From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 25 Nov 2021 14:05:18 +0100
Subject: fuse: release pipe buf after last use
Git-commit: 473441720c8616dfaf4451f9c7ea14f0eb5e5d65
Patch-mainline: v5.16-rc3
References: bsc#1193318

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>
[luis: adjusted context; use lru_cache_add_file() instead of lru_cache_add() ]
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/fuse/dev.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -899,17 +899,17 @@ 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))