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Commit 84c041c1 authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman
Browse files

block: allow for_each_bvec to support zero len bvec 



commit 7e24969022cbd61ddc586f14824fc205661bb124 upstream.

Block layer usually doesn't support or allow zero-length bvec. Since
commit 1bdc76ae ("iov_iter: use bvec iterator to implement
iterate_bvec()"), iterate_bvec() switches to bvec iterator. However,
Al mentioned that 'Zero-length segments are not disallowed' in iov_iter.

Fixes for_each_bvec() so that it can move on after seeing one zero
length bvec.

Fixes: 1bdc76ae ("iov_iter: use bvec iterator to implement iterate_bvec()")
Reported-by: default avatarsyzbot <syzbot+61acc40a49a3e46e25ea@syzkaller.appspotmail.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Tested-by: default avatarTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2262077.html


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b6e4827c

include/linux/bvec.h

+8 −1
Original line number Diff line number Diff line
@@ -110,11 +110,18 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv, 
	return true;

}



static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)

{

	iter->bi_bvec_done = 0;

	iter->bi_idx++;

}



#define for_each_bvec(bvl, bio_vec, iter, start)			\

	for (iter = (start);						\

	     (iter).bi_size &&						\

		((bvl = bvec_iter_bvec((bio_vec), (iter))), 1);	\

	     bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))

	     (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter),	\

		     (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))



/* for iterating one bio from start to end */

#define BVEC_ITER_ALL_INIT (struct bvec_iter)				\