Re: [PATCH V2] iomap: skip unnecessary ifs_block_is_uptodate check

[Gou Hao]

On 2025/4/10 13:54, Christoph Hellwig wrote:
> On Thu, Apr 10, 2025 at 01:42:23PM +0800, Gou Hao wrote:
> > prior to the loop, $i is either the first !uptodate block, or
> > it's past $last.  Assuming there's no overflow (there's no combination
> > of huge folios and tiny blksize) then yeah, there's no point in
> > retesting that the same block $i is uptodate since we hold the folio
> > lock so nobody else could have set uptodate.
> Capitalize the first word in the sentence and use up the 73 characters
> available for the commit log:
>
> In iomap_adjust_read_range, i is either the first !uptodate block, or it
> is past last for the second loop looking for trailing uptodate blocks.
> Assuming there's no overflow (there's no combination of huge folios and
> tiny blksize) then yeah, there is no point in retesting that the same
> block pointed to by i is uptodate since we hold the folio lock so nobody
> else could have set it uptodate.
Thank you, i will change the log in next patch.
> >   		/* truncate len if we find any trailing uptodate block(s) */
> > -		for ( ; i <= last; i++) {
> > +		for (i++; i <= last; i++) {
> A bit nitpicky, but I find a i++ in the initialization condition of a
> for loop a bit odd.
>
> What about turning this into a:
>
> 		while (++i <= last) {
>
> ?
Yes,  it is better.  I will test this.
>