Re: [BUG] copy file result with zero

Jeff liu
2011-10-02T06:41:26Z

> On Sat, Oct 1, 2011 at 10:39 PM, Ted Ts'o <tytso@mit.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.

Actually, upstream cp(1) using FIEMAP only if the source file is sparse, or else, it will do normal copy, i.e, block based.

Thanks,
-Jeff
>
> 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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