The patch titled
Subject: kernel/relay.c: fix read_pos error when multiple readers
has been added to the -mm tree. Its filename is
kernel-relayc-fix-read_pos-error-when-multiple-readers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-relayc-fix-read_pos-error-when-multiple-readers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-relayc-fix-read_pos-error-when-multiple-readers.patch
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------------------------------------------------------
From: Pengcheng Yang <yangpc@xxxxxxxxxx>
Subject: kernel/relay.c: fix read_pos error when multiple readers
When reading, read_pos should start with bytes_consumed,
not file->f_pos. Because when there is more than one reader,
the read_pos corresponding to file->f_pos may have been consumed,
which will cause the data that has been consumed to be read
and the bytes_consumed update error.
Link: http://lkml.kernel.org/r/1579691175-28949-1-git-send-email-yangpc@xxxxxxxxxx
Signed-off-by: Pengcheng Yang <yangpc@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/relay.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
--- a/kernel/relay.c~kernel-relayc-fix-read_pos-error-when-multiple-readers
+++ a/kernel/relay.c
@@ -991,14 +991,14 @@ static void relay_file_read_consume(stru
/*
* relay_file_read_avail - boolean, are there unconsumed bytes available?
*/
-static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
+static int relay_file_read_avail(struct rchan_buf *buf)
{
size_t subbuf_size = buf->chan->subbuf_size;
size_t n_subbufs = buf->chan->n_subbufs;
size_t produced = buf->subbufs_produced;
size_t consumed = buf->subbufs_consumed;
- relay_file_read_consume(buf, read_pos, 0);
+ relay_file_read_consume(buf, 0, 0);
consumed = buf->subbufs_consumed;
@@ -1059,23 +1059,20 @@ static size_t relay_file_read_subbuf_ava
/**
* relay_file_read_start_pos - find the first available byte to read
- * @read_pos: file read position
* @buf: relay channel buffer
*
- * If the @read_pos is in the middle of padding, return the
+ * If the read_pos is in the middle of padding, return the
* position of the first actually available byte, otherwise
* return the original value.
*/
-static size_t relay_file_read_start_pos(size_t read_pos,
- struct rchan_buf *buf)
+static size_t relay_file_read_start_pos(struct rchan_buf *buf)
{
size_t read_subbuf, padding, padding_start, padding_end;
size_t subbuf_size = buf->chan->subbuf_size;
size_t n_subbufs = buf->chan->n_subbufs;
size_t consumed = buf->subbufs_consumed % n_subbufs;
+ size_t read_pos = consumed * subbuf_size + buf->bytes_consumed;
- if (!read_pos)
- read_pos = consumed * subbuf_size + buf->bytes_consumed;
read_subbuf = read_pos / subbuf_size;
padding = buf->padding[read_subbuf];
padding_start = (read_subbuf + 1) * subbuf_size - padding;
@@ -1131,10 +1128,10 @@ static ssize_t relay_file_read(struct fi
do {
void *from;
- if (!relay_file_read_avail(buf, *ppos))
+ if (!relay_file_read_avail(buf))
break;
- read_start = relay_file_read_start_pos(*ppos, buf);
+ read_start = relay_file_read_start_pos(buf);
avail = relay_file_read_subbuf_avail(read_start, buf);
if (!avail)
break;
_
Patches currently in -mm which might be from yangpc@xxxxxxxxxx are
kernel-relayc-fix-read_pos-error-when-multiple-readers.patch
