Re: [PATCH v2] btrfs-progs: cmds: Add subcommand that dumps file extents

[Sidong Yang <realwakka@gmail.com>]

On Mon, Jul 12, 2021 at 02:46:39PM +0800, Qu Wenruo wrote:
> 
> 
> On 2021/7/12 下午2:40, Sidong Yang wrote:
> [...]
> > > > +	sk->max_offset = UINT64_MAX;
> > > > +	sk->min_transid = 0;
> > > > +	sk->max_transid = UINT64_MAX;
> > > > +	sk->min_type = sk->max_type = BTRFS_EXTENT_DATA_KEY;
> > > > +	sk->nr_items = 4096;
> > > 
> > > You may want to do the tree search ioctl in a loop, as it's pretty common
> > > for super large or heavily fragmented inode to have way more items than one
> > > ioctl can return.
> > 
> > I don't think much about this. I wonder if it's proper way to search
> > tree. is there any better way than this code?
> 
> Here is one example:
> 
> https://github.com/kilobyte/compsize/blob/master/compsize.c#L179
> 
> It goes @again label to restart from last offset + 1.

Thanks, I read the code you provided. It seems that compsize is also
doing to what this patch do. 

The 'do_file' function checks if nr_items is larger than 512. I wonder
that the number '512' is such an magic number. I'll check it by my own
effort. 

Thanks,
Sidong

> 
> Thanks,
> Qu
>