Re: [Bug-tar] stat() on btrfs reports the st_blocks with delay (data loss in archivers)

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2016-07-06 12:05, Austin S. Hemmelgarn wrote:
> On 2016-07-06 11:22, Joerg Schilling wrote:
>> "Austin S. Hemmelgarn" <ahferroin7@gmail.com> wrote:
>>
>>>> It should be obvious that a file that offers content also has
>>>> allocated blocks.
>>> What you mean then is that POSIX _implies_ that this is the case, but
>>> does not say whether or not it is required.  There are all kinds of
>>> counterexamples to this too, procfs is a POSIX compliant filesystem
>>> (every POSIX certified system has it), yet does not display the behavior
>>> that you expect, every single file in /proc for example reports 0 for
>>> both st_blocks and st_size, and yet all of them very obviously have
>>> content.
>>
>> You are mistaken.
>>
>> stat /proc/$$/as
>>   File: `/proc/6518/as'
>>   Size: 2793472         Blocks: 5456       IO Block: 512    regular file
>> Device: 5440000h/88342528d      Inode: 7557        Links: 1
>> Access: (0600/-rw-------)  Uid: (   xx/   joerg)   Gid: (  xx/      bs)
>> Access: 2016-07-06 16:33:15.660224934 +0200
>> Modify: 2016-07-06 16:33:15.660224934 +0200
>> Change: 2016-07-06 16:33:15.660224934 +0200
>>
>> stat /proc/$$/auxv
>>   File: `/proc/6518/auxv'
>>   Size: 168             Blocks: 1          IO Block: 512    regular file
>> Device: 5440000h/88342528d      Inode: 7568        Links: 1
>> Access: (0400/-r--------)  Uid: (   xx/   joerg)   Gid: (  xx/      bs)
>> Access: 2016-07-06 16:33:15.660224934 +0200
>> Modify: 2016-07-06 16:33:15.660224934 +0200
>> Change: 2016-07-06 16:33:15.660224934 +0200
>>
>> Any correct implementation of /proc returns the expected numbers in
>> st_size as
>> well as in st_blocks.
> Odd, because I get 0 for both values on all the files in /proc/self and
> all the top level files on all kernels I tested prior to sending that
> e-mail, for reference, they include:
> * A direct clone of HEAD on torvalds/linux
> * 4.6.3 mainline
> * 4.1.27 mainline
> * 4.6.3 mainline with a small number of local patches on top
> * 4.1.19+ from the Raspberry Pi foundation
> * 4.4.6-gentoo (mainline with Gentoo patches on top)
> * 4.5.5-linode69 (not certain about the patches on top)
Further ones I've now tested that behave like the others listed above:
* 2.4.20-8 from RedHat 9
* 2.6.18-1.2798.fc6 from Fedora Core 6
* 3.11.10-301.fc20 from Fedora 20

IOW, it looks like whatever you're running is an exception here.