linux-ext4 - Re: ext4 iomap SEEK broken [was: [GIT PULL] ext4 updates for 4.15]

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Message-ID: <20180212161026.GA2087@thunk.org>
Date:   Mon, 12 Feb 2018 11:10:26 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: ext4 iomap SEEK broken [was: [GIT PULL] ext4 updates for 4.15]

On Mon, Feb 12, 2018 at 01:14:07PM +0100, Jiri Slaby wrote:
> On 02/12/2018, 11:02 AM, Jiri Slaby wrote:
> > Given this happens only on 32bit kernel, I assume some 32bit overflow.
> > But I am unable to see it (yet).
> 
> Just to add, a diff of strace in good and bad kernels:
> @@ -655,14 +655,4 @@
>  _llseek(3, 4275568640, [4286054400], SEEK_DATA) = 0
>  _llseek(3, 4286054400, [4288675840], SEEK_HOLE) = 0
>  _llseek(3, 4288675840, [4299161600], SEEK_DATA) = 0
> -_llseek(3, 4299161600, [4301783040], SEEK_HOLE) = 0
> +_llseek(3, 4299161600, [4299161600], SEEK_HOLE) = 2621440
> 
> llseek returns a very invalid value when it comes to 0x100400000.

Thanks for the bugreport!  Can you send me the output of "filefrag -v"
on the file so I can make sure we can exactly replicate what you're
seeing?

Thanks,

						- Ted