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From: Kent Overstreet <kent.overstreet@gmail.com>
To: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	linux-mm@kvack.org, Jens Axboe <axboe@kernel.dk>,
	Ingo Molnar <mingo@kernel.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Subject: [PATCH 08/10] block: Add warning for bi_next not NULL in bio_endio()
Date: Tue,  8 May 2018 21:33:56 -0400	[thread overview]
Message-ID: <20180509013358.16399-9-kent.overstreet@gmail.com> (raw)
In-Reply-To: <20180509013358.16399-1-kent.overstreet@gmail.com>

Recently found a bug where a driver left bi_next not NULL and then
called bio_endio(), and then the submitter of the bio used
bio_copy_data() which was treating src and dst as lists of bios.

Fixed that bug by splitting out bio_list_copy_data(), but in case other
things are depending on bi_next in weird ways, add a warning to help
avoid more bugs like that in the future.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
 block/bio.c      | 3 +++
 block/blk-core.c | 8 +++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index ce8e259f9a..5c81391100 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1775,6 +1775,9 @@ void bio_endio(struct bio *bio)
 	if (!bio_integrity_endio(bio))
 		return;
 
+	if (WARN_ONCE(bio->bi_next, "driver left bi_next not NULL"))
+		bio->bi_next = NULL;
+
 	/*
 	 * Need to have a real endio function for chained bios, otherwise
 	 * various corner cases will break (like stacking block devices that
diff --git a/block/blk-core.c b/block/blk-core.c
index 66f24798ef..f3cf79198a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -204,6 +204,10 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 	bio_advance(bio, nbytes);
 
 	/* don't actually finish bio if it's part of flush sequence */
+	/*
+	 * XXX this code looks suspicious - it's not consistent with advancing
+	 * req->bio in caller
+	 */
 	if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
 		bio_endio(bio);
 }
@@ -2982,8 +2986,10 @@ bool blk_update_request(struct request *req, blk_status_t error,
 		struct bio *bio = req->bio;
 		unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
 
-		if (bio_bytes == bio->bi_iter.bi_size)
+		if (bio_bytes == bio->bi_iter.bi_size) {
 			req->bio = bio->bi_next;
+			bio->bi_next = NULL;
+		}
 
 		/* Completion has already been traced */
 		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
-- 
2.17.0

  parent reply	other threads:[~2018-05-09  1:35 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-09  1:33 [PATCH 00/10] Misc block layer patches for bcachefs Kent Overstreet
2018-05-09  1:33 ` [PATCH 01/10] mempool: Add mempool_init()/mempool_exit() Kent Overstreet
2018-05-09  7:54   ` Johannes Thumshirn
2018-05-11 21:11   ` Jens Axboe
2018-05-14 19:11     ` Kent Overstreet
2018-05-09  1:33 ` [PATCH 02/10] block: Convert bio_set to mempool_init() Kent Overstreet
2018-05-18 16:20   ` Christoph Hellwig
2018-05-18 16:21     ` Christoph Hellwig
2018-05-18 17:36     ` Kent Overstreet
2018-05-09  1:33 ` [PATCH 03/10] block: Add bioset_init()/bioset_exit() Kent Overstreet
2018-05-09  1:33 ` [PATCH 04/10] block: Use bioset_init() for fs_bio_set Kent Overstreet
2018-05-09  1:33 ` [PATCH 05/10] block: Add bio_copy_data_iter(), zero_fill_bio_iter() Kent Overstreet
2018-05-09  1:33 ` [PATCH 06/10] block: Split out bio_list_copy_data() Kent Overstreet
2018-05-09  1:33 ` [PATCH 07/10] block: Add missing flush_dcache_page() call Kent Overstreet
2018-05-09  1:33 ` Kent Overstreet [this message]
2018-05-09  1:33 ` [PATCH 09/10] block: Export bio check/set pages_dirty Kent Overstreet
2018-05-09  1:33 ` [PATCH 10/10] block: Add sysfs entry for fua support Kent Overstreet
2018-05-11 21:13 ` [PATCH 00/10] Misc block layer patches for bcachefs Jens Axboe
2018-05-18 16:23   ` Christoph Hellwig
2018-05-18 16:33     ` Jens Axboe
2018-05-14 19:24 ` Jens Axboe
2018-05-14 19:24   ` Kent Overstreet
2018-05-17 20:54 ` Bart Van Assche
2018-05-18  9:06   ` Kent Overstreet
2018-05-18 15:12     ` Bart Van Assche
2018-05-20 22:17       ` Kent Overstreet
2018-05-20 22:19         ` Bart Van Assche
2018-05-20 22:31           ` Kent Overstreet
2018-05-20 22:35             ` Bart Van Assche
2018-05-20 23:00               ` Kent Overstreet
2018-05-20 23:10                 ` Bart Van Assche
2018-05-20 23:21               ` Kent Overstreet
2018-05-20 23:40                 ` Bart Van Assche
2018-05-20 23:58                   ` Kent Overstreet
2018-05-21 15:11                     ` Bart Van Assche
2018-05-21 18:37                       ` Omar Sandoval
2018-05-21 18:46                         ` Bart Van Assche
2018-05-22 22:01         ` Bart Van Assche
2018-05-18  7:48 [PATCH 00/10] RFC: assorted bcachefs patches Kent Overstreet
2018-05-18  7:49 ` [PATCH 08/10] block: Add warning for bi_next not NULL in bio_endio() Kent Overstreet
2018-05-18  9:00   ` Johannes Thumshirn

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