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Subject: Re: [PATCH 1/2] fibmap: Warn and return an error in case of block >
 INT_MAX
To:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Matthew Wilcox <willy@infradead.org>,
        Eric Biggers <ebiggers@kernel.org>
Cc:     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
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 <20200424191739.GA217280@gmail.com>
 <20200424225425.6521D4C040@d06av22.portsmouth.uk.ibm.com>
 <20200424234058.GA29705@bombadil.infradead.org>
 <20200424234647.GX6749@magnolia>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Sat, 25 Apr 2020 12:33:34 +0530
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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");

-ritesh