Re: [PATCH 1/3] fs: add SEEK_HOLE and SEEK_DATA flags V4

[Sunil Mushran]

On 05/25/2011 01:46 PM, Josef Bacik wrote:
> On 05/25/2011 03:45 PM, Andreas Dilger wrote:
> > Most of the filesystem-specific ->llseek() methods don't do any error
> > checking on "origin" because this is handled at the sys_llseek() level,
> > and hasn't changed in many years.
> >
> > I assume this patch is also dependent upon the "remove default_llseek()"
> > patch, so that the implementation of SEEK_DATA and SEEK_HOLE can be done
> > in only generic_file_llseek()?
> >
> > Finally, while looking through the various ->llseek() methods I notice
> > that many filesystems return "i_size" for SEEK_END, which clearly does
> > not make sense for filesystems like ext3/ext4 htree, btrfs, etc that
> > use hash keys instead of byte offsets for doing directory traversal.
> > The comment at generic_file_llseek() is that it is intended for use by
> > regular files.
> >
> > Should the ext4_llseek() code be changed to return 0x7ffffffff for the
> > SEEK_END value?  That makes more sense compared to values returned for
> > SEEK_CUR so that an application can compare the current "offset" with
> > the final value for a progress bar.
> So maybe we make SEEK_DATA/SEEK_HOLE only work on regular files and not
> directories?  Sunil what does solaris do?  Thanks,

In Solaris the size of the directory appears to be equal to the number
of entries and the offset is the file#, so to speak. SEEK_DATA returns
the current offset and SEEK_HOLE the last one.

Just to be clear, I am not a Solaris expert. I just happen to have access
to it. ;)
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