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    Subject[PATCH 3.16 128/346] ubi: Make volume resize power cut aware
    3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Richard Weinberger <richard@nod.at>

    commit 4946784bd3924b1374f05eebff2fd68660bae866 upstream.

    When the volume resize operation shrinks a volume,
    LEBs will be unmapped. Since unmapping will not erase these
    LEBs immediately we have to wait for that operation to finish.
    Otherwise in case of a power cut right after writing the new
    volume table the UBI attach process can find more LEBs than the
    volume table knows. This will render the UBI image unattachable.

    Fix this issue by waiting for erase to complete and write the new
    volume table afterward.

    Reported-by: Boris Brezillon <boris.brezillon@free-electrons.com>
    Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
    Signed-off-by: Richard Weinberger <richard@nod.at>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/mtd/ubi/vmt.c | 25 ++++++++++++++++++-------
    1 file changed, 18 insertions(+), 7 deletions(-)

    --- a/drivers/mtd/ubi/vmt.c
    +++ b/drivers/mtd/ubi/vmt.c
    @@ -534,13 +534,6 @@ int ubi_resize_volume(struct ubi_volume_
    spin_unlock(&ubi->volumes_lock);
    }

    - /* Change volume table record */
    - vtbl_rec = ubi->vtbl[vol_id];
    - vtbl_rec.reserved_pebs = cpu_to_be32(reserved_pebs);
    - err = ubi_change_vtbl_record(ubi, vol_id, &vtbl_rec);
    - if (err)
    - goto out_acc;
    -
    if (pebs < 0) {
    for (i = 0; i < -pebs; i++) {
    err = ubi_eba_unmap_leb(ubi, vol, reserved_pebs + i);
    @@ -558,6 +551,24 @@ int ubi_resize_volume(struct ubi_volume_
    spin_unlock(&ubi->volumes_lock);
    }

    + /*
    + * When we shrink a volume we have to flush all pending (erase) work.
    + * Otherwise it can happen that upon next attach UBI finds a LEB with
    + * lnum > highest_lnum and refuses to attach.
    + */
    + if (pebs < 0) {
    + err = ubi_wl_flush(ubi, vol_id, UBI_ALL);
    + if (err)
    + goto out_acc;
    + }
    +
    + /* Change volume table record */
    + vtbl_rec = ubi->vtbl[vol_id];
    + vtbl_rec.reserved_pebs = cpu_to_be32(reserved_pebs);
    + err = ubi_change_vtbl_record(ubi, vol_id, &vtbl_rec);
    + if (err)
    + goto out_acc;
    +
    vol->reserved_pebs = reserved_pebs;
    if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
    vol->used_ebs = reserved_pebs;
    \
     
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