NFS: Define and create superblock-level objects

Define and create superblock-level cache index objects (as managed by
nfs_server structs).

Each superblock object is created in a server level index object and is itself
an index into which inode-level objects are inserted.

Ideally there would be one superblock-level object per server, and the former
would be folded into the latter; however, since the "nosharecache" option
exists this isn't possible.

The superblock object key is a sequence consisting of:

 (1) Certain superblock s_flags.

 (2) Various connection parameters that serve to distinguish superblocks for
     sget().

 (3) The volume FSID.

 (4) The security flavour.

 (5) The uniquifier length.

 (6) The uniquifier text.  This is normally an empty string, unless the fsc=xyz
     mount option was used to explicitly specify a uniquifier.

The key blob is of variable length, depending on the length of (6).

The superblock object is given no coherency data to carry in the auxiliary data
permitted by the cache.  It is assumed that the superblock is always coherent.

This patch also adds uniquification handling such that two otherwise identical
superblocks, at least one of which is marked "nosharecache", won't end up
trying to share the on-disk cache.  It will be possible to manually provide a
uniquifier through a mount option with a later patch to avoid the error
otherwise produced.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/fs/nfs/fscache.h b/fs/nfs/fscache.h
index 1d864bedf154..22b971e8b380 100644
--- a/fs/nfs/fscache.h
+++ b/fs/nfs/fscache.h
@@ -20,10 +20,48 @@
 #ifdef CONFIG_NFS_FSCACHE
 
 /*
+ * set of NFS FS-Cache objects that form a superblock key
+ */
+struct nfs_fscache_key {
+        struct rb_node          node;
+        struct nfs_client       *nfs_client;    /* the server */
+
+        /* the elements of the unique key - as used by nfs_compare_super() and
+         * nfs_compare_mount_options() to distinguish superblocks */
+        struct {
+                struct {
+                        unsigned long   s_flags;        /* various flags
+                                                         * (& NFS_MS_MASK) */
+                } super;
+
+                struct {
+                        struct nfs_fsid fsid;
+                        int             flags;
+                        unsigned int    rsize;          /* read size */
+                        unsigned int    wsize;          /* write size */
+                        unsigned int    acregmin;       /* attr cache timeouts */
+                        unsigned int    acregmax;
+                        unsigned int    acdirmin;
+                        unsigned int    acdirmax;
+                } nfs_server;
+
+                struct {
+                        rpc_authflavor_t au_flavor;
+                } rpc_auth;
+
+                /* uniquifier - can be used if nfs_server.flags includes
+                 * NFS_MOUNT_UNSHARED  */
+                u8 uniq_len;
+                char uniquifier[0];
+        } key;
+};
+
+/*
  * fscache-index.c
  */
 extern struct fscache_netfs nfs_fscache_netfs;
 extern const struct fscache_cookie_def nfs_fscache_server_index_def;
+extern const struct fscache_cookie_def nfs_fscache_super_index_def;
 
 extern int nfs_fscache_register(void);
 extern void nfs_fscache_unregister(void);
@@ -34,6 +72,10 @@ extern void nfs_fscache_unregister(void);
 extern void nfs_fscache_get_client_cookie(struct nfs_client *);
 extern void nfs_fscache_release_client_cookie(struct nfs_client *);
 
+extern void nfs_fscache_get_super_cookie(struct super_block *,
+                                         struct nfs_parsed_mount_data *);
+extern void nfs_fscache_release_super_cookie(struct super_block *);
+
 #else /* CONFIG_NFS_FSCACHE */
 static inline int nfs_fscache_register(void) { return 0; }
 static inline void nfs_fscache_unregister(void) {}
@@ -41,5 +83,12 @@ static inline void nfs_fscache_unregister(void) {}
 static inline void nfs_fscache_get_client_cookie(struct nfs_client *clp) {}
 static inline void nfs_fscache_release_client_cookie(struct nfs_client *clp) {}
 
+static inline void nfs_fscache_get_super_cookie(
+        struct super_block *sb,
+        struct nfs_parsed_mount_data *data)
+{
+}
+static inline void nfs_fscache_release_super_cookie(struct super_block *sb) {}
+
 #endif /* CONFIG_NFS_FSCACHE */
 #endif /* _NFS_FSCACHE_H */