linux-kernel - [PATCH] ext4: remove abnormal set for I_DATA

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Message-Id: <1531123108-45918-1-git-send-email-junil0814.lee@lge.com>
Date:   Mon,  9 Jul 2018 16:58:28 +0900
From:   Junil Lee <junil0814.lee@....com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        junil0814.lee@...r.kernel.org, Junil Lee <junil0814.lee@....com>
Subject: [PATCH] ext4: remove abnormal set for I_DATA_SEM subclass

The -EBUSY return value of dquot_enable() function means that just
want to update flags. If some users make a duplicate request to update
flags, lockdep could catch the false positive casued by needing to
allocate a quota block from inside ext4_map_blocks(), while holding
i_data_sem for a data inode. This results in this complaint:

       CPU0                    CPU1
       ----                    ----
  lock(&s->s_dquot.dqio_mutex);
                               lock(&ei->i_data_sem);
                               lock(&s->s_dquot.dqio_mutex);
  lock(&ei->i_data_sem);

Signed-off-by: Junil Lee <junil0814.lee@....com>
---
 fs/ext4/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 13d2706..0757c9a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5637,7 +5637,7 @@ static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
 	lockdep_set_quota_inode(qf_inode, I_DATA_SEM_QUOTA);
 	err = dquot_enable(qf_inode, type, format_id, flags);
 	iput(qf_inode);
-	if (err)
+	if (err && err != -EBUSY)
 		lockdep_set_quota_inode(qf_inode, I_DATA_SEM_NORMAL);
 
 	return err;
-- 
2.6.2