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nbd: don't handle response without a corresponding request message

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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>
This commit is contained in:
Yu Kuai 2021-09-16 17:33:44 +08:00 committed by Jens Axboe
parent c573d58699
commit 4e6eef5dc2
1 changed files with 21 additions and 1 deletions
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22
drivers/block/nbd.c
View file

@ -131,6 +131,12 @@ struct nbd_device {
};
#define NBD_CMD_REQUEUED 1
/*
* This flag will be set if nbd_queue_rq() succeed, and will be checked and
* cleared in completion. Both setting and clearing of the flag are protected
* by cmd->lock.
*/
#define NBD_CMD_INFLIGHT 2
struct nbd_cmd {
struct nbd_device *nbd;
@ -405,6 +411,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
if (!mutex_trylock(&cmd->lock))
return BLK_EH_RESET_TIMER;
__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
if (!refcount_inc_not_zero(&nbd->config_refs)) {
cmd->status = BLK_STS_TIMEOUT;
mutex_unlock(&cmd->lock);
@ -734,6 +741,12 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
cmd = blk_mq_rq_to_pdu(req);
mutex_lock(&cmd->lock);
if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
dev_err(disk_to_dev(nbd->disk), "Suspicious reply %d (status %u flags %lu)",
tag, cmd->status, cmd->flags);
ret = -ENOENT;
goto out;
}
if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) {
dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n",
req, cmd->cmd_cookie, nbd_handle_to_cookie(handle));
@ -833,6 +846,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved)
return true;
mutex_lock(&cmd->lock);
__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
cmd->status = BLK_STS_IOERR;
mutex_unlock(&cmd->lock);
@ -969,7 +983,13 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
* returns EAGAIN can be retried on a different socket.
*/
ret = nbd_send_cmd(nbd, cmd, index);
if (ret == -EAGAIN) {
/*
* Access to this flag is protected by cmd->lock, thus it's safe to set
* the flag after nbd_send_cmd() succeed to send request to server.
*/
if (!ret)
__set_bit(NBD_CMD_INFLIGHT, &cmd->flags);
else if (ret == -EAGAIN) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Request send failed, requeueing\n");
nbd_mark_nsock_dead(nbd, nsock, 1);