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sunrpc: keep a count of swapfiles associated with the rpc_clnt

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Jerome reported seeing a warning pop when working with a swapfile on
NFS. The nfs_swap_activate can end up calling sk_set_memalloc while
holding the rcu_read_lock and that function can sleep.

To fix that, we need to take a reference to the xprt while holding the
rcu_read_lock, set the socket up for swapping and then drop that
reference. But, xprt_put is not exported and having NFS deal with the
underlying xprt is a bit of layering violation anyway.

Fix this by adding a set of activate/deactivate functions that take a
rpc_clnt pointer instead of an rpc_xprt, and have nfs_swap_activate and
nfs_swap_deactivate call those.

Also, add a per-rpc_clnt atomic counter to keep track of the number of
active swapfiles associated with it. When the counter does a 0->1
transition, we enable swapping on the xprt, when we do a 1->0 transition
we disable swapping on it.

This also allows us to be a bit more selective with the RPC_TASK_SWAPPER
flag. If non-swapper and swapper clnts are sharing a xprt, then we only
need to flag the tasks from the swapper clnt with that flag.

Acked-by: Mel Gorman <mgorman@suse.de>
Reported-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Jeff Layton 2015-06-03 16:14:25 -04:00 • committed by Trond Myklebust
parent 0d2a970d0a
commit 3c87ef6efb
5 changed files with 78 additions and 24 deletions
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16
include/linux/sunrpc/sched.h
View file

@ -268,4 +268,20 @@ static inline void rpc_assign_waitqueue_name(struct rpc_wait_queue *q,
}
#endif
#if IS_ENABLED(CONFIG_SUNRPC_SWAP)
int rpc_clnt_swap_activate(struct rpc_clnt *clnt);
void rpc_clnt_swap_deactivate(struct rpc_clnt *clnt);
#else
static inline int
rpc_clnt_swap_activate(struct rpc_clnt *clnt)
{
return -EINVAL;
}
static inline void
rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
{
}
#endif /* CONFIG_SUNRPC_SWAP */
#endif /* _LINUX_SUNRPC_SCHED_H_ */