[PATCH v8 4/9] scsi: sd: Sort commands by LBA before resubmitting

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

Sort 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.

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/sd.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3c668cfb146d..4d9c6ad11cca 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>
@@ -117,6 +118,7 @@ static void sd_uninit_command(struct scsi_cmnd *SCpnt);
 static int sd_done(struct scsi_cmnd *);
 static void sd_eh_reset(struct scsi_cmnd *);
 static int sd_eh_action(struct scsi_cmnd *, int);
+static void sd_prepare_resubmit(struct list_head *cmd_list);
 static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
 static void scsi_disk_release(struct device *cdev);
 
@@ -617,6 +619,7 @@ 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,
 };
 
 /*
@@ -2018,6 +2021,26 @@ 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);
+
+	/* See also the comment above the list_sort() definition. */
+	return blk_rq_pos(scsi_cmd_to_rq(a)) > blk_rq_pos(scsi_cmd_to_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);