cifs: allow for different handling of received response

In order to incorporate async requests, we need to allow for a more
general way to do things on receive, rather than just waking up a
process.

Turn the task pointer in the mid_q_entry into a callback function and a
generic data pointer. When a response comes in, or the socket is
reconnected, cifsd can call the callback function in order to wake up
the process.

The default is to just wake up the current process which should mean no
change in behavior for existing code.

Also, clean up the locking in cifs_reconnect. There doesn't seem to be
any need to hold both the srv_mutex and GlobalMid_Lock when walking the
list of mids.

Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 606ca8bb7102..4de737575959 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -508,6 +508,18 @@ static inline void cifs_stats_bytes_read(struct cifsTconInfo *tcon,
 
 #endif
 
+struct mid_q_entry;
+
+/*
+ * This is the prototype for the mid callback function. When creating one,
+ * take special care to avoid deadlocks. Things to bear in mind:
+ *
+ * - it will be called by cifsd
+ * - the GlobalMid_Lock will be held
+ * - the mid will be removed from the pending_mid_q list
+ */
+typedef void (mid_callback_t)(struct mid_q_entry *mid);
+
 /* one of these for every pending CIFS request to the server */
 struct mid_q_entry {
         struct list_head qhead; /* mids waiting on reply from this server */
@@ -519,7 +531,8 @@ struct mid_q_entry {
         unsigned long when_sent; /* time when smb send finished */
         unsigned long when_received; /* when demux complete (taken off wire) */
 #endif
-        struct task_struct *tsk;        /* task waiting for response */
+        mid_callback_t *callback; /* call completion callback */
+        void *callback_data;      /* general purpose pointer for callback */
         struct smb_hdr *resp_buf;       /* response buffer */
         int midState;   /* wish this were enum but can not pass to wait_event */
         __u8 command;   /* smb command code */