[PATCH] mtd: ubi: Use UBI_METAONLY constraint for renames

[Andrew Murray]

Renaming a volume does not alter nor read volume data - thus the existing
UBI_READWRITE constraint can be weakened. This patch provides a new
UBI_METAONLY constraint and updates the UBI rename logic to use it.

This change permits the rename of a mounted volume which enables support
for additional methods of firmware upgrade - see discussion at
https://patchwork.ozlabs.org/patch/398784

This patch differs from that of the original discussion through the addition
on an additional 'break' statement.

Cc: Ezequiel Garcia <ezequiel.garcia at free-electrons.com>
Tested-by: Andrew Murray <amurray at embedded-bits.co.uk>
Signed-off-by: Richard Weinberger <richard at nod.at>
Signed-off-by: Andrew Murray <amurray at embedded-bits.co.uk>
---
 drivers/mtd/ubi/cdev.c  |  2 +-
 drivers/mtd/ubi/kapi.c  | 12 +++++++++++-
 drivers/mtd/ubi/ubi.h   |  5 ++++-
 include/linux/mtd/ubi.h |  3 ++-
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index 7646220..4c4c455 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -731,7 +731,7 @@ static int rename_volumes(struct ubi_device *ubi,
 			goto out_free;
 		}
 
-		re->desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_READWRITE);
+		re->desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_METAONLY);
 		if (IS_ERR(re->desc)) {
 			err = PTR_ERR(re->desc);
 			ubi_err("cannot open volume %d, error %d", vol_id, err);
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index 3aac1ac..b470619 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -137,7 +137,7 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
 		return ERR_PTR(-EINVAL);
 
 	if (mode != UBI_READONLY && mode != UBI_READWRITE &&
-	    mode != UBI_EXCLUSIVE)
+	    mode != UBI_EXCLUSIVE && mode != UBI_METAONLY)
 		return ERR_PTR(-EINVAL);
 
 	/*
@@ -186,6 +186,12 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
 			goto out_unlock;
 		vol->exclusive = 1;
 		break;
+
+	case UBI_METAONLY:
+		if (vol->metaonly)
+			goto out_unlock;
+		vol->metaonly = 1;
+		break;
 	}
 	get_device(&vol->dev);
 	vol->ref_count += 1;
@@ -343,6 +349,10 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
 		break;
 	case UBI_EXCLUSIVE:
 		vol->exclusive = 0;
+		break;
+	case UBI_METAONLY:
+		vol->metaonly = 0;
+		break;
 	}
 	vol->ref_count -= 1;
 	spin_unlock(&ubi->volumes_lock);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 7bf4163..629973f 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -260,6 +260,7 @@ struct ubi_fm_pool {
  * @readers: number of users holding this volume in read-only mode
  * @writers: number of users holding this volume in read-write mode
  * @exclusive: whether somebody holds this volume in exclusive mode
+ * @metaonly: whether somebody is altering only meta data of this volume
  *
  * @reserved_pebs: how many physical eraseblocks are reserved for this volume
  * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
@@ -308,6 +309,7 @@ struct ubi_volume {
 	int readers;
 	int writers;
 	int exclusive;
+	int metaonly;
 
 	int reserved_pebs;
 	int vol_type;
@@ -389,7 +391,8 @@ struct ubi_debug_info {
  * @volumes_lock: protects @volumes, @rsvd_pebs, @avail_pebs, beb_rsvd_pebs,
  *                @beb_rsvd_level, @bad_peb_count, @good_peb_count, @vol_count,
  *                @vol->readers, @vol->writers, @vol->exclusive,
- *                @vol->ref_count, @vol->mapping and @vol->eba_tbl.
+ *                @vol->metaonly, @vol->ref_count, @vol->mapping and
+ *                @vol->eba_tbl.
  * @ref_count: count of references on the UBI device
  * @image_seq: image sequence number recorded on EC headers
  *
diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
index c3918a0..1ace519 100644
--- a/include/linux/mtd/ubi.h
+++ b/include/linux/mtd/ubi.h
@@ -38,7 +38,8 @@
 enum {
 	UBI_READONLY = 1,
 	UBI_READWRITE,
-	UBI_EXCLUSIVE
+	UBI_EXCLUSIVE,
+	UBI_METAONLY
 };
 
 /**
-- 
1.8.3.2