UBI: add auto-resize feature

The problem: NAND flashes have different amount of initial bad physical
eraseblocks (marked as bad by the manufacturer). For example, for 256MiB
Samsung OneNAND flash there might be from 0 to 40 bad initial eraseblocks,
which is about 2%. When UBI is used as the base system, one needs to know
the exact amount of good physical eraseblocks, because this number is
needed to create the UBI image which is put to the devices during
production. But this number is not know, which forces us to use the
minimum number of good physical eraseblocks. And UBI additionally
reserves some percentage of physical eraseblocks for bad block handling
(default is 1%), so we have 1-3% of PEBs reserved at the end, depending
on the amount of initial bad PEBs. But it is desired to always have
1% (or more, depending on the configuration).

Solution: this patch adds an "auto-resize" flag to the volume table.
The volume which has the "auto-resize" flag will automatically be re-sized
(enlarged) on the first UBI initialization. UBI clears the flag when
the volume is re-sized. Only one volume may have the "auto-resize" flag.

So, the production UBI image may have one volume with "auto-resize"
flag set, and its size is automatically adjusted on the first boot
of the device.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 64 insertions, 5 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 8b4573559df..4e761e957de 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -366,9 +366,6 @@ static int uif_init(struct ubi_device *ubi)
 	int i, err;
 	dev_t dev;
 
-	mutex_init(&ubi->volumes_mutex);
-	spin_lock_init(&ubi->volumes_lock);
-
 	sprintf(ubi->ubi_name, UBI_NAME_STR "%d", ubi->ubi_num);
 
 	/*
@@ -624,6 +621,58 @@ static int io_init(struct ubi_device *ubi)
 }
 
 /**
+ * autoresize - re-size the volume which has the "auto-resize" flag set.
+ * @ubi: UBI device description object
+ * @vol_id: ID of the volume to re-size
+ *
+ * This function re-sizes the volume marked by the @UBI_VTBL_AUTORESIZE_FLG in
+ * the volume table to the largest possible size. See comments in ubi-header.h
+ * for more description of the flag. Returns zero in case of success and a
+ * negative error code in case of failure.
+ */
+static int autoresize(struct ubi_device *ubi, int vol_id)
+{
+	struct ubi_volume_desc desc;
+	struct ubi_volume *vol = ubi->volumes[vol_id];
+	int err, old_reserved_pebs = vol->reserved_pebs;
+
+	/*
+	 * Clear the auto-resize flag in the volume in-memory copy of the
+	 * volume table, and 'ubi_resize_volume()' will propogate this change
+	 * to the flash.
+	 */
+	ubi->vtbl[vol_id].flags &= ~UBI_VTBL_AUTORESIZE_FLG;
+
+	if (ubi->avail_pebs == 0) {
+		struct ubi_vtbl_record vtbl_rec;
+
+		/*
+		 * No avalilable PEBs to re-size the volume, clear the flag on
+		 * flash and exit.
+		 */
+		memcpy(&vtbl_rec, &ubi->vtbl[vol_id],
+		       sizeof(struct ubi_vtbl_record));
+		err = ubi_change_vtbl_record(ubi, vol_id, &vtbl_rec);
+		if (err)
+			ubi_err("cannot clean auto-resize flag for volume %d",
+				vol_id);
+	} else {
+		desc.vol = vol;
+		err = ubi_resize_volume(&desc,
+					old_reserved_pebs + ubi->avail_pebs);
+		if (err)
+			ubi_err("cannot auto-resize volume %d", vol_id);
+	}
+
+	if (err)
+		return err;
+
+	ubi_msg("volume %d (\"%s\") re-sized from %d to %d LEBs", vol_id,
+		vol->name, old_reserved_pebs, vol->reserved_pebs);
+	return 0;
+}
+
+/**
  * ubi_attach_mtd_dev - attach an MTD device.
  * @mtd_dev: MTD device description object
  * @ubi_num: number to assign to the new UBI device
@@ -699,6 +748,12 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	ubi->mtd = mtd;
 	ubi->ubi_num = ubi_num;
 	ubi->vid_hdr_offset = vid_hdr_offset;
+	ubi->autoresize_vol_id = -1;
+
+	mutex_init(&ubi->buf_mutex);
+	mutex_init(&ubi->ckvol_mutex);
+	mutex_init(&ubi->volumes_mutex);
+	spin_lock_init(&ubi->volumes_lock);
 
 	dbg_msg("attaching mtd%d to ubi%d: VID header offset %d",
 		mtd->index, ubi_num, vid_hdr_offset);
@@ -707,8 +762,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	if (err)
 		goto out_free;
 
-	mutex_init(&ubi->buf_mutex);
-	mutex_init(&ubi->ckvol_mutex);
 	ubi->peb_buf1 = vmalloc(ubi->peb_size);
 	if (!ubi->peb_buf1)
 		goto out_free;
@@ -730,6 +783,12 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 		goto out_free;
 	}
 
+	if (ubi->autoresize_vol_id != -1) {
+		err = autoresize(ubi, ubi->autoresize_vol_id);
+		if (err)
+			goto out_detach;
+	}
+
 	err = uif_init(ubi);
 	if (err)
 		goto out_detach;