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, 68 insertions, 0 deletions

diff --git a/include/net/sctp/ulpqueue.h b/include/net/sctp/ulpqueue.h
new file mode 100644
index 000000000..60f664129
--- /dev/null
+++ b/include/net/sctp/ulpqueue.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SCTP kernel implementation
+ * (C) Copyright IBM Corp. 2001, 2004
+ * Copyright (c) 1999-2000 Cisco, Inc.
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001 Intel Corp.
+ * Copyright (c) 2001 Nokia, Inc.
+ * Copyright (c) 2001 La Monte H.P. Yarroll
+ *
+ * These are the definitions needed for the sctp_ulpq type.  The
+ * sctp_ulpq is the interface between the Upper Layer Protocol, or ULP,
+ * and the core SCTP state machine.  This is the component which handles
+ * reassembly and ordering.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email addresses:
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *   Jon Grimm             <jgrimm@us.ibm.com>
+ *   La Monte H.P. Yarroll <piggy@acm.org>
+ *   Sridhar Samudrala     <sri@us.ibm.com>
+ */
+
+#ifndef __sctp_ulpqueue_h__
+#define __sctp_ulpqueue_h__
+
+/* A structure to carry information to the ULP (e.g. Sockets API) */
+struct sctp_ulpq {
+	char pd_mode;
+	struct sctp_association *asoc;
+	struct sk_buff_head reasm;
+	struct sk_buff_head reasm_uo;
+	struct sk_buff_head lobby;
+};
+
+/* Prototypes. */
+void sctp_ulpq_init(struct sctp_ulpq *ulpq, struct sctp_association *asoc);
+void sctp_ulpq_flush(struct sctp_ulpq *ulpq);
+void sctp_ulpq_free(struct sctp_ulpq *);
+
+/* Add a new DATA chunk for processing. */
+int sctp_ulpq_tail_data(struct sctp_ulpq *, struct sctp_chunk *, gfp_t);
+
+/* Add a new event for propagation to the ULP. */
+int sctp_ulpq_tail_event(struct sctp_ulpq *, struct sk_buff_head *skb_list);
+
+/* Renege previously received chunks.  */
+void sctp_ulpq_renege(struct sctp_ulpq *, struct sctp_chunk *, gfp_t);
+
+/* Perform partial delivery. */
+void sctp_ulpq_partial_delivery(struct sctp_ulpq *, gfp_t);
+
+/* Abort the partial delivery. */
+void sctp_ulpq_abort_pd(struct sctp_ulpq *, gfp_t);
+
+/* Clear the partial data delivery condition on this socket. */
+int sctp_clear_pd(struct sock *sk, struct sctp_association *asoc);
+
+/* Skip over an SSN. */
+void sctp_ulpq_skip(struct sctp_ulpq *ulpq, __u16 sid, __u16 ssn);
+
+void sctp_ulpq_reasm_flushtsn(struct sctp_ulpq *, __u32);
+
+__u16 sctp_ulpq_renege_list(struct sctp_ulpq *ulpq,
+			    struct sk_buff_head *list, __u16 needed);
+
+#endif /* __sctp_ulpqueue_h__ */