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    Subject[PATCH 4.19 35/79] nbd: protect cmd->status with cmd->lock
    Date
    From: Josef Bacik <josef@toxicpanda.com>

    [ Upstream commit de6346ecbc8f5591ebd6c44ac164e8b8671d71d7 ]

    We already do this for the most part, except in timeout and clear_req.
    For the timeout case we take the lock after we grab a ref on the config,
    but that isn't really necessary because we're safe to touch the cmd at
    this point, so just move the order around.

    For the clear_req cause this is initiated by the user, so again is safe.

    Reviewed-by: Mike Christie <mchristi@redhat.com>
    Signed-off-by: Josef Bacik <josef@toxicpanda.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/block/nbd.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
    index bd9aafe86c2fc..da6a36d14f4cf 100644
    --- a/drivers/block/nbd.c
    +++ b/drivers/block/nbd.c
    @@ -349,17 +349,16 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
    struct nbd_device *nbd = cmd->nbd;
    struct nbd_config *config;

    + if (!mutex_trylock(&cmd->lock))
    + return BLK_EH_RESET_TIMER;
    +
    if (!refcount_inc_not_zero(&nbd->config_refs)) {
    cmd->status = BLK_STS_TIMEOUT;
    + mutex_unlock(&cmd->lock);
    goto done;
    }
    config = nbd->config;

    - if (!mutex_trylock(&cmd->lock)) {
    - nbd_config_put(nbd);
    - return BLK_EH_RESET_TIMER;
    - }
    -
    if (config->num_connections > 1) {
    dev_err_ratelimited(nbd_to_dev(nbd),
    "Connection timed out, retrying (%d/%d alive)\n",
    @@ -745,7 +744,10 @@ static void nbd_clear_req(struct request *req, void *data, bool reserved)
    {
    struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);

    + mutex_lock(&cmd->lock);
    cmd->status = BLK_STS_IOERR;
    + mutex_unlock(&cmd->lock);
    +
    blk_mq_complete_request(req);
    }

    --
    2.20.1


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