@@ -111,6 +111,7 @@ static int cachefiles_daemon_open(struct inode *inode, struct file *file)
INIT_LIST_HEAD(&cache->volumes);
INIT_LIST_HEAD(&cache->object_list);
spin_lock_init(&cache->object_list_lock);
+ kref_init(&cache->unbind_pincount);
#ifdef CONFIG_CACHEFILES_ONDEMAND
xa_init_flags(&cache->reqs, XA_FLAGS_ALLOC);
xa_init_flags(&cache->ondemand_ids, XA_FLAGS_ALLOC1);
@@ -157,6 +158,25 @@ static void cachefiles_flush_reqs(struct cachefiles_cache *cache)
}
#endif
+static void cachefiles_release_cache(struct kref *kref)
+{
+ struct cachefiles_cache *cache;
+
+ cache = container_of(kref, struct cachefiles_cache, unbind_pincount);
+ cachefiles_daemon_unbind(cache);
+ kfree(cache);
+}
+
+void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache)
+{
+ kref_put(&cache->unbind_pincount, cachefiles_release_cache);
+}
+
+void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache)
+{
+ kref_get(&cache->unbind_pincount);
+}
+
/*
* Release a cache.
*/
@@ -173,14 +193,12 @@ static int cachefiles_daemon_release(struct inode *inode, struct file *file)
#ifdef CONFIG_CACHEFILES_ONDEMAND
cachefiles_flush_reqs(cache);
#endif
- cachefiles_daemon_unbind(cache);
-
/* clean up the control file interface */
cache->cachefilesd = NULL;
file->private_data = NULL;
cachefiles_open = 0;
- kfree(cache);
+ cachefiles_put_unbind_pincount(cache);
_leave("");
return 0;
@@ -109,6 +109,7 @@ struct cachefiles_cache {
char *rootdirname; /* name of cache root directory */
char *secctx; /* LSM security context */
char *tag; /* cache binding tag */
+ struct kref unbind_pincount;/* refcount to do daemon unbind */
#ifdef CONFIG_CACHEFILES_ONDEMAND
struct xarray reqs; /* xarray of pending on-demand requests */
struct xarray ondemand_ids; /* xarray for ondemand_id allocation */
@@ -167,6 +168,8 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache,
* daemon.c
*/
extern const struct file_operations cachefiles_daemon_fops;
+extern void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache);
+extern void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache);
/*
* error_inject.c
@@ -14,6 +14,7 @@ static int cachefiles_ondemand_fd_release(struct inode *inode,
object->ondemand_id = CACHEFILES_ONDEMAND_ID_CLOSED;
xa_erase(&cache->ondemand_ids, object_id);
cachefiles_put_object(object, cachefiles_obj_put_ondemand_fd);
+ cachefiles_put_unbind_pincount(cache);
return 0;
}
@@ -169,6 +170,8 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
load->fd = fd;
req->msg.object_id = object_id;
object->ondemand_id = object_id;
+
+ cachefiles_get_unbind_pincount(cache);
return 0;
err_put_fd:
Add a refcount to avoid the deadlock in on-demand read mode. The on-demand read mode will pin the corresponding cachefiles object for each anonymous fd. The cachefiles object is unpinned when the anonymous fd gets closed. When the user daemon exits and the fd of "/dev/cachefiles" device node gets closed, it will wait for all cahcefiles objects gets withdrawn. Then if there's any anonymous fd getting closed after the fd of the device node, the user daemon will hang forever, waiting for all objects getting withdrawn. To fix this, add a refcount indicating if there's any object pinned by anonymous fds. The cachefiles cache gets unbound and withdrawn when the refcount decreased to 0. It won't change the behaviour of the original mode, in which case the cachefiles cache gets unbound and withdrawn as long as the fd of the device node gets closed. Besides, kref_get() is adequate whilst kref_get_unless_zero() is not needed here, since no more anonymous fd will be created when the .release() callback of the device node fd has already been called. Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> --- fs/cachefiles/daemon.c | 24 +++++++++++++++++++++--- fs/cachefiles/internal.h | 3 +++ fs/cachefiles/ondemand.c | 3 +++ 3 files changed, 27 insertions(+), 3 deletions(-)