On Tue, 11 Apr 2023 04:40:17 +0100 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > On Thu, Apr 06, 2023 at 07:28:44PM -0700, Vishal Moola wrote: > > > - flush_dcache_page(subpage); > > > - > > > cond_resched(); > > > } > > > + flush_dcache_folio(dst_folio); > > > return ret_val; > > > } > > > > Moving the flush_dcache_page() outside the loop to be > > flush_dcache_folio() changes the behavior of the function. > > > > Initially, if it fails to copy the entire page, the function breaks out > > of the loop and returns the number of unwritten bytes without > > flushing the page from the cache. Now if it fails, it will still flush > > out the page it failed on, as well as any later pages it may not > > have gotten to yet. > > I'm not sure this is worth worrying about. Failing to copy the entire > folio is unlikely, and if we do, flushing the entire folio instead of just > a few pages in it is harmless. Plus I have patches which significantly > optiise flush_dcache_folio() over flush_dcache_page() (for the majority > of architectures) and so I think this change is actually beneficial in > the long term. Thanks, I'll send the series in for the next merge window as-is. If others remain unhappy with the flushing issue, please propose something during the next -rc cycle.
