Re: [syzbot] Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback

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Subject: Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback
Author: lizhi.xu@xxxxxxxxxxxxx

add file refconut when add fid to list

#syz test: upstream c0ecd6388360

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index de009a33e0e2..b7016e148f48 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
+#include <linux/file.h>
 
 #include "v9fs.h"
 #include "v9fs_vfs.h"
@@ -95,6 +96,7 @@ void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
 	struct p9_fid *fid = *pfid;
 
 	spin_lock(&inode->i_lock);
+	fget(fid->fid);
 	hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
 	spin_unlock(&inode->i_lock);