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nbd: don't handle response without a corresponding request message
While handling a response message from server, nbd_read_stat() will try to get request by tag, and then complete the request. However, this is problematic if nbd haven't sent a corresponding request message: t1 t2 submit_bio nbd_queue_rq blk_mq_start_request recv_work nbd_read_stat blk_mq_tag_to_rq blk_mq_complete_request nbd_send_cmd Thus add a new cmd flag 'NBD_CMD_INFLIGHT', it will be set in nbd_send_cmd() and checked in nbd_read_stat(). Noted that this patch can't fix that blk_mq_tag_to_rq() might return a freed request, and this will be fixed in following patches. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-2-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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1 changed files with 21 additions and 1 deletions
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@ -131,6 +131,12 @@ struct nbd_device {
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};
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#define NBD_CMD_REQUEUED 1
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/*
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* This flag will be set if nbd_queue_rq() succeed, and will be checked and
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* cleared in completion. Both setting and clearing of the flag are protected
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* by cmd->lock.
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*/
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#define NBD_CMD_INFLIGHT 2
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struct nbd_cmd {
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struct nbd_device *nbd;
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@ -405,6 +411,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
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if (!mutex_trylock(&cmd->lock))
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return BLK_EH_RESET_TIMER;
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__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
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if (!refcount_inc_not_zero(&nbd->config_refs)) {
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cmd->status = BLK_STS_TIMEOUT;
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mutex_unlock(&cmd->lock);
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@ -734,6 +741,12 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
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cmd = blk_mq_rq_to_pdu(req);
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mutex_lock(&cmd->lock);
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if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
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dev_err(disk_to_dev(nbd->disk), "Suspicious reply %d (status %u flags %lu)",
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tag, cmd->status, cmd->flags);
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ret = -ENOENT;
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goto out;
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}
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if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) {
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dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n",
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req, cmd->cmd_cookie, nbd_handle_to_cookie(handle));
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@ -833,6 +846,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved)
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return true;
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mutex_lock(&cmd->lock);
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__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
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cmd->status = BLK_STS_IOERR;
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mutex_unlock(&cmd->lock);
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@ -969,7 +983,13 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
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* returns EAGAIN can be retried on a different socket.
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*/
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ret = nbd_send_cmd(nbd, cmd, index);
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if (ret == -EAGAIN) {
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/*
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* Access to this flag is protected by cmd->lock, thus it's safe to set
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* the flag after nbd_send_cmd() succeed to send request to server.
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*/
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if (!ret)
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__set_bit(NBD_CMD_INFLIGHT, &cmd->flags);
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else if (ret == -EAGAIN) {
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dev_err_ratelimited(disk_to_dev(nbd->disk),
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"Request send failed, requeueing\n");
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nbd_mark_nsock_dead(nbd, nsock, 1);
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