iomap: Make sure iomap_end is called after iomap_begin

mainline inclusion
from mainline-5.9-rc1
commit 856473cd
category: bugfix
bugzilla: 40769
CVE: NA
---------------------------

Make sure iomap_end is always called when iomap_begin succeeds.

Without this fix, iomap_end won't be called when a filesystem's
iomap_begin operation returns an invalid mapping, bypassing any
unlocking done in iomap_end.  With this fix, the unlocking will still
happen.

This bug was found by Bob Peterson during code review.  It's unlikely
that such iomap_begin bugs will survive to affect users, so backporting
this fix seems unnecessary.

Fixes: ae259a9c ("fs: introduce iomap infrastructure")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[fs/iomap/apply.c not exist, instead fs/iomap.c]
Signed-off-by: yangerkun <yangerkun@huawei...>