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, 27 insertions, 0 deletions

diff --git a/include/net/firewire.h b/include/net/firewire.h
new file mode 100644
index 000000000..8fbff8d77
--- /dev/null
+++ b/include/net/firewire.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_FIREWIRE_H
+#define _NET_FIREWIRE_H
+
+#include <linux/types.h>
+
+/* Pseudo L2 address */
+#define FWNET_ALEN	16
+union fwnet_hwaddr {
+	u8 u[FWNET_ALEN];
+	/* "Hardware address" defined in RFC2734/RF3146 */
+	struct {
+		__be64 uniq_id;		/* EUI-64			*/
+		u8 max_rec;		/* max packet size		*/
+		u8 sspd;		/* max speed			*/
+		u8 fifo[6];		/* FIFO addr			*/
+	} __packed uc;
+};
+
+/* Pseudo L2 Header */
+#define FWNET_HLEN	18
+struct fwnet_header {
+	u8 h_dest[FWNET_ALEN];	/* destination address */
+	__be16 h_proto;		/* packet type ID field */
+} __packed;
+
+#endif