iomap: release pages on atomic dio size mismatch

iomap: release pages on atomic dio size mismatch

If bio_iov_iter_get_pages() or the bounce helper succeeds but builds a
short bio, the REQ_ATOMIC size check rejects it before submission.  The
old error path only dropped the bio reference, leaving any pages already
attached to the bio unreleased.

Release or unbounce the pages before falling through to out_put_bio on
this error path.

This bug was reported by sashiko:
https://sashiko.dev/#/patchset/20260608073134.95964-1-changfengnan%40bytedance.com

Fixes: 9e0933c21c12 ("fs: iomap: Atomic write support")
Signed-off-by: Fengnan Chang <changfengnan@bytedance.com>
Link: https://patch.msgid.link/20260612044041.10677-1-changfengnan@bytedance.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>