From 32194450330be327f3b25bf6b66298bd122599e9 Mon Sep 17 00:00:00 2001
From: Tom Zanussi <tzanussi@gmail.com>
Date: Tue, 5 Aug 2008 13:01:10 -0700
Subject: relay: fix "full buffer with exactly full last subbuffer" accounting
problem
In relay's current read implementation, if the buffer is completely full
but hasn't triggered the buffer-full condition (i.e. the last write
didn't cross the subbuffer boundary) and the last subbuffer is exactly
full, the subbuffer accounting code erroneously finds nothing available.
This patch fixes the problem.
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Andrea Righi <righi.andrea@gmail.com>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/relay.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
(limited to 'kernel')
diff --git a/kernel/relay.c b/kernel/relay.c
index 04006ef970b..8d13a7855c0 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -944,6 +944,10 @@ static void relay_file_read_consume(struct rchan_buf *buf,
size_t n_subbufs = buf->chan->n_subbufs;
size_t read_subbuf;
+ if (buf->subbufs_produced == buf->subbufs_consumed &&
+ buf->offset == buf->bytes_consumed)
+ return;
+
if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
relay_subbufs_consumed(buf->chan, buf->cpu, 1);
buf->bytes_consumed = 0;
@@ -975,6 +979,8 @@ static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
relay_file_read_consume(buf, read_pos, 0);
+ consumed = buf->subbufs_consumed;
+
if (unlikely(buf->offset > subbuf_size)) {
if (produced == consumed)
return 0;
@@ -993,8 +999,12 @@ static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
if (consumed > produced)
produced += n_subbufs * subbuf_size;
- if (consumed == produced)
+ if (consumed == produced) {
+ if (buf->offset == subbuf_size &&
+ buf->subbufs_produced > buf->subbufs_consumed)
+ return 1;
return 0;
+ }
return 1;
}
--
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