[PATCH V2 1/6] md/raid0: don't leave mddev in an inconsistent state when takeover fails

[Zizhi Wo]

From: Zizhi Wo <wozizhi@xxxxxxxxxx>

raid0_takeover_raid45(), raid0_takeover_raid10() and raid0_takeover_raid1()
update mddev before create_strip_zones(), which can fail.

On failure, level_store() only rolls back new_level, new_layout,
new_chunk_sectors, raid_disks and delta_disks. The old personality is
therefore left with a reset resync_offset, cleared feature flags, and, for
raid1, the wrong chunk size.

Set only what create_strip_zones() needs before calling it, and move the
rest after it succeeds.

create_strip_zones() also rounds rdev->sectors, but the old levels do not
use it for I/O, so that is harmless. And mddev->degraded is already reset
by level_store() on success, so drop the redundant assignment in
raid0_takeover_raid10().

Fixes: 9af204cf720c ("md: Add support for Raid5->Raid0 and Raid10->Raid0 takeover")
Fixes: fc3a08b85b7a ("Add raid1->raid0 takeover support")
Signed-off-by: Zizhi Wo <wozizhi@xxxxxxxxxx>
---
 drivers/md/raid0.c | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 35e103f0c2c3..8157e1058a24 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -669,15 +669,16 @@ static void *raid0_takeover_raid45(struct mddev *mddev)
 	mddev->new_level = 0;
 	mddev->new_layout = 0;
 	mddev->new_chunk_sectors = mddev->chunk_sectors;
 	mddev->raid_disks--;
 	mddev->delta_disks = -1;
-	/* make sure it will be not marked as dirty */
-	mddev->resync_offset = MaxSector;
-	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
 
-	create_strip_zones(mddev, &priv_conf);
+	if (!create_strip_zones(mddev, &priv_conf)) {
+		/* make sure it will be not marked as dirty */
+		mddev->resync_offset = MaxSector;
+		mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
+	}
 
 	return priv_conf;
 }
 
 static void *raid0_takeover_raid10(struct mddev *mddev)
@@ -711,23 +712,25 @@ static void *raid0_takeover_raid10(struct mddev *mddev)
 	mddev->new_level = 0;
 	mddev->new_layout = 0;
 	mddev->new_chunk_sectors = mddev->chunk_sectors;
 	mddev->delta_disks = - mddev->raid_disks / 2;
 	mddev->raid_disks += mddev->delta_disks;
-	mddev->degraded = 0;
-	/* make sure it will be not marked as dirty */
-	mddev->resync_offset = MaxSector;
-	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
 
-	create_strip_zones(mddev, &priv_conf);
+	if (!create_strip_zones(mddev, &priv_conf)) {
+		/* make sure it will be not marked as dirty */
+		mddev->resync_offset = MaxSector;
+		mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
+	}
+
 	return priv_conf;
 }
 
 static void *raid0_takeover_raid1(struct mddev *mddev)
 {
 	struct r0conf *priv_conf;
 	int chunksect;
+	int old_chunk_sectors;
 
 	/* Check layout:
 	 *  - (N - 1) mirror drives must be already faulty
 	 */
 	if ((mddev->raid_disks - 1) != mddev->degraded) {
@@ -748,22 +751,29 @@ static void *raid0_takeover_raid1(struct mddev *mddev)
 
 	if ((chunksect << 9) < PAGE_SIZE)
 		/* array size does not allow a suitable chunk size */
 		return ERR_PTR(-EINVAL);
 
+	/* Save for rollback if create_strip_zones() fails */
+	old_chunk_sectors = mddev->chunk_sectors;
+
 	/* Set new parameters */
 	mddev->new_level = 0;
 	mddev->new_layout = 0;
 	mddev->new_chunk_sectors = chunksect;
 	mddev->chunk_sectors = chunksect;
 	mddev->delta_disks = 1 - mddev->raid_disks;
 	mddev->raid_disks = 1;
-	/* make sure it will be not marked as dirty */
-	mddev->resync_offset = MaxSector;
-	mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
 
-	create_strip_zones(mddev, &priv_conf);
+	if (!create_strip_zones(mddev, &priv_conf)) {
+		/* make sure it will be not marked as dirty */
+		mddev->resync_offset = MaxSector;
+		mddev_clear_unsupported_flags(mddev, UNSUPPORTED_MDDEV_FLAGS);
+	} else {
+		mddev->chunk_sectors = old_chunk_sectors;
+	}
+
 	return priv_conf;
 }
 
 static void *raid0_takeover(struct mddev *mddev)
 {
-- 
2.52.0