fuse: invalidation reverse calls

Add notification messages that allow the filesystem to invalidate VFS
caches.

Two notifications are added:

 1) inode invalidation

   - invalidate cached attributes
   - invalidate a range of pages in the page cache (this is optional)

 2) dentry invalidation

   - try to invalidate a subtree in the dentry cache

Care must be taken while accessing the 'struct super_block' for the
mount, as it can go away while an invalidation is in progress.  To
prevent this, introduce a rw-semaphore, that is taken for read during
the invalidation and taken for write in the ->kill_sb callback.

Cc: Csaba Henk <csaba@gluster.com>
Cc: Anand Avati <avati@zresearch.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index ede4f77b2d6c..52b641fc0faf 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -484,6 +484,12 @@ struct fuse_conn {
 
         /** Called on final put */
         void (*release)(struct fuse_conn *);
+
+        /** Super block for this connection. */
+        struct super_block *sb;
+
+        /** Read/write semaphore to hold when accessing sb. */
+        struct rw_semaphore killsb;
 };
 
 static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
@@ -512,6 +518,11 @@ extern const struct file_operations fuse_dev_operations;
 extern const struct dentry_operations fuse_dentry_operations;
 
 /**
+ * Inode to nodeid comparison.
+ */
+int fuse_inode_eq(struct inode *inode, void *_nodeidp);
+
+/**
  * Get a filled in inode
  */
 struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
@@ -711,6 +722,19 @@ void fuse_release_nowrite(struct inode *inode);
 
 u64 fuse_get_attr_version(struct fuse_conn *fc);
 
+/**
+ * File-system tells the kernel to invalidate cache for the given node id.
+ */
+int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
+                             loff_t offset, loff_t len);
+
+/**
+ * File-system tells the kernel to invalidate parent attributes and
+ * the dentry matching parent/name.
+ */
+int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
+                             struct qstr *name);
+
 int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
                  bool isdir);
 ssize_t fuse_direct_io(struct file *file, const char __user *buf,