On Thu, Apr 30, 2026 at 12:04:26PM +0800, Barry Song (Xiaomi) wrote: > If we are waiting for long I/O to complete, it makes sense to > avoid holding locks for too long. However, if the folio is > uptodate, we are likely only waiting for a concurrent PTE > update to finish. Retrying the entire page fault seems > excessive.
I think the idea is good, but the implementation is misplaced. The check for folio_uptodate() should be inside folio_lock_or_retry() rather than tampering with FAULT_FLAG_ALLOW_RETRY in its caller. Similarly for your next patch. > Signed-off-by: Barry Song (Xiaomi) <[email protected]> > --- > mm/memory.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 0c740ca363cc..a2e4f2d87ec8 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4949,6 +4949,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > } > > swapcache = folio; > + /* > + * If the folio is uptodate, we are likely only waiting for > + * another concurrent PTE mapping to complete, which should > + * be brief. No need to drop the lock and retry the fault. > + */ > + if (folio_test_uptodate(folio)) > + vmf->flags &= ~FAULT_FLAG_ALLOW_RETRY; > ret |= folio_lock_or_retry(folio, vmf); > if (ret & VM_FAULT_RETRY) { > if (fault_flag_allow_retry_first(vmf->flags) && > -- > 2.39.3 (Apple Git-146) > >
