[PATCH v6 04/22] cachefiles: notify user daemon when withdrawing cookie

Jeffle Xu
2022-03-25T12:22:44Z

Notify user daemon that cookie is going to be withdrawn, providing a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@linux.alibaba.com>
---
fs/cachefiles/interface.c | 2 ++
fs/cachefiles/internal.h | 3 +++
fs/cachefiles/ondemand.c | 27 +++++++++++++++++++++++++++
include/uapi/linux/cachefiles.h | 5 +++++
4 files changed, 37 insertions(+)

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 8a0f1b691aca..c80b519a887b 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -280,6 +280,7 @@ extern int cachefiles_ondemand_cinit(struct cachefiles_cache *cache,
char *args);

extern int cachefiles_ondemand_init_object(struct cachefiles_object *object);
+extern void cachefiles_ondemand_cleanup_object(struct cachefiles_object *object);

#else
ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
@@ -292,6 +293,8 @@ static inline int cachefiles_ondemand_init_object(struct cachefiles_object *obje
{
return 0;
}
+
+static inline void cachefiles_ondemand_cleanup_object(struct cachefiles_object *object) {}
#endif

/*
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 0742c4a7797a..7fd518e01e5a 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -199,6 +199,12 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
goto err_put_fd;
}

+ /* CLOSE request has no reply */
+ if (msg->opcode == CACHEFILES_OP_CLOSE) {
+ xa_erase(&cache->reqs, id);
+ complete(&req->done);
+ }
+
return n;

err_put_fd:
@@ -322,6 +328,19 @@ 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;
@@ -346,3 +365,11 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
CACHEFILES_OP_OPEN, data_len,
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);
+}
diff --git a/include/uapi/linux/cachefiles.h b/include/uapi/linux/cachefiles.h
index 0c44d68be6bd..03047e4b7df2 100644
--- a/include/uapi/linux/cachefiles.h
+++ b/include/uapi/linux/cachefiles.h
@@ -12,6 +12,7 @@

enum cachefiles_opcode {
CACHEFILES_OP_OPEN,
+ CACHEFILES_OP_CLOSE,
};

/*
@@ -40,4 +41,8 @@ enum cachefiles_open_flags {
CACHEFILES_OPEN_WANT_CACHE_SIZE,
};

+struct cachefiles_close {
+ __u32 fd;
+};
+
#endif
--
2.27.0