smb3: Call cifs reconnect from demultiplex thread

cifs_reconnect needs to be called only from demultiplex thread.
skip cifs_reconnect in offload thread. So, cifs_reconnect will be
called by demultiplex thread in subsequent request.

These patches address a problem found during decryption offload:
     CIFS: VFS: trying to dequeue a deleted mid
that can cause a refcount use after free:

[ 1271.389453] Workqueue: smb3decryptd smb2_decrypt_offload [cifs]
[ 1271.389456] RIP: 0010:refcount_warn_saturate+0xae/0xf0
[ 1271.389457] Code: fa 1d 6a 01 01 e8 c7 44 b1 ff 0f 0b 5d c3 80 3d e7 1d 6a 01 00 75 91 48 c7 c7 d8 be 1d a2 c6 05 d7 1d 6a 01 01 e8 a7 44 b1 ff <0f> 0b 5d c3 80 3d c5 1d 6a 01 00 0f 85 6d ff ff ff 48 c7 c7 30 bf
[ 1271.389458] RSP: 0018:ffffa4cdc1f87e30 EFLAGS: 00010286
[ 1271.389458] RAX: 0000000000000000 RBX: ffff9974d2809f00 RCX: ffff9974df898cc8
[ 1271.389459] RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff9974df898cc0
[ 1271.389460] RBP: ffffa4cdc1f87e30 R08: 0000000000000004 R09: 00000000000002c0
[ 1271.389460] R10: 0000000000000000 R11: 0000000000000001 R12: ffff9974b7fdb5c0
[ 1271.389461] R13: ffff9974d2809f00 R14: ffff9974ccea0a80 R15: ffff99748e60db80
[ 1271.389462] FS:  0000000000000000(0000) GS:ffff9974df880000(0000) knlGS:0000000000000000
[ 1271.389462] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1271.389463] CR2: 000055c60f344fe4 CR3: 0000001031a3c002 CR4: 00000000003706e0
[ 1271.389465] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1271.389465] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1271.389466] Call Trace:
[ 1271.389483]  cifs_mid_q_entry_release+0xce/0x110 [cifs]
[ 1271.389499]  smb2_decrypt_offload+0xa9/0x1c0 [cifs]
[ 1271.389501]  process_one_work+0x1e8/0x3b0
[ 1271.389503]  worker_thread+0x50/0x370
[ 1271.389504]  kthread+0x12f/0x150
[ 1271.389506]  ? process_one_work+0x3b0/0x3b0
[ 1271.389507]  ? __kthread_bind_mask+0x70/0x70
[ 1271.389509]  ret_from_fork+0x22/0x30

Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org> #5.4+
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: rohiths-msft

fs/cifs/smb2ops.c

@@ -4356,7 +4356,8 @@ init_read_bvec(struct page **pages, unsigned int npages, unsigned int data_size,
 static int
 handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 		 char *buf, unsigned int buf_len, struct page **pages,
-		 unsigned int npages, unsigned int page_data_size)
+		 unsigned int npages, unsigned int page_data_size,
+		 bool is_offloaded)
 {
 	unsigned int data_offset;
 	unsigned int data_len;
@@ -4378,7 +4379,8 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 
 	if (server->ops->is_session_expired &&
 	    server->ops->is_session_expired(buf)) {
-		cifs_reconnect(server);
+		if (!is_offloaded)
+			cifs_reconnect(server);
 		return -1;
 	}
 
@@ -4518,7 +4520,8 @@ static void smb2_decrypt_offload(struct work_struct *work)
 		mid->decrypted = true;
 		rc = handle_read_data(dw->server, mid, dw->buf,
 				      dw->server->vals->read_rsp_size,
-				      dw->ppages, dw->npages, dw->len);
+				      dw->ppages, dw->npages, dw->len,
+				      true);
 		mid->callback(mid);
 		cifs_mid_q_entry_release(mid);
 	}
@@ -4622,7 +4625,7 @@ receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid,
 		(*mid)->decrypted = true;
 		rc = handle_read_data(server, *mid, buf,
 				      server->vals->read_rsp_size,
-				      pages, npages, len);
+				      pages, npages, len, false);
 	}
 
 free_pages:
@@ -4765,7 +4768,7 @@ smb3_handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	char *buf = server->large_buf ? server->bigbuf : server->smallbuf;
 
 	return handle_read_data(server, mid, buf, server->pdu_size,
-				NULL, 0, 0);
+				NULL, 0, 0, false);
 }
 
 static int