[PATCH AUTOSEL 4.19 36/38] nbd: protect cmd->status with cmd->lock

Sasha Levin
2019-10-30T15:55:52Z

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 bc2fa4e85f0ca..46cd52d1d6537 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