linux-kernel - Re: [syzbot] [nilfs?] possible deadlock in nilfs_dirty

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Message-ID: <tencent_97F875737633662A3CB3362E968E37E44A09@qq.com>
Date: Sun, 20 Oct 2024 11:36:05 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+9ef37ac20608f4836256@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [nilfs?] possible deadlock in nilfs_dirty_inode (4)

make sure all allocations with GFP_NOFS

#syz test

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index be6acf6e2bfc..183c16ad8776 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -252,11 +252,14 @@ static int nilfs_write_begin(struct file *file, struct address_space *mapping,
 {
 	struct inode *inode = mapping->host;
 	int err = nilfs_transaction_begin(inode->i_sb, NULL, 1);
+	unsigned flags;
 
 	if (unlikely(err))
 		return err;
 
+	flags = memalloc_nofs_save();
 	err = block_write_begin(mapping, pos, len, foliop, nilfs_get_block);
+	memalloc_nofs_restore(flags);
 	if (unlikely(err)) {
 		nilfs_write_failed(mapping, pos + len);
 		nilfs_transaction_abort(inode->i_sb);