block: don't use blocking queue entered for recursive bio submits
If we end up splitting a bio and the queue goes away between the initial submission and the later split submission, then we can block forever in blk_queue_enter() waiting for the reference to drop to zero. This will never happen, since we already hold a reference. Mark a split bio as already having entered the queue, so we can just use the live non-blocking queue enter variant. Thanks to Tetsuo Handa for the analysis. Reported-by: syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>hifive-unleashed-5.1
parent
d00a11df69
commit
cd4a4ae468
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@ -2377,7 +2377,9 @@ blk_qc_t generic_make_request(struct bio *bio)
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if (bio->bi_opf & REQ_NOWAIT)
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if (bio->bi_opf & REQ_NOWAIT)
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flags = BLK_MQ_REQ_NOWAIT;
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flags = BLK_MQ_REQ_NOWAIT;
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if (blk_queue_enter(q, flags) < 0) {
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if (bio_flagged(bio, BIO_QUEUE_ENTERED))
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blk_queue_enter_live(q);
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else if (blk_queue_enter(q, flags) < 0) {
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if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))
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if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))
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bio_wouldblock_error(bio);
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bio_wouldblock_error(bio);
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else
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else
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@ -210,6 +210,16 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
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/* there isn't chance to merge the splitted bio */
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/* there isn't chance to merge the splitted bio */
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split->bi_opf |= REQ_NOMERGE;
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split->bi_opf |= REQ_NOMERGE;
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/*
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* Since we're recursing into make_request here, ensure
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* that we mark this bio as already having entered the queue.
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* If not, and the queue is going away, we can get stuck
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* forever on waiting for the queue reference to drop. But
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* that will never happen, as we're already holding a
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* reference to it.
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*/
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bio_set_flag(*bio, BIO_QUEUE_ENTERED);
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bio_chain(split, *bio);
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bio_chain(split, *bio);
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trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
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trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
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generic_make_request(*bio);
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generic_make_request(*bio);
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@ -229,6 +229,8 @@ struct bio {
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* throttling rules. Don't do it again. */
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* throttling rules. Don't do it again. */
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#define BIO_TRACE_COMPLETION 10 /* bio_endio() should trace the final completion
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#define BIO_TRACE_COMPLETION 10 /* bio_endio() should trace the final completion
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* of this bio. */
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* of this bio. */
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#define BIO_QUEUE_ENTERED 11 /* can use blk_queue_enter_live() */
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/* See BVEC_POOL_OFFSET below before adding new flags */
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/* See BVEC_POOL_OFFSET below before adding new flags */
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/*
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/*
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