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nvme-mpath: fix I/O failure with EAGAIN when failing over I/O

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It is possible that the next available path we failover to, happens to
be frozen (for example if it is during connection establishment). If
the original I/O was set with NOWAIT, this cause the I/O to unnecessarily
fail because the request queue cannot be entered, hence the I/O fails with
EAGAIN.

The NOWAIT restriction that was originally set for the I/O is no longer
relevant or needed because this is the nvme requeue context. Hence we
clear the REQ_NOWAIT flag when failing over I/O.

This fix a simple test case of nvme controller reset during I/O when the
multipath device that has only a single path and I/O fails with "Resource
temporarily unavailable" errno. Note that this reproduces with io_uring
which by default sets IOCB_NOWAIT by default.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
This commit is contained in:
Sagi Grimberg 2023-06-20 16:07:36 +03:00 committed by Keith Busch
parent 86da1bae4c
commit 99160af413
1 changed files with 8 additions and 0 deletions
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8
drivers/nvme/host/multipath.c
View file

@ -106,6 +106,14 @@ void nvme_failover_req(struct request *req)
bio->bi_opf &= ~REQ_POLLED;
bio->bi_cookie = BLK_QC_T_NONE;
}
/*
* The alternate request queue that we may end up submitting
* the bio to may be frozen temporarily, in this case REQ_NOWAIT
* will fail the I/O immediately with EAGAIN to the issuer.
* We are not in the issuer context which cannot block. Clear
* the flag to avoid spurious EAGAIN I/O failures.
*/
bio->bi_opf &= ~REQ_NOWAIT;
}
blk_steal_bios(&ns->head->requeue_list, req);
spin_unlock_irqrestore(&ns->head->requeue_lock, flags);