Re: [PATCH RFCv2] new ioctl TREE_SEARCH_V2

[Goffredo Baroncelli <kreijack@libero.it>]

Hi,

On 2014-01-27 14:28, Gerhard Heift wrote:
> This patch series adds a new ioctl TREE_SEARCH_V2 with which we could store the
> results in a varying buffer. Now even items larger than 3992 bytes or a large
> amount of items can be returned.


One of the main strangeness of the current TREE_SEARCH ioctl, which I
found is the fact that the search was not in a "rectangular" region, but
in a "linear" region.

This is due the fact that after a ioctl call, we have to set the min_*
fields with the sh->{objectid,offset,type} +1 rounding to 0 if case of
overflow.

This because the min_* fields are both the "lower bound" of the search
and the "starting point" of the next search. Adding a new set of fields
named start_* could solve this issue.

I discussed this topic few years ago in [1].

Because we are introducing a new ioctl, is it possible to solve this
issue ? We could avoid some userspace<->kernelspace transition, which
seems be one of the goal of your patch.

BR
G.Baroncelli



[1] http://www.spinics.net/lists/linux-btrfs/msg07617.html



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