[fuse] fix deadlock between fuse_put_super() and request_end()
A deadlock was possible, when the last reference to the superblock was
held due to a background request containing a file reference.
Releasing the file would release the vfsmount which in turn would
release the superblock. Since sbput_sem is held during the fput() and
fuse_put_super() tries to acquire this same semaphore, a deadlock
results.
The chosen soltuion is to get rid of sbput_sem, and instead use the
spinlock to ensure the referenced inodes/file are released only once.
Since the actual release may sleep, defer these outside the locked
region, but using local variables instead of the structure members.
This is a much more rubust solution.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 19c7185..ee9b830 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -255,15 +255,9 @@
/** waitq for blocked connection */
wait_queue_head_t blocked_waitq;
- /** RW semaphore for exclusion with fuse_put_super() */
- struct rw_semaphore sbput_sem;
-
/** The next unique request id */
u64 reqctr;
- /** Mount is active */
- unsigned mounted;
-
/** Connection established, cleared on umount, connection
abort and device release */
unsigned connected;
@@ -474,11 +468,11 @@
void request_send_background(struct fuse_conn *fc, struct fuse_req *req);
/**
- * Release inodes and file associated with background request
+ * Remove request from the the background list
*/
-void fuse_release_background(struct fuse_conn *fc, struct fuse_req *req);
+void fuse_remove_background(struct fuse_conn *fc, struct fuse_req *req);
-/* Abort all requests */
+/** Abort all requests */
void fuse_abort_conn(struct fuse_conn *fc);
/**