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

[Joerg Schilling]

Paul Eggert <address@hidden> wrote:

> On 07/06/2016 04:53 PM, Joerg Schilling wrote:
> > Antonio Diaz Diaz<address@hidden>  wrote:
> >
> >> >Joerg Schilling wrote:
> >>> > >POSIX requires st_blocks to be != 0 in case that the file contains 
> >>> > >data.
> >> >
> >> >Please, could you provide a reference? I can't find such requirement at
> >> >http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_stat.h.html
> >     blkcnt_t st_blocks      Number of blocks allocated for this object.
>
> This doesn't require that st_blocks must be nonzero if the file contains 
> nonzero data, any more that it requires that st_blocks must be nonzero 
> if the file contains zero data. In either case, metadata outside the 
> scope of st_blocks might contain enough information for the file system 
> to represent all the file's data.

In other words, you concur that a delayed assignment of the "correct" value for 
st_blocks while the contend of the file does not change is not permitted.

Jörg

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