bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-v3

bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-v3

Changes in V3:

In case of error, V2 restored the previous number of segments but left
the BIO_SEG_FLAG set.
To avoid problems, after the page is removed from the bio vec,
V3 performs a recount of the segments in the error code path.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>