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, 50 insertions, 0 deletions

diff --git a/include/net/esp.h b/include/net/esp.h
new file mode 100644
index 000000000..322950727
--- /dev/null
+++ b/include/net/esp.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_ESP_H
+#define _NET_ESP_H
+
+#include <linux/skbuff.h>
+
+struct ip_esp_hdr;
+struct xfrm_state;
+
+static inline struct ip_esp_hdr *ip_esp_hdr(const struct sk_buff *skb)
+{
+	return (struct ip_esp_hdr *)skb_transport_header(skb);
+}
+
+static inline void esp_output_fill_trailer(u8 *tail, int tfclen, int plen, __u8 proto)
+{
+	/* Fill padding... */
+	if (tfclen) {
+		memset(tail, 0, tfclen);
+		tail += tfclen;
+	}
+	do {
+		int i;
+		for (i = 0; i < plen - 2; i++)
+			tail[i] = i + 1;
+	} while (0);
+	tail[plen - 2] = plen - 2;
+	tail[plen - 1] = proto;
+}
+
+struct esp_info {
+	struct	ip_esp_hdr *esph;
+	__be64	seqno;
+	int	tfclen;
+	int	tailen;
+	int	plen;
+	int	clen;
+	int 	len;
+	int 	nfrags;
+	__u8	proto;
+	bool	inplace;
+};
+
+int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp);
+int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp);
+int esp_input_done2(struct sk_buff *skb, int err);
+int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp);
+int esp6_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp);
+int esp6_input_done2(struct sk_buff *skb, int err);
+#endif