Re: [PATCH 2/2] nfs: move the nfs4_data_server_cache into struct nfs_net

[Anna Schumaker <anna.schumaker@oracle.com>]

Hi Jeff,

On 4/10/25 2:12 PM, Jeff Layton wrote:
> Since struct nfs4_pnfs_ds should not be shared between net namespaces,
> move from a global list of objects to a per-netns list and spinlock.
> 
> Tested-by: Sargun Dillon <sargun@sargun.me>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/nfs/client.c   |  4 ++++
>  fs/nfs/inode.c    |  3 +++
>  fs/nfs/netns.h    |  6 +++++-
>  fs/nfs/pnfs_nfs.c | 31 +++++++++++++++++--------------
>  4 files changed, 29 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 9500b46005b0148a5a9a7d464095ca944de06bb5..81c0f780ff82c8a020fafdb3df72552c8e6e535f 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -1199,6 +1199,10 @@ void nfs_clients_init(struct net *net)
>  	INIT_LIST_HEAD(&nn->nfs_volume_list);
>  #if IS_ENABLED(CONFIG_NFS_V4)
>  	idr_init(&nn->cb_ident_idr);
> +#if IS_ENABLED(CONFIG_NFS_V4_1)
> +	INIT_LIST_HEAD(&nn->nfs4_data_server_cache);
> +	spin_lock_init(&nn->nfs4_data_server_lock);
> +#endif
>  #endif
>  	spin_lock_init(&nn->nfs_client_lock);
>  	nn->boot_time = ktime_get_real();
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index 119e447758b994b34e55e7b28fd4f34fa089e2e1..ee796a726a1e4b0dfbd199cc62176c6802692671 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -2559,6 +2559,9 @@ static int nfs_net_init(struct net *net)
>  
>  static void nfs_net_exit(struct net *net)
>  {
> +	struct nfs_net *nn = net_generic(net, nfs_net_id);
> +
> +	WARN_ON_ONCE(!list_empty(&nn->nfs4_data_server_cache));

nfs4_data_server_cache is defined under an #if IS_ENABLED(CONFIG_NFS_V4_1) block,
so the compiler complains if this isn't enabled:

fs/nfs/inode.c:2564:32: error: no member named 'nfs4_data_server_cache' in 'struct nfs_net'
 2564 |         WARN_ON_ONCE(!list_empty(&nn->nfs4_data_server_cache));

Anna

>  	rpc_proc_unregister(net, "nfs");
>  	nfs_fs_proc_net_exit(net);
>  	nfs_clients_exit(net);
> diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h
> index a68b21603ea9a867ba513e2a667b08fbc6d80dd8..557cf822002663b7957194610d103210b159e5c4 100644
> --- a/fs/nfs/netns.h
> +++ b/fs/nfs/netns.h
> @@ -31,7 +31,11 @@ struct nfs_net {
>  	unsigned short nfs_callback_tcpport;
>  	unsigned short nfs_callback_tcpport6;
>  	int cb_users[NFS4_MAX_MINOR_VERSION + 1];
> -#endif
> +#if IS_ENABLED(CONFIG_NFS_V4_1)
> +	struct list_head nfs4_data_server_cache;
> +	spinlock_t nfs4_data_server_lock;
> +#endif /* CONFIG_NFS_V4_1 */
> +#endif /* CONFIG_NFS_V4 */
>  	struct nfs_netns_client *nfs_client;
>  	spinlock_t nfs_client_lock;
>  	ktime_t boot_time;
> diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
> index 2ee20a0f0b36d3b38e35c4cad966b9d58fa822f4..91ef486f40b943a1dc55164e610378ef73781e55 100644
> --- a/fs/nfs/pnfs_nfs.c
> +++ b/fs/nfs/pnfs_nfs.c
> @@ -16,6 +16,7 @@
>  #include "nfs4session.h"
>  #include "internal.h"
>  #include "pnfs.h"
> +#include "netns.h"
>  
>  #define NFSDBG_FACILITY		NFSDBG_PNFS
>  
> @@ -504,14 +505,14 @@ EXPORT_SYMBOL_GPL(pnfs_generic_commit_pagelist);
>  /*
>   * Data server cache
>   *
> - * Data servers can be mapped to different device ids.
> - * nfs4_pnfs_ds reference counting
> + * Data servers can be mapped to different device ids, but should
> + * never be shared between net namespaces.
> + *
> + * nfs4_pnfs_ds reference counting:
>   *   - set to 1 on allocation
>   *   - incremented when a device id maps a data server already in the cache.
>   *   - decremented when deviceid is removed from the cache.
>   */
> -static DEFINE_SPINLOCK(nfs4_ds_cache_lock);
> -static LIST_HEAD(nfs4_data_server_cache);
>  
>  /* Debug routines */
>  static void
> @@ -604,12 +605,12 @@ _same_data_server_addrs_locked(const struct list_head *dsaddrs1,
>   * Lookup DS by addresses.  nfs4_ds_cache_lock is held
>   */
>  static struct nfs4_pnfs_ds *
> -_data_server_lookup_locked(const struct net *net, const struct list_head *dsaddrs)
> +_data_server_lookup_locked(const struct nfs_net *nn, const struct list_head *dsaddrs)
>  {
>  	struct nfs4_pnfs_ds *ds;
>  
> -	list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
> -		if (ds->ds_net == net && _same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
> +	list_for_each_entry(ds, &nn->nfs4_data_server_cache, ds_node)
> +		if (_same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
>  			return ds;
>  	return NULL;
>  }
> @@ -653,10 +654,11 @@ static void destroy_ds(struct nfs4_pnfs_ds *ds)
>  
>  void nfs4_pnfs_ds_put(struct nfs4_pnfs_ds *ds)
>  {
> -	if (refcount_dec_and_lock(&ds->ds_count,
> -				&nfs4_ds_cache_lock)) {
> +	struct nfs_net *nn = net_generic(ds->ds_net, nfs_net_id);
> +
> +	if (refcount_dec_and_lock(&ds->ds_count, &nn->nfs4_data_server_lock)) {
>  		list_del_init(&ds->ds_node);
> -		spin_unlock(&nfs4_ds_cache_lock);
> +		spin_unlock(&nn->nfs4_data_server_lock);
>  		destroy_ds(ds);
>  	}
>  }
> @@ -718,6 +720,7 @@ nfs4_pnfs_remotestr(struct list_head *dsaddrs, gfp_t gfp_flags)
>  struct nfs4_pnfs_ds *
>  nfs4_pnfs_ds_add(const struct net *net, struct list_head *dsaddrs, gfp_t gfp_flags)
>  {
> +	struct nfs_net *nn = net_generic(net, nfs_net_id);
>  	struct nfs4_pnfs_ds *tmp_ds, *ds = NULL;
>  	char *remotestr;
>  
> @@ -733,8 +736,8 @@ nfs4_pnfs_ds_add(const struct net *net, struct list_head *dsaddrs, gfp_t gfp_fla
>  	/* this is only used for debugging, so it's ok if its NULL */
>  	remotestr = nfs4_pnfs_remotestr(dsaddrs, gfp_flags);
>  
> -	spin_lock(&nfs4_ds_cache_lock);
> -	tmp_ds = _data_server_lookup_locked(net, dsaddrs);
> +	spin_lock(&nn->nfs4_data_server_lock);
> +	tmp_ds = _data_server_lookup_locked(nn, dsaddrs);
>  	if (tmp_ds == NULL) {
>  		INIT_LIST_HEAD(&ds->ds_addrs);
>  		list_splice_init(dsaddrs, &ds->ds_addrs);
> @@ -743,7 +746,7 @@ nfs4_pnfs_ds_add(const struct net *net, struct list_head *dsaddrs, gfp_t gfp_fla
>  		INIT_LIST_HEAD(&ds->ds_node);
>  		ds->ds_net = net;
>  		ds->ds_clp = NULL;
> -		list_add(&ds->ds_node, &nfs4_data_server_cache);
> +		list_add(&ds->ds_node, &nn->nfs4_data_server_cache);
>  		dprintk("%s add new data server %s\n", __func__,
>  			ds->ds_remotestr);
>  	} else {
> @@ -755,7 +758,7 @@ nfs4_pnfs_ds_add(const struct net *net, struct list_head *dsaddrs, gfp_t gfp_fla
>  			refcount_read(&tmp_ds->ds_count));
>  		ds = tmp_ds;
>  	}
> -	spin_unlock(&nfs4_ds_cache_lock);
> +	spin_unlock(&nn->nfs4_data_server_lock);
>  out:
>  	return ds;
>  }
>