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, 119 insertions, 0 deletions

diff --git a/include/net/protocol.h b/include/net/protocol.h
new file mode 100644
index 000000000..b2499f88f
--- /dev/null
+++ b/include/net/protocol.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Definitions for the protocol dispatcher.
+ *
+ * Version:	@(#)protocol.h	1.0.2	05/07/93
+ *
+ * Author:	Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *
+ *	Changes:
+ *		Alan Cox	:	Added a name field and a frag handler
+ *					field for later.
+ *		Alan Cox	:	Cleaned up, and sorted types.
+ *		Pedro Roque	:	inet6 protocols
+ */
+ 
+#ifndef _PROTOCOL_H
+#define _PROTOCOL_H
+
+#include <linux/in6.h>
+#include <linux/skbuff.h>
+#if IS_ENABLED(CONFIG_IPV6)
+#include <linux/ipv6.h>
+#endif
+#include <linux/netdevice.h>
+
+/* This is one larger than the largest protocol value that can be
+ * found in an ipv4 or ipv6 header.  Since in both cases the protocol
+ * value is presented in a __u8, this is defined to be 256.
+ */
+#define MAX_INET_PROTOS		256
+
+/* This is used to register protocols. */
+struct net_protocol {
+	int			(*handler)(struct sk_buff *skb);
+
+	/* This returns an error if we weren't able to handle the error. */
+	int			(*err_handler)(struct sk_buff *skb, u32 info);
+
+	unsigned int		no_policy:1,
+				/* does the protocol do more stringent
+				 * icmp tag validation than simple
+				 * socket lookup?
+				 */
+				icmp_strict_tag_validation:1;
+	u32			secret;
+};
+
+#if IS_ENABLED(CONFIG_IPV6)
+struct inet6_protocol {
+	int	(*handler)(struct sk_buff *skb);
+
+	/* This returns an error if we weren't able to handle the error. */
+	int	(*err_handler)(struct sk_buff *skb,
+			       struct inet6_skb_parm *opt,
+			       u8 type, u8 code, int offset,
+			       __be32 info);
+
+	unsigned int	flags;	/* INET6_PROTO_xxx */
+	u32		secret;
+};
+
+#define INET6_PROTO_NOPOLICY	0x1
+#define INET6_PROTO_FINAL	0x2
+#endif
+
+struct net_offload {
+	struct offload_callbacks callbacks;
+	unsigned int		 flags;	/* Flags used by IPv6 for now */
+	u32			 secret;
+};
+/* This should be set for any extension header which is compatible with GSO. */
+#define INET6_PROTO_GSO_EXTHDR	0x1
+
+/* This is used to register socket interfaces for IP protocols.  */
+struct inet_protosw {
+	struct list_head list;
+
+        /* These two fields form the lookup key.  */
+	unsigned short	 type;	   /* This is the 2nd argument to socket(2). */
+	unsigned short	 protocol; /* This is the L4 protocol number.  */
+
+	struct proto	 *prot;
+	const struct proto_ops *ops;
+  
+	unsigned char	 flags;      /* See INET_PROTOSW_* below.  */
+};
+#define INET_PROTOSW_REUSE 0x01	     /* Are ports automatically reusable? */
+#define INET_PROTOSW_PERMANENT 0x02  /* Permanent protocols are unremovable. */
+#define INET_PROTOSW_ICSK      0x04  /* Is this an inet_connection_sock? */
+
+extern struct net_protocol __rcu *inet_protos[MAX_INET_PROTOS];
+extern const struct net_offload __rcu *inet_offloads[MAX_INET_PROTOS];
+extern const struct net_offload __rcu *inet6_offloads[MAX_INET_PROTOS];
+
+#if IS_ENABLED(CONFIG_IPV6)
+extern struct inet6_protocol __rcu *inet6_protos[MAX_INET_PROTOS];
+#endif
+
+int inet_add_protocol(const struct net_protocol *prot, unsigned char num);
+int inet_del_protocol(const struct net_protocol *prot, unsigned char num);
+int inet_add_offload(const struct net_offload *prot, unsigned char num);
+int inet_del_offload(const struct net_offload *prot, unsigned char num);
+void inet_register_protosw(struct inet_protosw *p);
+void inet_unregister_protosw(struct inet_protosw *p);
+
+#if IS_ENABLED(CONFIG_IPV6)
+int inet6_add_protocol(const struct inet6_protocol *prot, unsigned char num);
+int inet6_del_protocol(const struct inet6_protocol *prot, unsigned char num);
+int inet6_register_protosw(struct inet_protosw *p);
+void inet6_unregister_protosw(struct inet_protosw *p);
+#endif
+int inet6_add_offload(const struct net_offload *prot, unsigned char num);
+int inet6_del_offload(const struct net_offload *prot, unsigned char num);
+
+#endif	/* _PROTOCOL_H */