linux-kernel - Re: [BUG] copy file result with zero

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Message-ID: <CABqxG0eiRiCSirXi5rBB0bJ2AJSQjF2dje2BcjbVYEYWgf-zpw@mail.gmail.com>
Date:	Sun, 2 Oct 2011 07:37:32 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	"Ted Ts'o" <tytso@....edu>, Dave Young <hidave.darkstar@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-ext4@...r.kernel.org
Subject: Re: [BUG] copy file result with zero

On Sat, Oct 1, 2011 at 10:39 PM, Ted Ts'o <tytso@....edu> wrote:
> On Sat, Oct 01, 2011 at 10:01:35PM +0800, Dave Young wrote:
>> Hi,
>>
>> Weird problem, when I build app from source,
>> make; make install
>> run the command, but got "cannot execute binary file"
>>
>> hexdump shows the installed binary is full of zero
>>
>> Is it related to ext4 fiemap problem described below?
>> http://lwn.net/Articles/429349/
>
> There is general agreement that /bin/cp should not have been relying
> on FIEMAP, and I believe the more recent versions of /bin/cp have
> removed that code by default pending implementation of
> SEEK_HOLE/SEEK_DATA.  That being said, ext4 had a workaround to its
> FIEMAP implementation that landed in 2.6.39, and you're using
> 3.1.0-rc6.

Do you means It should work in 3.1.0-rc6 even with cp which depends fiemap?

>
>> I finally managed to find the way to reproduce this:
>> just cp a elf binary A  to file B, then cp B to file C,  then you will get:
>> A == B != C
>>
>> ie.
>> cp /bin/ls ls1
>> cp ls1 ls2
>>
>> ls2 will be filled with zero
>
> If you add a "sync" between the two copies, does that work around the
> problem?  I bet it will...

Yes, it works

>
> My suggestion is to upgrade to a newer version of coreutils that
> doesn't try to use FIEMAP.

Thanks, will try

>
>                                        - Ted
>



-- 
Regards
Dave
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