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, 176 insertions, 0 deletions

diff --git a/fs/9p/cache.h b/fs/9p/cache.h
new file mode 100644
index 0000000..a94192b
--- /dev/null
+++ b/fs/9p/cache.h
@@ -0,0 +1,176 @@
+/*
+ * V9FS cache definitions.
+ *
+ *  Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to:
+ *  Free Software Foundation
+ *  51 Franklin Street, Fifth Floor
+ *  Boston, MA  02111-1301  USA
+ *
+ */
+
+#ifndef _9P_CACHE_H
+#ifdef CONFIG_9P_FSCACHE
+#include <linux/fscache.h>
+#include <linux/spinlock.h>
+
+extern struct kmem_cache *vcookie_cache;
+
+struct v9fs_cookie {
+	spinlock_t lock;
+	struct inode inode;
+	struct fscache_cookie *fscache;
+	struct p9_qid *qid;
+};
+
+static inline struct v9fs_cookie *v9fs_inode2cookie(const struct inode *inode)
+{
+	return container_of(inode, struct v9fs_cookie, inode);
+}
+
+extern struct fscache_netfs v9fs_cache_netfs;
+extern const struct fscache_cookie_def v9fs_cache_session_index_def;
+extern const struct fscache_cookie_def v9fs_cache_inode_index_def;
+
+extern void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses);
+extern void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses);
+
+extern void v9fs_cache_inode_get_cookie(struct inode *inode);
+extern void v9fs_cache_inode_put_cookie(struct inode *inode);
+extern void v9fs_cache_inode_flush_cookie(struct inode *inode);
+extern void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp);
+extern void v9fs_cache_inode_reset_cookie(struct inode *inode);
+
+extern int __v9fs_cache_register(void);
+extern void __v9fs_cache_unregister(void);
+
+extern int __v9fs_fscache_release_page(struct page *page, gfp_t gfp);
+extern void __v9fs_fscache_invalidate_page(struct page *page);
+extern int __v9fs_readpage_from_fscache(struct inode *inode,
+					struct page *page);
+extern int __v9fs_readpages_from_fscache(struct inode *inode,
+					 struct address_space *mapping,
+					 struct list_head *pages,
+					 unsigned *nr_pages);
+extern void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page);
+
+
+/**
+ * v9fs_cache_register - Register v9fs file system with the cache
+ */
+static inline int v9fs_cache_register(void)
+{
+	return __v9fs_cache_register();
+}
+
+/**
+ * v9fs_cache_unregister - Unregister v9fs from the cache
+ */
+static inline void v9fs_cache_unregister(void)
+{
+	__v9fs_cache_unregister();
+}
+
+static inline int v9fs_fscache_release_page(struct page *page,
+					    gfp_t gfp)
+{
+	return __v9fs_fscache_release_page(page, gfp);
+}
+
+static inline void v9fs_fscache_invalidate_page(struct page *page)
+{
+	__v9fs_fscache_invalidate_page(page);
+}
+
+static inline int v9fs_readpage_from_fscache(struct inode *inode,
+					     struct page *page)
+{
+	return __v9fs_readpage_from_fscache(inode, page);
+}
+
+static inline int v9fs_readpages_from_fscache(struct inode *inode,
+					      struct address_space *mapping,
+					      struct list_head *pages,
+					      unsigned *nr_pages)
+{
+	return __v9fs_readpages_from_fscache(inode, mapping, pages,
+					     nr_pages);
+}
+
+static inline void v9fs_readpage_to_fscache(struct inode *inode,
+					    struct page *page)
+{
+	if (PageFsCache(page))
+		__v9fs_readpage_to_fscache(inode, page);
+}
+
+static inline void v9fs_uncache_page(struct inode *inode, struct page *page)
+{
+	struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
+	fscache_uncache_page(vcookie->fscache, page);
+	BUG_ON(PageFsCache(page));
+}
+
+static inline void v9fs_vcookie_set_qid(struct inode *inode,
+					struct p9_qid *qid)
+{
+	struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
+	spin_lock(&vcookie->lock);
+	vcookie->qid = qid;
+	spin_unlock(&vcookie->lock);
+}
+
+#else /* CONFIG_9P_FSCACHE */
+
+static inline int v9fs_cache_register(void)
+{
+	return 1;
+}
+
+static inline void v9fs_cache_unregister(void) {}
+
+static inline int v9fs_fscache_release_page(struct page *page,
+					    gfp_t gfp) {
+	return 1;
+}
+
+static inline void v9fs_fscache_invalidate_page(struct page *page) {}
+
+static inline int v9fs_readpage_from_fscache(struct inode *inode,
+					     struct page *page)
+{
+	return -ENOBUFS;
+}
+
+static inline int v9fs_readpages_from_fscache(struct inode *inode,
+					      struct address_space *mapping,
+					      struct list_head *pages,
+					      unsigned *nr_pages)
+{
+	return -ENOBUFS;
+}
+
+static inline void v9fs_readpage_to_fscache(struct inode *inode,
+					    struct page *page)
+{}
+
+static inline void v9fs_uncache_page(struct inode *inode, struct page *page)
+{}
+
+static inline void v9fs_vcookie_set_qid(struct inode *inode,
+					struct p9_qid *qid)
+{}
+
+#endif /* CONFIG_9P_FSCACHE */
+#endif /* _9P_CACHE_H */