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pipe: fix pipe buffer resizing

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pipe_set_size() needs to copy pipe bufs from the old circular buffer
to the new.

The current code gets this wrong in multiple ways, resulting in oops.

Test program is available here:
  http://www.kernel.org/pub/linux/kernel/people/mszeredi/piperesize/

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Miklos Szeredi 2010-06-08 16:28:45 +02:00 committed by Jens Axboe
parent 3e6c05052c
commit 1d862f4122
1 changed files with 10 additions and 3 deletions
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13
fs/pipe.c
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@ -1145,13 +1145,20 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
* and adjust the indexes.
*/
if (pipe->nrbufs) {
const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
const unsigned int head = pipe->nrbufs - tail;
unsigned int tail;
unsigned int head;
tail = pipe->curbuf + pipe->nrbufs;
if (tail < pipe->buffers)
tail = 0;
else
tail &= (pipe->buffers - 1);
head = pipe->nrbufs - tail;
if (head)
memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
if (tail)
memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
}
pipe->curbuf = 0;