cachefiles: notify the user daemon when withdrawing cookie

Notify the user daemon that cookie is going to be withdrawn, providing a
hint that the associated anonymous fd can be closed.

Be noted that this is only a hint. The user daemon may close the
associated anonymous fd when receiving the CLOSE request, then it will
receive another anonymous fd when the cookie gets looked up. Or it may
ignore the CLOSE request, and keep writing data through the anonymous
fd. However the next time the cookie gets looked up, the user daemon
will still receive another new anonymous fd.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Acked-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20220425122143.56815-5-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index ae93cee9d25ded5f64c23e9a8f8e0e63864fc494..a69073a1d3f0693b3b90fdc56af1bd85fc4eb14e 100644 (file)
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -362,6 +362,8 @@ static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
                spin_unlock(&cache->object_list_lock);
        }
 
+       cachefiles_ondemand_clean_object(object);
+
        if (object->file) {
                cachefiles_begin_secure(cache, &saved_cred);
                cachefiles_clean_up_object(object, cache);

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index e5c612888f84637ffab372f835465b6e7b71d756..da388ba127ebbe6102084764b3c5c65306852cc8 100644 (file)
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -290,6 +290,7 @@ extern int cachefiles_ondemand_copen(struct cachefiles_cache *cache,
                                     char *args);
 
 extern int cachefiles_ondemand_init_object(struct cachefiles_object *object);
+extern void cachefiles_ondemand_clean_object(struct cachefiles_object *object);
 
 #else
 static inline ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
@@ -302,6 +303,10 @@ static inline int cachefiles_ondemand_init_object(struct cachefiles_object *obje
 {
        return 0;
 }
+
+static inline void cachefiles_ondemand_clean_object(struct cachefiles_object *object)
+{
+}
 #endif
 
 /*

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 7946ee6c40bef00a6b67ce1ee2a109804ec3b1f8..11b1c15ac69797b3283e4029c7eb9e4e6c034adc 100644 (file)
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -229,6 +229,12 @@ 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:
@@ -300,6 +306,13 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
                /* coupled with the barrier in cachefiles_flush_reqs() */
                smp_mb();
 
+               if (opcode != CACHEFILES_OP_OPEN && object->ondemand_id <= 0) {
+                       WARN_ON_ONCE(object->ondemand_id == 0);
+                       xas_unlock(&xas);
+                       ret = -EIO;
+                       goto out;
+               }
+
                xas.xa_index = 0;
                xas_find_marked(&xas, UINT_MAX, XA_FREE_MARK);
                if (xas.xa_node == XAS_RESTART)
@@ -356,6 +369,25 @@ static int cachefiles_ondemand_init_open_req(struct cachefiles_req *req,
        return 0;
 }
 
+static int cachefiles_ondemand_init_close_req(struct cachefiles_req *req,
+                                             void *private)
+{
+       struct cachefiles_object *object = req->object;
+       int object_id = object->ondemand_id;
+
+       /*
+        * It's possible that object id is still 0 if the cookie looking up
+        * phase failed before OPEN request has ever been sent. Also avoid
+        * sending CLOSE request for CACHEFILES_ONDEMAND_ID_CLOSED, which means
+        * anon_fd has already been closed.
+        */
+       if (object_id <= 0)
+               return -ENOENT;
+
+       req->msg.object_id = object_id;
+       return 0;
+}
+
 int cachefiles_ondemand_init_object(struct cachefiles_object *object)
 {
        struct fscache_cookie *cookie = object->cookie;
@@ -379,3 +411,9 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
        return cachefiles_ondemand_send_req(object, CACHEFILES_OP_OPEN,
                        data_len, cachefiles_ondemand_init_open_req, NULL);
 }
+
+void cachefiles_ondemand_clean_object(struct cachefiles_object *object)
+{
+       cachefiles_ondemand_send_req(object, CACHEFILES_OP_CLOSE, 0,
+                       cachefiles_ondemand_init_close_req, NULL);
+}

diff --git a/include/uapi/linux/cachefiles.h b/include/uapi/linux/cachefiles.h
index 521f2fe4fe9c1a9e70571f8fb66922f383d26222..37a0071037c8cdf60bf5e9eeefcd9582275ea852 100644 (file)
--- 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,
 };
 
 /*