[PATCH] splice: sendfile() at once fails for big files

[Christophe Leroy <christophe.leroy@c-s.fr>]

When big files (over 64kbytes) are sent with sendfile(), they are sent by blocks
of 64kbytes. In that case, the target must be informed that the current block is
not the last one, otherwise if might take wrong actions.
The issue was observed while sending a file to an AF_ALG socket for hashing. The
hash was reset at each 64k block.
This patch adds SPLICE_F_MORE to the flags when more data is pending.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Index: b/fs/splice.c
===================================================================
--- a/fs/splice.c	(revision 5615)
+++ b/fs/splice.c	(working copy)
@@ -1171,7 +1171,7 @@
 	long ret, bytes;
 	umode_t i_mode;
 	size_t len;
-	int i, flags;
+	int i, flags, more;
 
 	/*
 	 * We require the input being a regular file, as we don't want to
@@ -1214,6 +1214,7 @@
 	 * Don't block on output, we have to drain the direct pipe.
 	 */
 	sd->flags &= ~SPLICE_F_NONBLOCK;
+	more = sd->flags & SPLICE_F_MORE;
 
 	while (len) {
 		size_t read_len;
@@ -1226,6 +1227,10 @@
 		read_len = ret;
 		sd->total_len = read_len;
 
+		if (read_len < len)
+			sd->flags |= SPLICE_F_MORE;
+		else if (!more)
+			sd->flags &= ~SPLICE_F_MORE;
 		/*
 		 * NOTE: nonblocking mode only applies to the input. We
 		 * must not do the output in nonblocking mode as then we