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Subject[PATCH AUTOSEL 4.20 77/77] Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED"
Date
From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 947b7ac135b16aa60f9141ff72bd494eda0edb5e ]

We can't touch a bio after ->make_request_fn(), for all we know it could
already have been completed by the time this function returns.

This reverts commit 698cef173983b086977e633e46476e0f925ca01e.

Reported-by: syzbot+4df6ca820108fd248943@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-core.c | 11 -----------
block/blk-merge.c | 10 ++++++++++
2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 22260339f66f..deb56932f8c4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2449,18 +2449,7 @@ blk_qc_t generic_make_request(struct bio *bio)
/* Create a fresh bio_list for all subordinate requests */
bio_list_on_stack[1] = bio_list_on_stack[0];
bio_list_init(&bio_list_on_stack[0]);
-
- /*
- * Since we're recursing into make_request here, ensure
- * that we mark this bio as already having entered the queue.
- * If not, and the queue is going away, we can get stuck
- * forever on waiting for the queue reference to drop. But
- * that will never happen, as we're already holding a
- * reference to it.
- */
- bio_set_flag(bio, BIO_QUEUE_ENTERED);
ret = q->make_request_fn(q, bio);
- bio_clear_flag(bio, BIO_QUEUE_ENTERED);

/* sort new bios into those for a lower level
* and those for the same level
diff --git a/block/blk-merge.c b/block/blk-merge.c
index adfe835ab258..7695034f4b87 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -272,6 +272,16 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
/* there isn't chance to merge the splitted bio */
split->bi_opf |= REQ_NOMERGE;

+ /*
+ * Since we're recursing into make_request here, ensure
+ * that we mark this bio as already having entered the queue.
+ * If not, and the queue is going away, we can get stuck
+ * forever on waiting for the queue reference to drop. But
+ * that will never happen, as we're already holding a
+ * reference to it.
+ */
+ bio_set_flag(*bio, BIO_QUEUE_ENTERED);
+
bio_chain(split, *bio);
trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
generic_make_request(*bio);
--
2.19.1
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