The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 473441720c8616dfaf4451f9c7ea14f0eb5e5d65 Mon Sep 17 00:00:00 2001

From: Miklos Szeredi mszeredi@redhat.com Date: Thu, 25 Nov 2021 14:05:18 +0100 Subject: [PATCH] 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 79f7eda49e06..cd54a529460d 100644 --- 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))