From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 10608410D37 for ; Sat, 28 Feb 2026 10:53:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772276025; cv=none; b=u5U4Hh7RlrDKYmqIxrHiTIWV25/+2ADtWmYhuc2WPJ70i4F/bb0Bn1CfBAqutCuVkfDrU+/EwImg0Yc4VMt1D/4uhUqRPlvoHYZDLMUIWX1jposPVL+47W4BA1XWOlG609VFJKOiliPe7T2uNcVUqgMIge4BaXTB8EmkT9+w7dU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772276025; c=relaxed/simple; bh=mp37iUT9CBPceUfxJWxzhIYhKDxI0SY/LttS6rzHmzk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pDz1fgCU+hlycEYb2UCLqH3gpAqJWGPBn94hby+b0GG7Wh2NBj2Qq97VbxCY9PYcx8yxCgyUU0EELudblJOMb5P4zxYOtoV8EvFhgzvRPA+3/UMA09AJf0UfnRNWJJczrsId43bvB43NcQ46JigvS73zS29WMuhf0/JbZj7D6ac= ARC-Authentication-Results:i=1; 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Sat, 28 Feb 2026 18:53:34 +0800 Message-ID: Date: Sat, 28 Feb 2026 18:53:34 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ocfs2: fix deadlock when creating quota file To: Heming Zhao Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, activprithvi@gmail.com, syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com References: <20260224084909.28361-1-heming.zhao@suse.com> From: Joseph Qi In-Reply-To: <20260224084909.28361-1-heming.zhao@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/24/26 4:48 PM, Heming Zhao wrote: > syzbot detected a circular locking dependency. the scenarios: > > CPU0 CPU1 > ---- ---- > lock(&ocfs2_quota_ip_alloc_sem_key); > lock(&ocfs2_sysfile_lock_key[USER_QUOTA_SYSTEM_INODE]); > lock(&ocfs2_quota_ip_alloc_sem_key); > lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]); > > or: > CPU0 CPU1 > ---- ---- > lock(&ocfs2_quota_ip_alloc_sem_key); > lock(&dquot->dq_lock); > lock(&ocfs2_quota_ip_alloc_sem_key); > lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]); > > Following are the code paths for above scenarios: > > path_openat > ocfs2_create > ocfs2_mknod > + ocfs2_reserve_new_inode > | ocfs2_reserve_suballoc_bits > | inode_lock(alloc_inode) //C0: hold INODE_ALLOC_SYSTEM_INODE > | //at end of this func, ocfs2_free_alloc_context(inode_ac) calls inode_unlock > | > + ocfs2_get_init_inode > __dquot_initialize > dqget > ocfs2_acquire_dquot > + ocfs2_lock_global_qf > | down_write(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem)//A2:grabbing > + ocfs2_create_local_dquot > down_write(&OCFS2_I(lqinode)->ip_alloc_sem)//A3:grabbing > > evict > ocfs2_evict_inode > ocfs2_delete_inode > ocfs2_wipe_inode > + inode_lock(orphan_dir_inode) //B0:hold > + ... > + ocfs2_remove_inode > inode_lock(inode_alloc_inode) //INODE_ALLOC_SYSTEM_INODE > down_write(&inode->i_rwsem) //C1:grabbing > > generic_file_direct_write > ocfs2_direct_IO > __blockdev_direct_IO > dio_complete > ocfs2_dio_end_io > ocfs2_dio_end_io_write > + down_write(&oi->ip_alloc_sem) //A0:hold > + ocfs2_del_inode_from_orphan > inode_lock(orphan_dir_inode) //B1:grabbing > > Root cause for the circular locking: > > DIO completion path: > holds oi->ip_alloc_sem and is trying to acquire the orphan_dir_inode lock. > > evict path: > holds the orphan_dir_inode lock and is trying to acquire the > inode_alloc_inode lock. > > ocfs2_mknod path: > Holds the inode_alloc_inode lock (to allocate a new quota file) and is > blocked waiting for oi->ip_alloc_sem in ocfs2_acquire_dquot(). > > How to fix: > > Replace down_write() with down_write_trylock() in ocfs2_acquire_dquot(). > If acquiring oi->ip_alloc_sem fails, return -EBUSY to abort the file creation > routine and break the deadlock. > > Reported-by: syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=78359d5fbb04318c35e9 > Signed-off-by: Heming Zhao > --- > fs/ocfs2/quota_global.c | 5 ++++- > fs/ocfs2/quota_local.c | 5 ++++- > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c > index e85b1ccf81be..4321d8f59402 100644 > --- a/fs/ocfs2/quota_global.c > +++ b/fs/ocfs2/quota_global.c > @@ -311,7 +311,10 @@ int ocfs2_lock_global_qf(struct ocfs2_mem_dqinfo *oinfo, int ex) > spin_unlock(&dq_data_lock); > if (ex) { > inode_lock(oinfo->dqi_gqinode); > - down_write(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem); > + if (!down_write_trylock(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem)) { > + inode_unlock(oinfo->dqi_gqinode); You've missed the oinfo->dqi_gqinode cleanup. > + return -EBUSY; > + } > } else { > down_read(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem); > } > diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c > index c4e0117d8977..e451f3d96037 100644 > --- a/fs/ocfs2/quota_local.c > +++ b/fs/ocfs2/quota_local.c > @@ -1224,7 +1224,10 @@ int ocfs2_create_local_dquot(struct dquot *dquot) > int status; > u64 pcount; > > - down_write(&OCFS2_I(lqinode)->ip_alloc_sem); > + if (!down_write_trylock(&OCFS2_I(lqinode)->ip_alloc_sem)) { > + status = -EBUSY; > + goto out; We cannot goto out here since it does up_write. It seems we can return EBUSY directly. Joseph > + } > chunk = ocfs2_find_free_entry(sb, type, &offset); > if (!chunk) { > chunk = ocfs2_extend_local_quota_file(sb, type, &offset);