cachefiles: unmark inode in use in error path

Unmark inode in use if error encountered. If the in-use flag leakage
occurs in cachefiles_open_file(), Cachefiles will complain "Inode
already in use" when later another cookie with the same index key is
looked up.

If the in-use flag leakage occurs in cachefiles_create_tmpfile(), though
the "Inode already in use" warning won't be triggered, fix the leakage
anyway.
Reported-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Fixes: 1f08c925 ("cachefiles: Implement backing file wrangling")
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://listman.redhat.com/archives/linux-cachefs/2022-March/006615.html # v1
Link: https://listman.redhat.com/archives/linux-cachefs/2022-March/006618.html # v2

fs/cachefiles/namei.c

@@ -57,6 +57,16 @@ static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
 	trace_cachefiles_mark_inactive(object, inode);
 }
 
+static void cachefiles_do_unmark_inode_in_use(struct cachefiles_object *object,
+					      struct dentry *dentry)
+{
+	struct inode *inode = d_backing_inode(dentry);
+
+	inode_lock(inode);
+	__cachefiles_unmark_inode_in_use(object, dentry);
+	inode_unlock(inode);
+}
+
 /*
  * Unmark a backing inode and tell cachefilesd that there's something that can
  * be culled.
@@ -68,9 +78,7 @@ void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
 	struct inode *inode = file_inode(file);
 
 	if (inode) {
-		inode_lock(inode);
-		__cachefiles_unmark_inode_in_use(object, file->f_path.dentry);
-		inode_unlock(inode);
+		cachefiles_do_unmark_inode_in_use(object, file->f_path.dentry);
 
 		if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 			atomic_long_add(inode->i_blocks, &cache->b_released);
@@ -484,7 +492,7 @@ struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 				object, d_backing_inode(path.dentry), ret,
 				cachefiles_trace_trunc_error);
 			file = ERR_PTR(ret);
-			goto out_dput;
+			goto out_unuse;
 		}
 	}
 
@@ -494,15 +502,20 @@ struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 		trace_cachefiles_vfs_error(object, d_backing_inode(path.dentry),
 					   PTR_ERR(file),
 					   cachefiles_trace_open_error);
-		goto out_dput;
+		goto out_unuse;
 	}
 	if (unlikely(!file->f_op->read_iter) ||
 	    unlikely(!file->f_op->write_iter)) {
 		fput(file);
 		pr_notice("Cache does not support read_iter and write_iter\n");
 		file = ERR_PTR(-EINVAL);
+		goto out_unuse;
 	}
 
+	goto out_dput;
+
+out_unuse:
+	cachefiles_do_unmark_inode_in_use(object, path.dentry);
 out_dput:
 	dput(path.dentry);
 out:
@@ -590,14 +603,16 @@ static bool cachefiles_open_file(struct cachefiles_object *object,
 check_failed:
 	fscache_cookie_lookup_negative(object->cookie);
 	cachefiles_unmark_inode_in_use(object, file);
-	if (ret == -ESTALE) {
-		fput(file);
-		dput(dentry);
+	fput(file);
+	dput(dentry);
+	if (ret == -ESTALE)
 		return cachefiles_create_file(object);
-	}
+	return false;
+
 error_fput:
 	fput(file);
 error:
+	cachefiles_do_unmark_inode_in_use(object, dentry);
 	dput(dentry);
 	return false;
 }