CIFS: Reopen file before get SMB2 MTU credits for async IO

Currently we get MTU credits before we check an open file if
it needs to be reopened. Reopening the file in such conditions
leads to a possibility of being stuck waiting indefinitely
for credits in the transport layer. Fix this by reopening the
file first if needed and then getting MTU credits for async IO.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/file.c

@@ -2650,6 +2650,14 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 		struct cifs_credits credits_on_stack;
 		struct cifs_credits *credits = &credits_on_stack;
 
+		if (open_file->invalidHandle) {
+			rc = cifs_reopen_file(open_file, false);
+			if (rc == -EAGAIN)
+				continue;
+			else if (rc)
+				break;
+		}
+
 		rc = server->ops->wait_mtu_credits(server, cifs_sb->wsize,
 						   &wsize, credits);
 		if (rc)
@@ -2751,9 +2759,8 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 
 		if (!rc) {
 			if (wdata->cfile->invalidHandle)
-				rc = cifs_reopen_file(wdata->cfile, false);
-
-			if (!rc)
+				rc = -EAGAIN;
+			else
 				rc = server->ops->async_writev(wdata,
 					cifs_uncached_writedata_release);
 		}
@@ -3355,6 +3362,14 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		iov_iter_advance(&direct_iov, offset - ctx->pos);
 
 	do {
+		if (open_file->invalidHandle) {
+			rc = cifs_reopen_file(open_file, true);
+			if (rc == -EAGAIN)
+				continue;
+			else if (rc)
+				break;
+		}
+
 		rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
 						   &rsize, credits);
 		if (rc)
@@ -3438,9 +3453,8 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 
 		if (!rc) {
 			if (rdata->cfile->invalidHandle)
-				rc = cifs_reopen_file(rdata->cfile, true);
-
-			if (!rc)
+				rc = -EAGAIN;
+			else
 				rc = server->ops->async_readv(rdata);
 		}
 
@@ -4127,6 +4141,14 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		struct cifs_credits credits_on_stack;
 		struct cifs_credits *credits = &credits_on_stack;
 
+		if (open_file->invalidHandle) {
+			rc = cifs_reopen_file(open_file, true);
+			if (rc == -EAGAIN)
+				continue;
+			else if (rc)
+				break;
+		}
+
 		rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
 						   &rsize, credits);
 		if (rc)
@@ -4185,9 +4207,8 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 
 		if (!rc) {
 			if (rdata->cfile->invalidHandle)
-				rc = cifs_reopen_file(rdata->cfile, true);
-
-			if (!rc)
+				rc = -EAGAIN;
+			else
 				rc = server->ops->async_readv(rdata);
 		}