[dm-devel] [PATCH] dm linear: disable WRITE SAME if it fails

[alex chen]

The original commit f84cb8a46a771f36a04a02c61ea635c968ed5f6a("dm mpath:
disable WRITE SAME if it fails") disables WRITE SAME in the DM multipath
device if it fails, but when the DM linear device stacks ontop of the
multipath device it doesn't help.

this patch adds DM linear end_io method to catch WRITE SAME errors and
disables WRITE SAME in the DM linear device's queue_limits if an
underlying device disables it.

Before this patch:

dm linear device(dm-20): ocfs2-fs;
multipath device(dm-6);
scsi device(sdt,sdu);

After a WRITE SAME bio fails, the DM linear device does not disable the
WRITE SAME, although the underlying device(DM multipath device) has
disabled WRITE SAME.

cat /sys/block/dm-20/queue/write_same_max_bytes
33553920
cat /sys/block/dm-6/queue/write_same_max_bytes
0
cat /sys/block/sdt/queue/write_same_max_bytes
0
cat /sys/block/sdu/queue/write_same_max_bytes
0

After this patch:

dm linear device(dm-20): ocfs2-fs;
multipath device(dm-6);
scsi device(sdt,sdu);

After a WRITE SAME bio fails, the underlying device(DM multipath
device) disables WRITE SAME and then the DM linear device also disables
WRITE SAME.

cat /sys/block/dm-20/queue/write_same_max_bytes
0
cat /sys/block/dm-6/queue/write_same_max_bytes
0
cat /sys/block/sdt/queue/write_same_max_bytes
0
cat /sys/block/sdu/queue/write_same_max_bytes
0

Signed-off-by: alex.chen <alex.chen at huawei.com>
---
 drivers/md/dm-linear.c | 26 +++++++++++++++++++++++++-
 drivers/md/dm.c        |  2 +-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 53e848c..eaf86a5 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -96,6 +96,29 @@ static int linear_map(struct dm_target *ti, struct
bio *bio)
 	return DM_MAPIO_REMAPPED;
 }

+static int linear_end_io(struct dm_target *ti, struct bio *bio, int error)
+{
+	struct linear_c *lc = ti->private;
+	struct block_device *bdev;
+	struct queue_limits *limits;
+	struct queue_limits *bdev_limits;
+
+	if (!error)
+		return error;
+
+	if (unlikely(bio->bi_rw & REQ_WRITE_SAME)) {
+		bdev = lc->dev->bdev;
+		bdev_limits = &bdev->bd_disk->queue->limits;
+
+		limits = dm_get_queue_limits(dm_table_get_md(ti->table));
+
+		if ((!bdev_limits->max_write_same_sectors) &&
+				limits->max_write_same_sectors)
+			limits->max_write_same_sectors = 0;
+	}
+
+	return error;
+}
 static void linear_status(struct dm_target *ti, status_type_t type,
 			  unsigned status_flags, char *result, unsigned maxlen)
 {
@@ -155,11 +178,12 @@ static int linear_iterate_devices(struct dm_target
*ti,

 static struct target_type linear_target = {
 	.name   = "linear",
-	.version = {1, 2, 1},
+	.version = {1, 2, 2},
 	.module = THIS_MODULE,
 	.ctr    = linear_ctr,
 	.dtr    = linear_dtr,
 	.map    = linear_map,
+	.end_io = linear_end_io,
 	.status = linear_status,
 	.ioctl  = linear_ioctl,
 	.merge  = linear_merge,
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 8c53b09..4337025 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -770,7 +770,7 @@ static void clone_endio(struct bio *bio, int error)

 	if (endio) {
 		r = endio(tio->ti, bio, error);
-		if (r < 0 || r == DM_ENDIO_REQUEUE)
+		if (r <= 0 || r == DM_ENDIO_REQUEUE)
 			/*
 			 * error and requeue request are handled
 			 * in dec_pending().
-- 
1.8.4.3

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