pnfs: layoutret_on_setattr

With the objects layout security model, we have object capabilities
that are associated with the layout and we anticipate that the server
will issue a cb_layoutrecall for any setattr that changes security
related attributes (user/group/mode/acl) or truncates the file.

Therefore, the layout is returned before issuing the setattr to avoid
the anticipated cb_layoutrecall.
Signed-off-by: Benny Halevy <bhalevy@panasas.com>

fs/nfs/nfs4proc.c

@@ -2361,6 +2361,9 @@ nfs4_proc_setattr(struct dentry *dentry, struct nfs_fattr *fattr,
 	struct nfs4_state *state = NULL;
 	int status;
 
+	if (pnfs_ld_layoutret_on_setattr(inode))
+		pnfs_return_layout(inode);
+
 	nfs_fattr_init(fattr);
 	
 	/* Search for an existing open(O_WRITE) file */

fs/nfs/objlayout/objio_osd.c

@@ -964,6 +964,7 @@ objlayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 static struct pnfs_layoutdriver_type objlayout_type = {
 	.id = LAYOUT_OSD2_OBJECTS,
 	.name = "LAYOUT_OSD2_OBJECTS",
+	.flags                   = PNFS_LAYOUTRET_ON_SETATTR,
 
 	.alloc_layout_hdr        = objlayout_alloc_layout_hdr,
 	.free_layout_hdr         = objlayout_free_layout_hdr,

fs/nfs/pnfs.h

@@ -65,6 +65,11 @@ enum {
 	NFS_LAYOUT_DESTROYED,		/* no new use of layout allowed */
 };
 
+enum layoutdriver_policy_flags {
+	/* Should the pNFS client commit and return the layout upon a setattr */
+	PNFS_LAYOUTRET_ON_SETATTR	= 1 << 0,
+};
+
 struct nfs4_deviceid_node;
 
 /* Per-layout driver specific registration structure */
@@ -73,6 +78,7 @@ struct pnfs_layoutdriver_type {
 	const u32 id;
 	const char *name;
 	struct module *owner;
+	unsigned flags;
 
 	struct pnfs_layout_hdr * (*alloc_layout_hdr) (struct inode *inode, gfp_t gfp_flags);
 	void (*free_layout_hdr) (struct pnfs_layout_hdr *);
@@ -258,6 +264,16 @@ static inline void pnfs_clear_request_commit(struct nfs_page *req)
 		put_lseg(req->wb_commit_lseg);
 }
 
+/* Should the pNFS client commit and return the layout upon a setattr */
+static inline bool
+pnfs_ld_layoutret_on_setattr(struct inode *inode)
+{
+	if (!pnfs_enabled_sb(NFS_SERVER(inode)))
+		return false;
+	return NFS_SERVER(inode)->pnfs_curr_ld->flags &
+		PNFS_LAYOUTRET_ON_SETATTR;
+}
+
 static inline int pnfs_return_layout(struct inode *ino)
 {
 	struct nfs_inode *nfsi = NFS_I(ino);
@@ -316,6 +332,12 @@ static inline int pnfs_return_layout(struct inode *ino)
 	return 0;
 }
 
+static inline bool
+pnfs_ld_layoutret_on_setattr(struct inode *inode)
+{
+	return false;
+}
+
 static inline bool
 pnfs_roc(struct inode *ino)
 {