Re: [PATCH v4] btrfs: trim: fix underflow in trim length to prevent access beyond device boundary

[David Sterba <dsterba@suse.cz>]

On Wed, Aug 12, 2020 at 02:33:33PM +0800, Qu Wenruo wrote:
> 
> 
> On 2020/8/12 下午2:10, David Sterba wrote:
> > On Tue, Aug 11, 2020 at 03:42:31PM +0800, Qu Wenruo wrote:
> >>>> CHUNK_TRIMMED and CHUNK_ALLOCATED.
> >>>>
> >>>> Thus what we're doing is to clear all utilized bits.
> >>>
> >>> Which is true for now, adding a new bit would change that.
> >>
> >> Yep, that's also why I had the comment here.
> >
> > The comment is not enough to make the code future proof, as we really
> > want do clear all bits in the range beyond device->total_size and that
> > works only if we specify them all (clear_state_bit).
> >
> > Either we can define a bitmask of all the bits next to their definition
> > (slightly more error prone if we forget to add that manually), or pass a
> > all ones to the clear_extent_bit. Though this is a bit uncommon, with a
> > comment I'd prefer this option.
> 
> OK, I'd go that (u64)-1 as clear_bits direction, with updated comment.

Hold, on, I'm sending out v5 that I'm about to commit.