On Mon, 10 Feb 2025 18:09:48 +0800 I Hsin Cheng <richard120310@xxxxxxxxx> wrote: > When !start_pte is true, the branch for "start_pte" in "out_ptl" label > section is surely false, and "ptl != pml" must be true since "ptl" is > NULL in this case. > > It means both branches in "out_ptl" are redundant, only one thing to be > done is to unlock "pml", make it directly unlock "pml" and return in > this case. Hopefully the compiler will skip the `if (start_pte)' test. Generally, we try to avoid multiple function return points. We could do --- a/mm/pt_reclaim.c~mm-pgtable-unlock-pml-without-branches-when-start_pte +++ a/mm/pt_reclaim.c @@ -43,7 +43,7 @@ void try_to_free_pte(struct mm_struct *m pml = pmd_lock(mm, pmd); start_pte = pte_offset_map_rw_nolock(mm, pmd, addr, &pmdval, &ptl); if (!start_pte) - goto out_ptl; + goto out_unlock; if (ptl != pml) spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); @@ -67,5 +67,6 @@ out_ptl: if (start_pte) pte_unmap_unlock(start_pte, ptl); if (ptl != pml) +out_unlock: spin_unlock(pml); } _ but that's really ugly.
