fuse: release pipe buf after last use

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>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 79f7eda..cd54a52 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -847,17 +847,17 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 
        replace_page_cache_page(oldpage, newpage);
 
+       get_page(newpage);
+
+       if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+               lru_cache_add(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(newpage);
-
        err = 0;
        spin_lock(&cs->req->waitq.lock);
        if (test_bit(FR_ABORTED, &cs->req->flags))