Commit 7e249690 authored Aug 17, 2020 by Ming Lei Committed by Jens Axboe Sep 02, 2020

block: allow for_each_bvec to support zero len bvec



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: syzbot <syzbot+61acc40a49a3e46e25ea@syzkaller.appspotmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Tetsuo 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: Jens Axboe <axboe@kernel.dk>

parent e11d80a8

include/linux/bvec.h

+8 −1

Original line number	Diff line number	Diff line
		@@ -117,11 +117,18 @@ 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) \

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