Re: [RFC v4 5/9] NFS: Kill RPCs for the duration of umount

[NeilBrown <neilb@suse.com>]

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On Fri, Nov 17 2017, Joshua Watt wrote:

> RPCs are now killed for the duration of the umount operation when
> MNT_FORCE is specified. Specifically, if the umount flags are MNT_FORCE
> | MNT_DETACH, all future RPCs will be killed.
>
> Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
> ---
>  fs/nfs/internal.h  |  1 +
>  fs/nfs/nfs4super.c |  1 +
>  fs/nfs/super.c     | 36 +++++++++++++++++++++++++++++-------
>  3 files changed, 31 insertions(+), 7 deletions(-)
>
> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> index f9a4a5524bd5..3ec165368a08 100644
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -461,6 +461,7 @@ extern void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio);
>  
>  /* super.c */
>  void nfs_umount_begin(struct super_block *);
> +void nfs_umount_end(struct super_block *sb);
>  int  nfs_statfs(struct dentry *, struct kstatfs *);
>  int  nfs_show_options(struct seq_file *, struct dentry *);
>  int  nfs_show_devname(struct seq_file *, struct dentry *);
> diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
> index 6fb7cb6b3f4b..e9788f9c3394 100644
> --- a/fs/nfs/nfs4super.c
> +++ b/fs/nfs/nfs4super.c
> @@ -56,6 +56,7 @@ static const struct super_operations nfs4_sops = {
>  	.statfs		= nfs_statfs,
>  	.evict_inode	= nfs4_evict_inode,
>  	.umount_begin	= nfs_umount_begin,
> +	.umount_end	= nfs_umount_end,
>  	.show_options	= nfs_show_options,
>  	.show_devname	= nfs_show_devname,
>  	.show_path	= nfs_show_path,
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index 216f67d628b3..71361ca6d6b4 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -315,6 +315,7 @@ const struct super_operations nfs_sops = {
>  	.statfs		= nfs_statfs,
>  	.evict_inode	= nfs_evict_inode,
>  	.umount_begin	= nfs_umount_begin,
> +	.umount_end	= nfs_umount_end,
>  	.show_options	= nfs_show_options,
>  	.show_devname	= nfs_show_devname,
>  	.show_path	= nfs_show_path,
> @@ -890,6 +891,15 @@ int nfs_show_stats(struct seq_file *m, struct dentry *root)
>  }
>  EXPORT_SYMBOL_GPL(nfs_show_stats);
>  
> +static void
> +kill_rpc(struct rpc_clnt *rpc)
> +{
> +	if (!IS_ERR(rpc)) {
> +		atomic_inc(&rpc->cl_kill_new_tasks);
> +		rpc_killall_tasks(rpc);
> +	}
> +}
> +
>  /*
>   * Begin unmount by attempting to remove all automounted mountpoints we added
>   * in response to xdev traversals and referrals
> @@ -897,19 +907,31 @@ EXPORT_SYMBOL_GPL(nfs_show_stats);
>  void nfs_umount_begin(struct super_block *sb)
>  {
>  	struct nfs_server *server;
> -	struct rpc_clnt *rpc;
>  
>  	server = NFS_SB(sb);
>  	/* -EIO all pending I/O */
> -	rpc = server->client_acl;
> -	if (!IS_ERR(rpc))
> -		rpc_killall_tasks(rpc);
> -	rpc = server->client;
> -	if (!IS_ERR(rpc))
> -		rpc_killall_tasks(rpc);
> +	kill_rpc(server->client_acl);
> +	kill_rpc(server->client);
>  }
>  EXPORT_SYMBOL_GPL(nfs_umount_begin);
>  
> +static void
> +restore_rpc(struct rpc_clnt *rpc)
> +{
> +	if (!IS_ERR(rpc))
> +		__atomic_add_unless(&rpc->cl_kill_new_tasks, -1, 0);

Why use __atomic_add_unless() instead of the more obvious
atomic_add_unless()?
The only difference is the return value and as you ignore that, it isn't
a difference.

Thanks,
NeilBrown


> +}
> +
> +void
> +nfs_umount_end(struct super_block *sb)
> +{
> +	struct nfs_server *server = NFS_SB(sb);
> +
> +	restore_rpc(server->client_acl);
> +	restore_rpc(server->client);
> +}
> +EXPORT_SYMBOL_GPL(nfs_umount_end);
> +
>  static struct nfs_parsed_mount_data *nfs_alloc_parsed_mount_data(void)
>  {
>  	struct nfs_parsed_mount_data *data;
> -- 
> 2.13.6
>
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