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.
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)
