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>

1 files changed, 6 insertions, 2 deletions

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;