fs/9p: Move writeback fid to v9fs_inode

index ce59d15..f7f3f00 100644
@@ -122,6 +122,8 @@ struct v9fs_inode {
 	struct fscache_cookie *fscache;
 	struct p9_qid *fscache_key;
 #endif
+	struct p9_fid *writeback_fid;
+	struct mutex v_mutex;
 	struct inode vfs_inode;
 };
 

index 566684c..ee45552 100644
@@ -163,8 +163,10 @@ static int v9fs_vfs_writepage_locked(struct page *page)
 	int retval, len;
 	loff_t offset, size;
 	mm_segment_t old_fs;
+	struct v9fs_inode *v9inode;
 	struct inode *inode = page->mapping->host;
 
+	v9inode = V9FS_I(inode);
 	size = i_size_read(inode);
 	if (page->index == size >> PAGE_CACHE_SHIFT)
 		len = size & ~PAGE_CACHE_MASK;

@@ -178,11 +180,11 @@ static int v9fs_vfs_writepage_locked(struct page *page)
 
 	old_fs = get_fs();
 	set_fs(get_ds());
-	/* We should have i_private always set */
-	BUG_ON(!inode->i_private);
+	/* We should have writeback_fid always set */
+	BUG_ON(!v9inode->writeback_fid);
 
 	retval = v9fs_file_write_internal(inode,
-					  (struct p9_fid *)inode->i_private,
+					  v9inode->writeback_fid,
 					  (__force const char __user *)buffer,
 					  len, &offset, 0);
 	if (retval > 0)

@@ -274,23 +276,25 @@ static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 {
 	int retval = 0;
 	struct page *page;
+	struct v9fs_inode *v9inode;
 	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 	struct inode *inode = mapping->host;
 
+	v9inode = V9FS_I(inode);
 start:
 	page = grab_cache_page_write_begin(mapping, index, flags);
 	if (!page) {
 		retval = -ENOMEM;
 		goto out;
 	}
-	BUG_ON(!inode->i_private);
+	BUG_ON(!v9inode->writeback_fid);
 	if (PageUptodate(page))
 		goto out;
 
 	if (len == PAGE_CACHE_SIZE)
 		goto out;
 
-	retval = v9fs_fid_readpage(inode->i_private, page);
+	retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 	page_cache_release(page);
 	if (!retval)
 		goto start;

index f7b571d..94f6e84 100644
@@ -56,11 +56,13 @@ static const struct vm_operations_struct v9fs_file_vm_ops;
 int v9fs_file_open(struct inode *inode, struct file *file)
 {
 	int err;
+	struct v9fs_inode *v9inode;
 	struct v9fs_session_info *v9ses;
 	struct p9_fid *fid;
 	int omode;
 
 	P9_DPRINTK(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file);
+	v9inode = V9FS_I(inode);
 	v9ses = v9fs_inode2v9ses(inode);
 	if (v9fs_proto_dotl(v9ses))
 		omode = file->f_flags;

@@ -88,9 +90,10 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 	}
 
 	file->private_data = fid;
-	if (v9ses->cache && !inode->i_private) {
+	mutex_lock(&v9inode->v_mutex);
+	if (v9ses->cache && !v9inode->writeback_fid) {
 		/*
-		 * clone a fid and add it to inode->i_private
+		 * clone a fid and add it to writeback_fid
 		 * we do it during open time instead of
 		 * page dirty time via write_begin/page_mkwrite
 		 * because we want write after unlink usecase

@@ -99,10 +102,12 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 		fid = v9fs_writeback_fid(file->f_path.dentry);
 		if (IS_ERR(fid)) {
 			err = PTR_ERR(fid);
+			mutex_unlock(&v9inode->v_mutex);
 			goto out_error;
 		}
-		inode->i_private = (void *) fid;
+		v9inode->writeback_fid = (void *) fid;
 	}
+	mutex_unlock(&v9inode->v_mutex);
 #ifdef CONFIG_9P_FSCACHE
 	if (v9ses->cache)
 		v9fs_cache_inode_set_cookie(inode, file);

@@ -550,6 +555,7 @@ v9fs_file_mmap(struct file *file, struct vm_area_struct *vma)
 static int
 v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
+	struct v9fs_inode *v9inode;
 	struct page *page = vmf->page;
 	struct file *filp = vma->vm_file;
 	struct inode *inode = filp->f_path.dentry->d_inode;

@@ -558,9 +564,10 @@ v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	P9_DPRINTK(P9_DEBUG_VFS, "page %p fid %lx\n",
 		   page, (unsigned long)filp->private_data);
 
+	v9inode = V9FS_I(inode);
 	/* make sure the cache has finished storing the page */
 	v9fs_fscache_wait_on_page_write(inode, page);
-	BUG_ON(!inode->i_private);
+	BUG_ON(!v9inode->writeback_fid);
 	lock_page(page);
 	if (page->mapping != inode->i_mapping)
 		goto out_unlock;

index 0c104ab..87949db 100644
@@ -219,6 +219,8 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 	v9inode->fscache_key = NULL;
 	spin_lock_init(&v9inode->fscache_lock);
 #endif
+	v9inode->writeback_fid = NULL;
+	mutex_init(&v9inode->v_mutex);
 	return &v9inode->vfs_inode;
 }
 

@@ -413,6 +415,8 @@ error:
  */
 void v9fs_evict_inode(struct inode *inode)
 {
+	struct v9fs_inode *v9inode = V9FS_I(inode);
+
 	truncate_inode_pages(inode->i_mapping, 0);
 	end_writeback(inode);
 	filemap_fdatawrite(inode->i_mapping);

@@ -420,10 +424,10 @@ void v9fs_evict_inode(struct inode *inode)
 #ifdef CONFIG_9P_FSCACHE
 	v9fs_cache_inode_put_cookie(inode);
 #endif
-	/* clunk the fid stashed in inode->i_private */
-	if (inode->i_private) {
-		p9_client_clunk((struct p9_fid *)inode->i_private);
-		inode->i_private = NULL;
+	/* clunk the fid stashed in writeback_fid */
+	if (v9inode->writeback_fid) {
+		p9_client_clunk(v9inode->writeback_fid);
+		v9inode->writeback_fid = NULL;
 	}
 }
 

@@ -606,9 +610,10 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 	int err;
 	u32 perm;
 	int flags;
+	struct file *filp;
+	struct v9fs_inode *v9inode;
 	struct v9fs_session_info *v9ses;
 	struct p9_fid *fid, *inode_fid;
-	struct file *filp;
 
 	err = 0;
 	fid = NULL;

@@ -630,9 +635,11 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 
 	/* if we are opening a file, assign the open fid to the file */
 	if (nd && nd->flags & LOOKUP_OPEN) {
-		if (v9ses->cache && !dentry->d_inode->i_private) {
+		v9inode = V9FS_I(dentry->d_inode);
+		mutex_lock(&v9inode->v_mutex);
+		if (v9ses->cache && !v9inode->writeback_fid) {
 			/*
-			 * clone a fid and add it to inode->i_private
+			 * clone a fid and add it to writeback_fid
 			 * we do it during open time instead of
 			 * page dirty time via write_begin/page_mkwrite
 			 * because we want write after unlink usecase

@@ -641,10 +648,12 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 			inode_fid = v9fs_writeback_fid(dentry);
 			if (IS_ERR(inode_fid)) {
 				err = PTR_ERR(inode_fid);
+				mutex_unlock(&v9inode->v_mutex);
 				goto error;
 			}
-			dentry->d_inode->i_private = (void *) inode_fid;
+			v9inode->writeback_fid = (void *) inode_fid;
 		}
+		mutex_unlock(&v9inode->v_mutex);
 		filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
 		if (IS_ERR(filp)) {
 			err = PTR_ERR(filp);

index 21523f2..d144894 100644
@@ -159,16 +159,17 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
 		struct nameidata *nd)
 {
 	int err = 0;
-	char *name = NULL;
 	gid_t gid;
 	int flags;
 	mode_t mode;
-	struct v9fs_session_info *v9ses;
-	struct p9_fid *fid = NULL;
-	struct p9_fid *dfid, *ofid, *inode_fid;
+	char *name = NULL;
 	struct file *filp;
 	struct p9_qid qid;
 	struct inode *inode;
+	struct p9_fid *fid = NULL;
+	struct v9fs_inode *v9inode;
+	struct p9_fid *dfid, *ofid, *inode_fid;
+	struct v9fs_session_info *v9ses;
 	struct posix_acl *pacl = NULL, *dacl = NULL;
 
 	v9ses = v9fs_inode2v9ses(dir);

@@ -241,9 +242,12 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
 
 	/* Now set the ACL based on the default value */
 	v9fs_set_create_acl(dentry, dacl, pacl);
-	if (v9ses->cache && !inode->i_private) {
+
+	v9inode = V9FS_I(inode);
+	mutex_lock(&v9inode->v_mutex);
+	if (v9ses->cache && !v9inode->writeback_fid) {
 		/*
-		 * clone a fid and add it to inode->i_private
+		 * clone a fid and add it to writeback_fid
 		 * we do it during open time instead of
 		 * page dirty time via write_begin/page_mkwrite
 		 * because we want write after unlink usecase

@@ -252,10 +256,12 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
 		inode_fid = v9fs_writeback_fid(dentry);
 		if (IS_ERR(inode_fid)) {
 			err = PTR_ERR(inode_fid);
+			mutex_unlock(&v9inode->v_mutex);
 			goto error;
 		}
-		inode->i_private = (void *) inode_fid;
+		v9inode->writeback_fid = (void *) inode_fid;
 	}
+	mutex_unlock(&v9inode->v_mutex);
 	/* Since we are opening a file, assign the open fid to the file */
 	filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
 	if (IS_ERR(filp)) {