xen-blkfront: fix double completion of split requests on resume#7
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xen-blkfront: fix double completion of split requests on resume#7blktests-ci-block-trial[bot] wants to merge 1 commit into
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When a block request is too large for a single ring entry and the backend does not support indirect descriptors, blkfront splits it across two ring requests. This only happens when the frontend runs on a 64K-page kernel (e.g. arm64): there, even a single-page request may not fit in one ring slot and must be split. blkif_ring_get_request() is called twice and both shadow slots (shadow[id] and shadow[extra_id]) point at the *same* struct request, linked through associated_id. blkif_completion() collapses the pair on the normal completion path, recycling the second slot and completing the request once. The suspend/resume walk in blkfront_resume() does not: it visits every shadow slot with ->request set and calls blk_mq_end_request() or re-queues ->request. For an in-flight split request it therefore processes the shared struct request twice on resume/migration -- a double completion. Skip the secondary slot of a split request in the resume walk so each logical request is processed exactly once. The secondary slot is the linked one (associated_id != NO_ASSOCIATED_ID) that carries no scatter-gather list (num_sg == 0); the first slot always keeps the sg list. The bug is only reachable on suspend/resume or live migration of such a guest, so it has no local reproducer. Fixes: 6cc5683 ("xen/blkfront: Handle non-indirect grant with 64KB pages") Assisted-by: 0sec:claude-opus-4-8 Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
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Upstream branch: a635d67 |
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Pull request for series with
subject: xen-blkfront: fix double completion of split requests on resume
version: 2
url: http://redsun45:8000/project/linux-block/list/?series=276