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Subject: Re: [PATCH 1/2] fibmap: Warn and return an error in case of block >
 INT_MAX
To:     Dave Chinner <david@fromorbit.com>
Cc:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Matthew Wilcox <willy@infradead.org>,
        Eric Biggers <ebiggers@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        Jan Kara <jack@suse.com>, tytso@mit.edu,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        linux-ext4@vger.kernel.org
References: <cover.1587670914.git.riteshh@linux.ibm.com>
 <e34d1ac05d29aeeb982713a807345a0aaafc7fe0.1587670914.git.riteshh@linux.ibm.com>
 <20200424191739.GA217280@gmail.com>
 <20200424225425.6521D4C040@d06av22.portsmouth.uk.ibm.com>
 <20200424234058.GA29705@bombadil.infradead.org>
 <20200424234647.GX6749@magnolia>
 <20200425070335.B43334C046@d06av22.portsmouth.uk.ibm.com>
 <20200427010444.GF2040@dread.disaster.area>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Tue, 28 Apr 2020 12:59:56 +0530
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On 4/27/20 6:34 AM, Dave Chinner wrote:
> On Sat, Apr 25, 2020 at 12:33:34PM +0530, Ritesh Harjani wrote:
>>
>>
>> On 4/25/20 5:16 AM, Darrick J. Wong wrote:
>>> On Fri, Apr 24, 2020 at 04:40:58PM -0700, Matthew Wilcox wrote:
>>>> On Sat, Apr 25, 2020 at 04:24:24AM +0530, Ritesh Harjani wrote:
>>>>> Ok, I see.
>>>>> Let me replace WARN() with below pr_warn() line then. If no objections,
>>>>> then will send this in a v2 with both patches combined as Darrick
>>>>> suggested. - (with Reviewed-by tags of Jan & Christoph).
>>>>>
>>>>> pr_warn("fibmap: this would truncate fibmap result\n");
>>>>
>>>> We generally don't like userspace to be able to trigger kernel messages
>>>> on demand, so they can't swamp the logfiles.  printk_ratelimited()?
>>>
>>> Or WARN_ON_ONCE...
>>
>> So, Eric was mentioning WARN_** are mostly for kernel side of bugs.
>> But this is mostly a API fault which affects user side and also to
>> warn the user about the possible truncation in the block fibmap
>> addr.
>> Also WARN_ON_ONCE, will be shown only once and won't be printed for
>> every other file for which block addr > INT_MAX.
>>
>> I think we could go with below. If ok, I could post this in v2.
>>
>> pr_warn_ratelimited("fibmap: would truncate fibmap result\n");
> 
> Please include the process ID, the superblock ID and the task name
> that is triggering this warning. Otherwise the administrator will
> have no clue what is generating it and so won't be able to fix it...
> 
Thanks for the suggestion. I will make it like below then.
Will send a v2 soon.

+		pr_warn_ratelimited("[%s/%d] FS (%s): would truncate fibmap result\n",
+				    current->comm, task_pid_nr(current),
+				    sb->s_id);
+