On Mon, Jun 30, 2014 at 11:48:33AM -0400, Jeff Layton wrote:
> state_lock is a heavily contended global lock. We don't want to grab
> that while simultaneously holding the inode->i_lock.
>
> Add a new per-nfs4_file lock that we can use to protect the
> per-nfs4_file delegation list. Hold that while walking the list in the
> break_deleg callback and queue the workqueue job for each one.
>
> The workqueue job can then take the state_lock and do the list
> manipulations without the i_lock being held prior to starting the
> rpc call.
The code tends to assume that the callback thread only works with the
delegation struct itself and puts it when done but doesn't otherwise
touch other state.
I wonder how this interacts with state shutdown....
E.g. in nfs4_state_shutdown_net() we walk the dl_recall_lru and destroy
everything we find, but this callback workqueue is still running so I
think another delegation could get added to that list after this? Does
that cause bugs?
And it'd also be worth checking delegreturn and destroy_client.
Maybe there's no bug, or they just need to flush the workqueue at the
appropriate point.
There's also a preexisting expire_client/laundromat vs break race:
- expire_client/laundromat adds a delegation to its local
reaplist using the same dl_recall_lru field that a delegation
uses to track its position on the recall lru and drops the
state lock.
- a concurrent break_lease adds the delegation to the lru.
- expire/client/laundromat then walks it reaplist and sees the
lru head as just another delegation on the list....
Possibly unrelated, but it might be good to fix that first.
--b.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/nfsd/nfs4callback.c | 28 +++++++++++++++++++++-------
> fs/nfsd/nfs4state.c | 43 ++++++++++++++++++++++++++++---------------
> fs/nfsd/state.h | 2 ++
> 3 files changed, 51 insertions(+), 22 deletions(-)
>
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 00cb9b7a75f6..cba4ca375f5e 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -43,7 +43,7 @@
> #define NFSDDBG_FACILITY NFSDDBG_PROC
>
> static void nfsd4_mark_cb_fault(struct nfs4_client *, int reason);
> -static void nfsd4_do_callback_rpc(struct work_struct *w);
> +static void nfsd4_run_cb_null(struct work_struct *w);
>
> #define NFSPROC4_CB_NULL 0
> #define NFSPROC4_CB_COMPOUND 1
> @@ -764,7 +764,7 @@ static void do_probe_callback(struct nfs4_client *clp)
>
> cb->cb_ops = &nfsd4_cb_probe_ops;
>
> - INIT_WORK(&cb->cb_work, nfsd4_do_callback_rpc);
> + INIT_WORK(&cb->cb_work, nfsd4_run_cb_null);
>
> run_nfsd4_cb(cb);
> }
> @@ -936,7 +936,7 @@ void nfsd4_shutdown_callback(struct nfs4_client *clp)
> set_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags);
> /*
> * Note this won't actually result in a null callback;
> - * instead, nfsd4_do_callback_rpc() will detect the killed
> + * instead, nfsd4_run_cb_null() will detect the killed
> * client, destroy the rpc client, and stop:
> */
> do_probe_callback(clp);
> @@ -1014,9 +1014,8 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
> run_nfsd4_cb(cb);
> }
>
> -static void nfsd4_do_callback_rpc(struct work_struct *w)
> +static void nfsd4_run_callback_rpc(struct nfsd4_callback *cb)
> {
> - struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, cb_work);
> struct nfs4_client *clp = cb->cb_clp;
> struct rpc_clnt *clnt;
>
> @@ -1034,6 +1033,22 @@ static void nfsd4_do_callback_rpc(struct work_struct *w)
> cb->cb_ops, cb);
> }
>
> +static void nfsd4_run_cb_null(struct work_struct *w)
> +{
> + struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback,
> + cb_work);
> + nfsd4_run_callback_rpc(cb);
> +}
> +
> +static void nfsd4_run_cb_recall(struct work_struct *w)
> +{
> + struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback,
> + cb_work);
> +
> + nfsd4_prepare_cb_recall(cb->cb_op);
> + nfsd4_run_callback_rpc(cb);
> +}
> +
> void nfsd4_cb_recall(struct nfs4_delegation *dp)
> {
> struct nfsd4_callback *cb = &dp->dl_recall;
> @@ -1050,8 +1065,7 @@ void nfsd4_cb_recall(struct nfs4_delegation *dp)
>
> INIT_LIST_HEAD(&cb->cb_per_client);
> cb->cb_done = true;
> -
> - INIT_WORK(&cb->cb_work, nfsd4_do_callback_rpc);
> + INIT_WORK(&cb->cb_work, nfsd4_run_cb_recall);
>
> run_nfsd4_cb(&dp->dl_recall);
> }
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index b49b46b0ce23..461229a01963 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -513,7 +513,9 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
> lockdep_assert_held(&state_lock);
>
> dp->dl_stid.sc_type = NFS4_DELEG_STID;
> + spin_lock(&fp->fi_lock);
> list_add(&dp->dl_perfile, &fp->fi_delegations);
> + spin_unlock(&fp->fi_lock);
> list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
> }
>
> @@ -521,14 +523,18 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
> static void
> unhash_delegation(struct nfs4_delegation *dp)
> {
> + struct nfs4_file *fp = dp->dl_file;
> +
> spin_lock(&state_lock);
> list_del_init(&dp->dl_perclnt);
> - list_del_init(&dp->dl_perfile);
> list_del_init(&dp->dl_recall_lru);
> + spin_lock(&fp->fi_lock);
> + list_del_init(&dp->dl_perfile);
> + spin_unlock(&fp->fi_lock);
> spin_unlock(&state_lock);
> - if (dp->dl_file) {
> - nfs4_put_deleg_lease(dp->dl_file);
> - put_nfs4_file(dp->dl_file);
> + if (fp) {
> + nfs4_put_deleg_lease(fp);
> + put_nfs4_file(fp);
> dp->dl_file = NULL;
> }
> }
> @@ -2612,6 +2618,7 @@ static void nfsd4_init_file(struct nfs4_file *fp, struct inode *ino)
> lockdep_assert_held(&state_lock);
>
> atomic_set(&fp->fi_ref, 1);
> + spin_lock_init(&fp->fi_lock);
> INIT_LIST_HEAD(&fp->fi_stateids);
> INIT_LIST_HEAD(&fp->fi_delegations);
> ihold(ino);
> @@ -2857,26 +2864,32 @@ out:
> return ret;
> }
>
> -static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
> +void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp)
> {
> struct nfs4_client *clp = dp->dl_stid.sc_client;
> struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
>
> - lockdep_assert_held(&state_lock);
> + /*
> + * We can't do this in nfsd_break_deleg_cb because it is
> + * already holding inode->i_lock
> + */
> + spin_lock(&state_lock);
> + if (list_empty(&dp->dl_recall_lru)) {
> + dp->dl_time = get_seconds();
> + list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);
> + }
> + spin_unlock(&state_lock);
> +}
> +
> +static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
> +{
> /* We're assuming the state code never drops its reference
> * without first removing the lease. Since we're in this lease
> * callback (and since the lease code is serialized by the kernel
> * lock) we know the server hasn't removed the lease yet, we know
> * it's safe to take a reference: */
> atomic_inc(&dp->dl_count);
> -
> - list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);
> -
> - /* Only place dl_time is set; protected by i_lock: */
> - dp->dl_time = get_seconds();
> -
> block_delegations(&dp->dl_fh);
> -
> nfsd4_cb_recall(dp);
> }
>
> @@ -2901,11 +2914,11 @@ static void nfsd_break_deleg_cb(struct file_lock *fl)
> */
> fl->fl_break_time = 0;
>
> - spin_lock(&state_lock);
> fp->fi_had_conflict = true;
> + spin_lock(&fp->fi_lock);
> list_for_each_entry(dp, &fp->fi_delegations, dl_perfile)
> nfsd_break_one_deleg(dp);
> - spin_unlock(&state_lock);
> + spin_unlock(&fp->fi_lock);
> }
>
> static
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 9447f86f2778..7d6ba06c1abe 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -382,6 +382,7 @@ static inline struct nfs4_lockowner * lockowner(struct nfs4_stateowner *so)
> /* nfs4_file: a file opened by some number of (open) nfs4_stateowners. */
> struct nfs4_file {
> atomic_t fi_ref;
> + spinlock_t fi_lock;
> struct hlist_node fi_hash; /* hash by "struct inode *" */
> struct list_head fi_stateids;
> struct list_head fi_delegations;
> @@ -471,6 +472,7 @@ extern void nfsd4_cb_recall(struct nfs4_delegation *dp);
> extern int nfsd4_create_callback_queue(void);
> extern void nfsd4_destroy_callback_queue(void);
> extern void nfsd4_shutdown_callback(struct nfs4_client *);
> +extern void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp);
> extern void nfs4_put_delegation(struct nfs4_delegation *dp);
> extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(const char *name,
> struct nfsd_net *nn);
> --
> 1.9.3
>
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