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([2402:f000:1:1501:200:5efe:a66f:4739]) by smtp.gmail.com with ESMTPSA id k5-v6sm3529657ioc.68.2018.08.13.02.30.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 Aug 2018 02:31:01 -0700 (PDT) Subject: Re: [BUG] mm: truncate: a possible sleep-in-atomic-context bug in truncate_exceptional_pvec_entries() To: Jan Kara Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, ak@linux.intel.com, mawilcox@microsoft.com, viro@zeniv.linux.org.uk, ross.zwisler@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel References: <20180813085635.GA8927@quack2.suse.cz> From: Jia-Ju Bai Message-ID: <91c44d76-ff62-7cdc-3f78-e0c3acc58637@gmail.com> Date: Mon, 13 Aug 2018 17:30:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180813085635.GA8927@quack2.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/8/13 16:56, Jan Kara wrote: > Hi, > > On Mon 13-08-18 11:10:23, Jia-Ju Bai wrote: >> The kernel may sleep with holding a spinlock. >> >> The function call paths (from bottom to top) in Linux-4.16 are: >> >> [FUNC] schedule >> fs/dax.c, 259: schedule in get_unlocked_mapping_entry >> fs/dax.c, 450: get_unlocked_mapping_entry in __dax_invalidate_mapping_entry >> fs/dax.c, 471: __dax_invalidate_mapping_entry in dax_delete_mapping_entry >> mm/truncate.c, 97: dax_delete_mapping_entry in >> truncate_exceptional_pvec_entries >> mm/truncate.c, 82: spin_lock_irq in truncate_exceptional_pvec_entries >> >> I do not find a good way to fix, so I only report. >> This is found by my static analysis tool (DSAC). > Thanks for report but this is a false positive. Note that the lock is > acquired only if we are not operating on DAX mapping but we can get to > dax_delete_mapping_entry() only if we are operating on DAX mapping. Thanks for your reply :) My tool does not well check the path condition here... Sorry for this false report. Best wishes, Jia-Ju Bai