The get_mtd_device() function returns error pointers on failure and if we
don't handle it, it leads to a crash.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Joern Engel <joern@logfs.org>
Erases for block devices were always just emulated by writing 0xff.
Some time back the write was removed and only the page cache was
changed to 0xff. Superficialy a good idea with two problems:
1. Touching the page cache isn't necessary either.
2. However, writing out 0xff _is_ necessary for the journal. As the
journal is scanned linearly, an old non-overwritten commit entry
can be used on next mount and cause havoc.
This should fix both aspects.
