nfsd: implement pNFS layout recalls

Add support to issue layout recalls to clients.  For now we only support
full-file recalls to get a simple and stable implementation.  This allows
to embedd a nfsd4_callback structure in the layout_state and thus avoid
any memory allocations under spinlocks during a recall.  For normal
use cases that do not intent to share a single file between multiple
clients this implementation is fully sufficient.

To ensure layouts are recalled on local filesystem access each layout
state registers a new FL_LAYOUT lease with the kernel file locking code,
which filesystems that support pNFS exports that require recalls need
to break on conflicting access patterns.

The XDR code is based on the old pNFS server implementation by
Andy Adamson, Benny Halevy, Boaz Harrosh, Dean Hildebrand, Fred Isaman,
Marc Eshel, Mike Sager and Ricardo Labiaga.

Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 5f66b7f..4f3bfeb 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -502,6 +502,7 @@ struct nfs4_file {
 	bool			fi_had_conflict;
 #ifdef CONFIG_NFSD_PNFS
 	struct list_head	fi_lo_states;
+	atomic_t		fi_lo_recalls;
 #endif
 };
 
@@ -542,6 +543,10 @@ struct nfs4_layout_stateid {
 	spinlock_t			ls_lock;
 	struct list_head		ls_layouts;
 	u32				ls_layout_type;
+	struct file			*ls_file;
+	struct nfsd4_callback		ls_recall;
+	stateid_t			ls_recall_sid;
+	bool				ls_recalled;
 };
 
 static inline struct nfs4_layout_stateid *layoutstateid(struct nfs4_stid *s)
@@ -556,6 +561,7 @@ static inline struct nfs4_layout_stateid *layoutstateid(struct nfs4_stid *s)
 enum nfsd4_cb_op {
 	NFSPROC4_CLNT_CB_NULL = 0,
 	NFSPROC4_CLNT_CB_RECALL,
+	NFSPROC4_CLNT_CB_LAYOUT,
 	NFSPROC4_CLNT_CB_SEQUENCE,
 };