Avoid completing I/O when dumping core after a panic.
Filesystem or pager completion callbacks are generally non-functional after a panic and may trigger deadlocks if invoked in this context (e.g., by attempting to destroying a buffer mapping). To avoid this situation, short-circuit I/O completion in biodone(). Reviewed by: imp Discussed with: mav MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D15592
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=334506
@ -4310,6 +4310,8 @@ allocbuf(struct buf *bp, int size)
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extern int inflight_transient_maps;
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static struct bio_queue nondump_bios;
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void
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biodone(struct bio *bp)
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{
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@ -4318,6 +4320,17 @@ biodone(struct bio *bp)
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vm_offset_t start, end;
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biotrack(bp, __func__);
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/*
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* Avoid completing I/O when dumping after a panic since that may
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* result in a deadlock in the filesystem or pager code. Note that
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* this doesn't affect dumps that were started manually since we aim
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* to keep the system usable after it has been resumed.
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*/
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if (__predict_false(dumping && SCHEDULER_STOPPED())) {
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TAILQ_INSERT_HEAD(&nondump_bios, bp, bio_queue);
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return;
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}
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if ((bp->bio_flags & BIO_TRANSIENT_MAPPING) != 0) {
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bp->bio_flags &= ~BIO_TRANSIENT_MAPPING;
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bp->bio_flags |= BIO_UNMAPPED;
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