commands that
+	 * need zone write locking. See also the comment above the list_sort()
+	 * definition.
+	 */
+	if (use_zwl_a || use_zwl_b)
+		return use_zwl_a > use_zwl_b;
+	return blk_rq_pos(rq_a) > blk_rq_pos(rq_b);
+}
+
+static void sd_prepare_resubmit(struct list_head *cmd_list)
+{
+	/*
+	 * Sort pending SCSI commands in starting sector order. This is
+	 * important if one of the SCSI devices associated with @shost is a
+	 * zoned block device for which zone write locking is disabled.
+	 */
+	list_sort(NULL, cmd_list, sd_cmp_sector);
+}
+
 static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
 {
 	struct request *req = scsi_cmd_to_rq(scmd);
@@ -4014,6 +4047,7 @@ static struct scsi_driver sd_template = {
 	.done			= sd_done,
 	.eh_action		= sd_eh_action,
 	.eh_reset		= sd_eh_reset,
+	.eh_prepare_resubmit	= sd_prepare_resubmit,
 };
 
 /**