netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/usb/dwc2/debug.h b/drivers/usb/dwc2/debug.h
new file mode 100644
index 000000000..47252c56d
--- /dev/null
+++ b/drivers/usb/dwc2/debug.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * debug.h - Designware USB2 DRD controller debug header
+ *
+ * Copyright (C) 2015 Intel Corporation
+ * Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
+ */
+
+#include "core.h"
+
+#ifdef CONFIG_DEBUG_FS
+int dwc2_debugfs_init(struct dwc2_hsotg *hsotg);
+void dwc2_debugfs_exit(struct dwc2_hsotg *hsotg);
+#else
+static inline int dwc2_debugfs_init(struct dwc2_hsotg *hsotg)
+{  return 0;  }
+static inline void dwc2_debugfs_exit(struct dwc2_hsotg *hsotg)
+{  }
+#endif