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    Subject[PATCH 4.9 27/62] fuse: release pipe buf after last use
    Date
    From: Miklos Szeredi <mszeredi@redhat.com>

    commit 473441720c8616dfaf4451f9c7ea14f0eb5e5d65 upstream.

    Checking buf->flags should be done before the pipe_buf_release() is called
    on the pipe buffer, since releasing the buffer might modify the flags.

    This is exactly what page_cache_pipe_buf_release() does, and which results
    in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was
    trying to fix.

    Reported-by: Justin Forbes <jmforbes@linuxtx.org>
    Fixes: 712a951025c0 ("fuse: fix page stealing")
    Cc: <stable@vger.kernel.org> # v2.6.35
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fuse/dev.c | 10 +++++-----
    1 file changed, 5 insertions(+), 5 deletions(-)

    --- a/fs/fuse/dev.c
    +++ b/fs/fuse/dev.c
    @@ -898,17 +898,17 @@ static int fuse_try_move_page(struct fus
    goto out_put_old;
    }

    + get_page(newpage);
    +
    + if (!(buf->flags & PIPE_BUF_FLAG_LRU))
    + lru_cache_add_file(newpage);
    +
    /*
    * Release while we have extra ref on stolen page. Otherwise
    * anon_pipe_buf_release() might think the page can be reused.
    */
    pipe_buf_release(cs->pipe, buf);

    - get_page(newpage);
    -
    - if (!(buf->flags & PIPE_BUF_FLAG_LRU))
    - lru_cache_add_file(newpage);
    -
    err = 0;
    spin_lock(&cs->req->waitq.lock);
    if (test_bit(FR_ABORTED, &cs->req->flags))

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