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Commit 32194450 authored by Tom Zanussi's avatar Tom Zanussi Committed by Linus Torvalds
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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: default avatarTom 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 60cadec9

kernel/relay.c

+11 −1
Original line number Diff line number Diff line
@@ -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;

}