From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Wed, 27 Jun 2007 21:10:04 +0000 (-0700)
Subject: relayfs: fix overwrites
X-Git-Tag: firefly_0821_release~28543
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a66e356c04ece4a96f44b942b68234c3de8ec3f5;p=firefly-linux-kernel-4.4.55.git

relayfs: fix overwrites

When I use relayfs with "overwrite" mode, read() still sets incorrect
number of consumed bytes.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Tom Zanussi <zanussi@us.ibm.com>
Acked-by: David Wilder <dwilder@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/relay.c b/kernel/relay.c
index e61156ea4e25..95db8c79fe8f 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -812,7 +812,10 @@ static void relay_file_read_consume(struct rchan_buf *buf,
 	}
 
 	buf->bytes_consumed += bytes_consumed;
-	read_subbuf = read_pos / buf->chan->subbuf_size;
+	if (!read_pos)
+		read_subbuf = buf->subbufs_consumed % n_subbufs;
+	else
+		read_subbuf = read_pos / buf->chan->subbuf_size;
 	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 		if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 		    (buf->offset == subbuf_size))
@@ -841,8 +844,9 @@ static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 	}
 
 	if (unlikely(produced - consumed >= n_subbufs)) {
-		consumed = (produced / n_subbufs) * n_subbufs;
+		consumed = produced - n_subbufs + 1;
 		buf->subbufs_consumed = consumed;
+		buf->bytes_consumed = 0;
 	}
 	
 	produced = (produced % n_subbufs) * subbuf_size + buf->offset;