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, 9 insertions, 0 deletions

diff --git a/fs/9p/Kconfig b/fs/9p/Kconfig
index 74e0723e90bc..795233702a4e 100644
--- a/fs/9p/Kconfig
+++ b/fs/9p/Kconfig
@@ -8,3 +8,12 @@ config 9P_FS
           See <http://v9fs.sf.net> for more information.
 
           If unsure, say N.
+
+config 9P_FSCACHE
+        bool "Enable 9P client caching support (EXPERIMENTAL)"
+        depends on EXPERIMENTAL
+        depends on 9P_FS=m && FSCACHE || 9P_FS=y && FSCACHE=y
+        help
+          Choose Y here to enable persistent, read-only local
+          caching support for 9p clients using FS-Cache
+