[PATCH v5 05/22] cachefiles: notify user daemon when withdrawing cookie

[Jeffle Xu]

Notify user daemon that cookie is going to be withdrawed, providing a
hint that the associated anon_fd can be closed. The anon_fd attached in
the CLOSE request shall be same with that in the previous OPEN request.

Be noted that this is only a hint. User daemon can close the anon_fd
when receiving the CLOSE request, then it will receive another anon_fd
if the cookie gets looked up. Or it can also ignore the CLOSE request,
and keep writing data into the anon_fd. However the next time cookie
gets looked up, the user daemon will still receive another anon_fd.

Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
 fs/cachefiles/daemon.c          | 27 +++++++++++++++++++++++++++
 fs/cachefiles/interface.c       |  2 ++
 fs/cachefiles/internal.h        |  4 ++++
 include/uapi/linux/cachefiles.h |  5 +++++
 4 files changed, 38 insertions(+)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index 3c3a461f8cd8..2ecfdf194206 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -338,6 +338,12 @@ static ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
 		goto err_put_fd;
 	}
 
+	/* CLOSE request doesn't look forward a reply */
+	if (msg->opcode == CACHEFILES_OP_CLOSE) {
+		xa_erase(&cache->reqs, id);
+		complete(&req->done);
+	}
+
 	return n;
 
 err_put_fd:
@@ -452,6 +458,19 @@ static int init_open_req(struct cachefiles_req *req, void *private)
 	return 0;
 }
 
+static int init_close_req(struct cachefiles_req *req, void *private)
+{
+	struct cachefiles_object *object = req->object;
+	struct cachefiles_close *load = (void *)req->msg.data;
+	int fd = object->fd;
+
+	if (WARN_ON_ONCE(fd == -1))
+		return -EIO;
+
+	load->fd = fd;
+	return 0;
+}
+
 int cachefiles_ondemand_init_object(struct cachefiles_object *object)
 {
 	struct fscache_cookie *cookie = object->cookie;
@@ -477,6 +496,14 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
 					    init_open_req, NULL);
 }
 
+void cachefiles_ondemand_cleanup_object(struct cachefiles_object *object)
+{
+	cachefiles_ondemand_send_req(object,
+				     CACHEFILES_OP_CLOSE,
+				     sizeof(struct cachefiles_close),
+				     init_close_req, NULL);
+}
+
 #else
 static inline void cachefiles_ondemand_open(struct cachefiles_cache *cache) {}
 static inline void cachefiles_ondemand_release(struct cachefiles_cache *cache) {}
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index ae93cee9d25d..c5b8fefd4ccc 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -322,6 +322,8 @@ static void cachefiles_commit_object(struct cachefiles_object *object,
 static void cachefiles_clean_up_object(struct cachefiles_object *object,
 				       struct cachefiles_cache *cache)
 {
+	cachefiles_ondemand_cleanup_object(object);
+
 	if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
 		if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 			cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 8450ebd77949..eaac9fae74eb 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -167,6 +167,7 @@ extern const struct file_operations cachefiles_daemon_fops;
 
 #ifdef CONFIG_CACHEFILES_ONDEMAND
 extern int cachefiles_ondemand_init_object(struct cachefiles_object *object);
+extern void cachefiles_ondemand_cleanup_object(struct cachefiles_object *object);
 
 #else
 static inline
@@ -174,6 +175,9 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
 {
 	return 0;
 }
+
+static inline
+void cachefiles_ondemand_cleanup_object(struct cachefiles_object *object) {}
 #endif
 
 /*
diff --git a/include/uapi/linux/cachefiles.h b/include/uapi/linux/cachefiles.h
index 5ea7285863f1..47e53043cfad 100644
--- a/include/uapi/linux/cachefiles.h
+++ b/include/uapi/linux/cachefiles.h
@@ -8,6 +8,7 @@
 
 enum cachefiles_opcode {
 	CACHEFILES_OP_OPEN,
+	CACHEFILES_OP_CLOSE,
 };
 
 /*
@@ -36,4 +37,8 @@ enum cachefiles_open_flags {
 	CACHEFILES_OPEN_WANT_CACHE_SIZE,
 };
 
+struct cachefiles_close {
+	__u32 fd;
+};
+
 #endif
-- 
2.27.0