9p: Add fscache support to 9p

This patch adds a persistent, read-only caching facility for
9p clients using the FS-Cache caching backend.

When the fscache facility is enabled, each inode is associated
with a corresponding vcookie which is an index into the FS-Cache
indexing tree. The FS-Cache indexing tree is indexed at 3 levels:
- session object associated with each mount.
- inode/vcookie
- actual data (pages)

A cache tag is chosen randomly for each session. These tags can
be read off /sys/fs/9p/caches and can be passed as a mount-time
parameter to re-attach to the specified caching session.

Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 56 insertions, 1 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index f3bfa87926bd..5947628aefef 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -40,6 +40,7 @@
 #include "v9fs.h"
 #include "v9fs_vfs.h"
 #include "fid.h"
+#include "cache.h"
 
 static const struct inode_operations v9fs_dir_inode_operations;
 static const struct inode_operations v9fs_dir_inode_operations_ext;
@@ -197,6 +198,39 @@ v9fs_blank_wstat(struct p9_wstat *wstat)
         wstat->extension = NULL;
 }
 
+#ifdef CONFIG_9P_FSCACHE
+/**
+ * v9fs_alloc_inode - helper function to allocate an inode
+ * This callback is executed before setting up the inode so that we
+ * can associate a vcookie with each inode.
+ *
+ */
+
+struct inode *v9fs_alloc_inode(struct super_block *sb)
+{
+        struct v9fs_cookie *vcookie;
+        vcookie = (struct v9fs_cookie *)kmem_cache_alloc(vcookie_cache,
+                                                         GFP_KERNEL);
+        if (!vcookie)
+                return NULL;
+
+        vcookie->fscache = NULL;
+        vcookie->qid = NULL;
+        spin_lock_init(&vcookie->lock);
+        return &vcookie->inode;
+}
+
+/**
+ * v9fs_destroy_inode - destroy an inode
+ *
+ */
+
+void v9fs_destroy_inode(struct inode *inode)
+{
+        kmem_cache_free(vcookie_cache, v9fs_inode2cookie(inode));
+}
+#endif
+
 /**
  * v9fs_get_inode - helper function to setup an inode
  * @sb: superblock
@@ -326,6 +360,21 @@ error:
 }
 */
 
+
+/**
+ * v9fs_clear_inode - release an inode
+ * @inode: inode to release
+ *
+ */
+void v9fs_clear_inode(struct inode *inode)
+{
+        filemap_fdatawrite(inode->i_mapping);
+
+#ifdef CONFIG_9P_FSCACHE
+        v9fs_cache_inode_put_cookie(inode);
+#endif
+}
+
 /**
  * v9fs_inode_from_fid - populate an inode by issuing a attribute request
  * @v9ses: session information
@@ -356,8 +405,14 @@ v9fs_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
 
         v9fs_stat2inode(st, ret, sb);
         ret->i_ino = v9fs_qid2ino(&st->qid);
+
+#ifdef CONFIG_9P_FSCACHE
+        v9fs_vcookie_set_qid(ret, &st->qid);
+        v9fs_cache_inode_get_cookie(ret);
+#endif
         p9stat_free(st);
         kfree(st);
+
         return ret;
 
 error:
@@ -751,7 +806,7 @@ v9fs_vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
         P9_DPRINTK(P9_DEBUG_VFS, "dentry: %p\n", dentry);
         err = -EPERM;
         v9ses = v9fs_inode2v9ses(dentry->d_inode);
-        if (v9ses->cache == CACHE_LOOSE)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 return simple_getattr(mnt, dentry, stat);
 
         fid = v9fs_fid_lookup(dentry);