On 4/13/26 21:20, Zi Yan wrote: > collapse_file() requires FSes supporting large folio with at least > PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. > MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem. > > While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE. > > In collapse_scan_file(), add FS eligibility check to avoid redundant scans. > > Signed-off-by: Zi Yan <[email protected]> > --- > mm/khugepaged.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index b8452dbdb043..d2f0acd2dac2 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1892,8 +1892,9 @@ static enum scan_result collapse_file(struct mm_struct > *mm, unsigned long addr, > int nr_none = 0; > bool is_shmem = shmem_file(file); > > - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); > - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); > + /* MADV_COLLAPSE ignores shmem huge config, so do not check shmem */ > + VM_WARN_ON_ONCE(!is_shmem && mapping_max_folio_order(mapping) < > PMD_ORDER); > + VM_WARN_ON_ONCE(start & (HPAGE_PMD_NR - 1)); > > result = alloc_charge_folio(&new_folio, mm, cc); > if (result != SCAN_SUCCEED) > @@ -2321,6 +2322,13 @@ static enum scan_result collapse_scan_file(struct > mm_struct *mm, > int node = NUMA_NO_NODE; > enum scan_result result = SCAN_SUCCEED; > > + /* > + * skip files without PMD-order folio support > + * do not check shmem, since MADV_COLLAPSE ignores shmem huge config > + */
How is the !collapse path handled? Through thp_vma_allowable_order() in collapse_scan_mm_slot()? Wouldn't it be better to have that check exactly there? -- Cheers, David
