fscache: Attach the index key and aux data to the cookie

Attach copies of the index key and auxiliary data to the fscache cookie so
that:

 (1) The callbacks to the netfs for this stuff can be eliminated.  This
     can simplify things in the cache as the information is still
     available, even after the cache has relinquished the cookie.

 (2) Simplifies the locking requirements of accessing the information as we
     don't have to worry about the netfs object going away on us.

 (3) The cache can do lazy updating of the coherency information on disk.
     As long as the cache is flushed before reboot/poweroff, there's no
     need to update the coherency info on disk every time it changes.

 (4) Cookies can be hashed or put in a tree as the index key is easily
     available.  This allows:

     (a) Checks for duplicate cookies can be made at the top fscache layer
     	 rather than down in the bowels of the cache backend.

     (b) Caching can be added to a netfs object that has a cookie if the
     	 cache is brought online after the netfs object is allocated.

A certain amount of space is made in the cookie for inline copies of the
data, but if it won't fit there, extra memory will be allocated for it.

The downside of this is that live cache operation requires more memory.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Anna Schumaker <anna.schumaker@netapp.com>
Tested-by: Steve Dickson <steved@redhat.com>

1 files changed, 37 insertions, 9 deletions

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index c942c79fc5f0..e499713efd2e 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -243,6 +243,33 @@ struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
 }
 
 /*
+ * Get a cache cookie for an inode.
+ */
+static void afs_get_inode_cache(struct afs_vnode *vnode)
+{
+#ifdef CONFIG_AFS_FSCACHE
+	struct {
+		u32 vnode_id;
+		u32 unique;
+		u32 vnode_id_ext[2];	/* Allow for a 96-bit key */
+	} __packed key;
+	struct afs_vnode_cache_aux aux;
+
+	key.vnode_id		= vnode->fid.vnode;
+	key.unique		= vnode->fid.unique;
+	key.vnode_id_ext[0]	= 0;
+	key.vnode_id_ext[1]	= 0;
+	aux.data_version	= vnode->status.data_version;
+
+	vnode->cache = fscache_acquire_cookie(vnode->volume->cache,
+					      &afs_vnode_cache_index_def,
+					      &key, sizeof(key),
+					      &aux, sizeof(aux),
+					      vnode, true);
+#endif
+}
+
+/*
  * inode retrieval
  */
 struct inode *afs_iget(struct super_block *sb, struct key *key,
@@ -307,11 +334,7 @@ struct inode *afs_iget(struct super_block *sb, struct key *key,
 	/* set up caching before mapping the status, as map-status reads the
 	 * first page of symlinks to see if they're really mountpoints */
 	inode->i_size = vnode->status.size;
-#ifdef CONFIG_AFS_FSCACHE
-	vnode->cache = fscache_acquire_cookie(vnode->volume->cache,
-					      &afs_vnode_cache_index_def,
-					      vnode, true);
-#endif
+	afs_get_inode_cache(vnode);
 
 	ret = afs_inode_map_status(vnode, key);
 	if (ret < 0)
@@ -327,7 +350,7 @@ struct inode *afs_iget(struct super_block *sb, struct key *key,
 	/* failure */
 bad_inode:
 #ifdef CONFIG_AFS_FSCACHE
-	fscache_relinquish_cookie(vnode->cache, ret == -ENOENT);
+	fscache_relinquish_cookie(vnode->cache, NULL, ret == -ENOENT);
 	vnode->cache = NULL;
 #endif
 	iget_failed(inode);
@@ -511,9 +534,14 @@ void afs_evict_inode(struct inode *inode)
 	}
 
 #ifdef CONFIG_AFS_FSCACHE
-	fscache_relinquish_cookie(vnode->cache,
-				  test_bit(AFS_VNODE_DELETED, &vnode->flags));
-	vnode->cache = NULL;
+	{
+		struct afs_vnode_cache_aux aux;
+
+		aux.data_version = vnode->status.data_version;
+		fscache_relinquish_cookie(vnode->cache, &aux,
+					  test_bit(AFS_VNODE_DELETED, &vnode->flags));
+		vnode->cache = NULL;
+	}
 #endif
 
 	afs_put_permits(vnode->permit_cache);